# Use the compilers

The LLVM compilers translate C and C++ programs into Hexagon processor code.

C and C++ programs are stored in source files, which are text files created with a text editor. Hexagon processor code is stored in object files, which are executable binary files.

## Start the compilers

To start the C compiler from the command line, enter:

hexagon-clang [<options...>] <input_files...>
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To start the C++ compiler from the command line, enter:

hexagon-clang++ [<options...>] <input_files...>
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The compilers accept one or more input files on the command line. Input files can be C/C++ source files or object files. For example:

hexagon-clang hello.c mylib.c
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Command switches are used to control various compiler options (see [Compiler options](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compilers-compiler-options)). A switch consists of a dashcharacter (`-`) followed by a switch name and optional parameter.

Switches are case-sensitive and must be separated by at least one space. For example:

hexagon-clang hello.c -o hello
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To list the available command options, use the –help option:

hexagon-clang --help
    hexagon-clang++ --help
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This option causes the compiler to display the command line syntax, followed by a list of the available command options. clang is the name of the front-end driver for the LLVM framework.

## Input and output files

The LLVM compilers preprocess and compile one or more source files into object files. The compilers then invoke the linker to combine the object files into an executable file.

Following are the input file types and the tool that processes files of each type. The compilers use the filename extension to determine how to process the file.

| Extension\*\* | Description\*\* | Tool\*\* |
| --- | --- | --- |
| `.c` | C source file | C compiler |
| `.i` | C preprocessed file | C compiler |
| `.h` | C header file | C compiler |
| `.cc` | C++ source file | C++ compiler |
| `.cp` | C++ source file | C++ compiler |
| `.cxx` | C++ source file | C++ compiler |
| `.cpp` | C++ source file | C++ compiler |
| `.CPP` | C++ source file | C++ compiler |
| `.c++` | C++ source file | C++ compiler |
| `.C` | C++ source file | C++ compiler |
| `.ii` | C++ preprocessed file | C++ compiler |
| `.h` | C++ header file | C++ compiler |
| `.hh` | C++ header file | C++ compiler |
| `.H` | C++ header file | C++ compiler |
| `.s` | Assembly source file | Assembler |
| `.S` | Assembly source file | Assembler |
| Other | Binary object file | Linker |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |
|  |  |  |

All filename extensions are case-sensitive literal strings. Input files with unrecognized extensions are treated as object files. For more information on assembly and object files, see the *Qualcomm Hexagon Utilities User Guide* (80-N2040-15).

Following are the output file types and the tools used to generate each file type. Compiler options (see [Compiler options](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compilers-compiler-options)) are used to specify the output file type.

| File type | Default filename | Input files |
| --- | --- | --- |
| Executable file | `a.out` | The specified source files are compiled and linked to a single executable file. |
| Object file | `file.o` | Each specified source file is compiled to a separate object file (where file is the source filename). |
| Assembly source file | `file.s` | Each specified source file is compiled to a separate assembly source file (where file is the source filename). |
| Preprocessed C/C++ source file | `stdout` | The preprocessor output is written to the standard output. |

## Compiler options

The LLVM compilers can be controlled by command-line options (see [Start the compilers](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compilers-start)). Many of the GCC options are supported, along with options that are LLVM-specific.

Many of the `-f`, `-m`, and `-W` options can be written in two ways: `-f<option>` to enable a binary option, or `-fno-<option>` to disable the option.

`-mllvm` is not a standalone option, but rather a standard prefix that appears in many LLVM- specific option names.

Following is a quick reference of the options.

[Display](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-display-sub)

-help
    -v
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[Compilation](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-compilation-sub)

-###
    -c
    -cc1
    -ccc-print-phases
    -E
    -pipe
    -o <file>
    -S
    -Wa,<arg>[,<arg...>]
    -Wl,<arg>[,<arg...>]
    -Wp,<arg>[,<arg...>]
    -x <language>
    -Xclang <arg>
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[C dialect](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-c-dialect-sub)

-ansi
    -fblocks
    -fgnu-runtime
    -fgnu89-inline
    -fno-asm
    -fsigned-bitfields
    -fsigned-char
    -funsigned-char
    -no-integrated-cpp
    -std=(c89|gnu89|c99|gnu99|c11|gnu11)
    -traditional
    -Wpointer-sign
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[C++ dialect](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-cpp-dialect-sub)

-cxx-isystem <dir>
    -ffor-scope  |  -fno-for-scope
    -fno-gnu-keywords
    -ftemplate-depth-n
    -fvisibility-inlines-hidden
    -fuse-cxa-atexit
    -nobuiltininc
    -nostdinc++
    -std=(c++98|gnu++98|c++11|gnu++11|c++14|gnu++14|c++17|gnu++17)
    -Wc++0x-compat
    -Wno-deprecated
    -Wnon-virtual-dtor
    -Woverloaded-virtual
    -Wreorder
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[Warning and error messages](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-warn-err-msgs-sub)

c++98|c++11|c++14|c++17-compat-pedantic
    cast-calling-convention
    -ccc-print-diag-group name | -ccc-print-diag-group-verbose name
    comma
    constant-conversion
    expansion-to-defined
    -ferror-limit=<n>
    -ferror-warn <filename>
    float-overflow-conversion
    float-zero-conversion
    -fscanban-file <file>
    -ftemplate-backtrace-limit=<n>
    -fsyntax-only
    incompatible-sysroot
    nonportable-include-path
    nonportable-system-include-path
    null-dereference
    openmp-target
    -pedantic  |  -Wpedantic
    pedantic-core-features
    -pedantic-errors
    -Qunused-arguments
    shadow-field-in-constructor-modified
    shadow-field-in-constructor
    undefined-func-template
    undefined-var-template
    unguarded-availability
    unknown-argument
    unsupported-cb
    varargs
    -w
    -W<foo>
    -Wno-<foo>
    -Wall
    -Warray-bounds
    -Wcast-align
    -Wchar-subscripts
    -Wcomment
    -Wconversion
    -Wdeclaration-after-statement
    -Wno-deprecated-declarations
    -Wempty-body
    -Wendif-labels
    -Werror
    -Werror=foo
    -Wno-error=foo
    -Werror-implicit-function-declaration
    -Weverything
    -Wextra
    -Wfloat-equal
    -Wformat
    -Wformat=2
    -Wformat-nonliteral
    -Wformat-security
    -Wignored-qualifiers
    -Wimplicit
    -Wimplicit-function-declaration
    -Wimplicit-int
    -Wno-format-extra-args
    -Wno-invalid-offsetof
    -Wlong-long
    -Wmain
    -Wmissing-braces
    -Wmissing-declarations
    -Wmissing-noreturn
    -Wmissing-prototypes
    -Wno-multichar
    -Wnonnull
    -Wpacked
    -Wpadded
    -Wparentheses
    -Wpedantic
    -Wpointer-arith
    -Wreturn-type
    -Wscanban
    -Wshadow
    -Wsign-compare
    -Wswitch  |  -Wswitch-enum
    -Wsystem-headers
    -Wtautological-constant-out-of-range-compare
    -Wtrigraphs
    -Wundef
    -Wuninitialized
    -Wunknown-pragmas
    -Wunreachable-code
    -Wunused
    -Wunused-function
    -Wunused-label
    -Wunused-parameter
    -Wunused-value
    -Wunused-variable
    -Wwrite-strings
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[Debugging](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-debug-sub)

-dumpmachine
    -dumpversion
    -feliminate-unused-debug-symbols
    -ftime-report  |  -time
    -g[<level>]
    -gline-tables-only
    --print-diagnostic-categories
    -print-file-name=library
    -print-libgcc-file-name
    -print-multi-directory
    -print-multi-lib
    -print-multi-os-directory
    -print-prog-name=program
    -print-search-dirs
    -save-temps
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[Diagnostic format](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-diag-format-sub)

-fcaret-diagnostics        |  -fno-caret-diagnostics
    -fdiagnostics-show-option  |  -fno-diagnostics-show-option
    -fdiagnostics-show-category=(none|id|name)
    -fdiagnostics-print-source-range-info
    -fdiagnostics-parseable-fixits
    -fdiagnostics-show-template-tree
    -fmessage-length=<n>
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[Individual warning groups](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-ind-warn-groups-sub)

-Wextra-tokens
    -Wambiguous-member-template
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[Compiler crash diagnostics](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-crash-diag-sub)

-fno-crash-diagnostics
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[Preprocessor](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-preprocessor-sub)

-A pred=<ans>
    -A -pred=<ans>
    -ansi
    -C
    -CC
    -d(DMNU)
    -D <name>  |  -D <name>=<definition>
    -fexec-charset=charset
    -finput-charset=charset
    -fstrict-overflow
    -ftabstop=<width>
    -H
    --help
    -I <dir>
    -I-
    -include <file>
    -isystem <prefix>
    --system-header-prefix=<prefix>
    --no-system-header-prefix=<prefix>
    -M
    -MD
    -MF <file>
    -MG
    -MM
    -MMD
    -MP
    -MQ <target>
    -MT <target>
    -nostdinc
    -nostdinc++
    -o <file>
    -P
    -remap
    --target-help
    -traditional-cpp
    -trigraphs
    -U name
    -v
    -version
    --version
    -w
    -Wall
    -Wcomment  |  -Wcomments
    -Wendif-labels
    -Werror
    -Wimport
    -Wsystem-headers
    -Wtrigraphs
    -Wundef
    -Wunused-macros
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[Assembling](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-assembling-sub)

-fintegrated-as
    -fno-integrated-as
    -Xassembler <arg>
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[Linking](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-linking-sub)

object_file_name
    -c
    -dynamic
    -E
    -l <library>
    -moslib=<library>
    -nodefaultlibs
    -nostartfiles
    -nostdlib
    -pie
    -s
    -S
    -shared
    -shared-libgcc
    -static
    -static-libgcc
    -u symbol
    -Xlinker arg
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[Processor version](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-processor-version-sub)

-mv68  | -mv69 | -mv71 | -mv71t | -mv73 | -mv75 | -mv79 | -mv81 | -mv83 | -mv85 | -mv89 | -mv91
    -mhvx
    -mhvx=version
    -mno-hvx
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[Code generation](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-code-gen-sub)

-femit-all-decls
    -ffixed-r<nn>
    -fmerge-functions  |  -fno-merge-functions
    -fno-exceptions
    -fpic
    -fPIC
    -fpie  |  -fPIE
    -fshort-enums  |  -fno-short-enums
    -fshort-wchar  |  -fno-short-wchar
    -ftrap-function=<name>
    -ftrapv
    -ftrapv-handler=<name>
    -funwind-tables
    -fverbose-asm
    -fvisibility=[default|internal|hidden|protected]
    -fwrapv
    -G size
    -mno-global-merge
    -mno-packets
    -mlong-calls
    -mhvx-length=[64B,128B]
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[Optimization](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-optimization-sub)

-O0
    -O  |  -O1
    -O2
    -O3
    -Os
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[Specific optimizations](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-specific-optimizations-sub)

-fdata-sections
    -ffast-math
    -ffp-contract=[off|on|fast]
    -ffunction-sections
    -finline
    -finline-functions
    -fno-zero-initialized-in-bss
    -fno-merge-all-constants
    -fomit-frame-pointer
    -foptimize-sibling-calls
    -fstack-protector
    -fstack-protector-all
    - fstack-protector-strong
    -fstrict-aliasing
    -funit-at-a-time
    -funroll-all-loops
    -funroll-loops
    -fvectorize
    --param ssp-buffer-size=<size>
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[Link-time optimization](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-link-time-optimization-sub) (compiler and linker)

-flto  |  -flto=thin
    -flto-options=<>
    -flto-options=codegen="<list of options>"
    -flto-options=cache=<path>
    -flto-options=nooptimal-preservelist
    -flto-options=preserveall
    -flto-options=preserve-file=<file>
    -flto-options=preserve-sym=<symbol>
    -flto-options=save-lto-output-file=<filename>
    -flto-options=threads=<n>
    -flto-use-as
    -save-temps
    -trace=lto
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[Compiler security](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-compiler-security-sub)

--analyze
    -analyzer-checker=<checker>
    -analyzer-checker-help
    -analyzer-disable-checker=<checker>
    -Xclang -analyzer-output html
    -Xclang -analyzer-werror
    --compile-and-analyze <dir>
    --compile-and-analyze-high
    --compile-and-analyze-medium
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### Display

-help
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Display compiler command and option summary.

-v
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Display compiler release version.

### Compilation

-###
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Print commands used to perform the compilation.

-c
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Compile the source file, but does not link it.

-cc1
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Bypass the compiler driver and goes directly to the LLVM compiler.

-ccc-print-phases
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Print the compilation stages as they occur.

-E
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Preprocess the source file only; does not compile it.

-pipe
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Communicate between compiler stages using pipes not temporary files.

-o <file>
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Specify the name of the compiler output file.

-S
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Compile the source file, but does not assemble it.

-Wa,<arg>[,<arg>...]
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Pass the specified arguments to the assembler.

-Wl,<arg>[,<arg>...]
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Pass the specified arguments to the linker.

-Wp,<arg>[,<arg>...]
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Pass the specified arguments to the preprocessor.

-x <language>
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Specify the language of the subsequent source files specified on the command line.

-Xclang <arg>
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Pass the specified argument to the compiler.

### C dialect

-ansi
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For C, support ISO C90.

For C++, remove conflicting GNU extensions.

-fblocks
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Enable the Apple blocks extension.

-fgnu-runtime
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Generate output compatible with the standard GNU Objective-C runtime.

-fgnu89-inline
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Use the gnu89 inline semantics.

-fno-asm
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Do not recognize asm, inline, or typeof as keywords.

-fsigned-bitfields
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Define bit fields as signed.

-fsigned-char
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Define the char type as signed.

-funsigned-char
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Define the char type as unsigned.

-no-integrated-cpp
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Compile using separate preprocessing and compilation stages.

-std=(c89|gnu89|c99|gnu99|c11|gnu11)
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LLVM C language mode. The default setting is gnu11.

-traditional
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Support pre-standard C language.

-Wpointer-sign
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Flag pointers when they are assigned, or passed values with differing signs.

### C++ dialect

-cxx-isystem <dir>
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Add a specified directory to C++ SYSTEM include search path.

-ffor-scope
    -fno-for-scope
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Control whether the scope of a variable declared in a for statement is limited to the statement or to the scope enclosing the statement.

-fno-gnu-keywords
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Disable recognizing typeof as a keyword.

-ftemplate-depth-n
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Specify the maximum instantiation depth of a template class.

-fvisibility-inlines-hidden
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Specify the default visibility for inline C++ member functions.

-fuse-cxa-atexit
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Register destructors with function cxa\_atexit (instead of atexit). This option applies only to objects that have static storage duration.

-nobuiltininc
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Disable built-in #include directories.

-nostdinc++
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Disable standard #include directories for the C++ standard library.

-std=(c++98|gnu++98|c++11|gnu++11|c++14|gnu++14|c++17|gnu++17)
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LLVM C++ language mode. The default setting is gnu++14.

-Wc++0x-compat
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Generate warnings for C++ constructs with different semantics in ISO C++ 1998 and ISO C++ 200x.

-Wno-deprecated
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Do not generate warnings when deprecated features are used.

-Wnon-virtual-dtor
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Generate a warning when a polymorphic class is declared with a non-virtual destructor.

-Woverloaded-virtual
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Generate a warning when a function hides virtual functions from a base class.

-Wreorder
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Generate a warning when member initializers do not appear in the code in the required execution order.

### Warning and error messages

c++98|c++11|c++14|c++17-compat-pedantic
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Warn if the compiled code uses experimental features added to language standards more recent than C++17.

cast-calling-convention
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Cast between incompatible %0 and %1 calling conventions. Calls through this pointer might abort at runtime.

-ccc-print-diag-group <name>
    -ccc-print-diag-group-verbose <name>
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Display the diagnostics assigned to the diagnostic group `<name>`. These options are used with `-W<group>` to control sets of diagnostics.

comma
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Possible misuse of comma operator here.

constant-conversion
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Implicit conversion from %2 to %3 changes the value from %0 to %1.

expansion-to-defined
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Macro expansion producing defined has undefined behavior.

-ferror-limit=<>n>
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Stop emitting diagnostics after `<n>` errors have been produced. The default setting is 20.

Disable the error limit with `-ferror-limit=0`.

-ferror-warn <filename>
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Convert the specified set of compiler warnings into errors.

The specified text file contains a list of warning names, with each warning name separated by whitespace in the file.

Warning names are based on the switch names of the corresponding compiler warning message options. For example, to convert the warnings generated by `-Wunused-variable`, use the warning name, `unused-variable`.

You can specify this option multiple times.

Note

You can integrate this option (and its associated file) into a build system and use it to iteratively resolve the warning messages generated by a project.

float-overflow-conversion
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Implicit conversion of out of range value from %0 to %1 changes the value from %2 to %3.

float-zero-conversion
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Implicit conversion from %0 to %1 changes the non-zero value from %2 to %3.

-fscanban-file <file>
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Include functions listed in the text file into the banned functions list. The entries in the additional banned functions file are to be
added on a line-by-line basis in the following format:

> 
> 
> <banned function name>,<alternative function to be used in its place>
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An alternative must be added when banning a function.

-ftemplate-backtrace-limit=<n>
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Only emit up to &lt;n&gt; template instantiation notes within the template instantiation backtrace for a single warning or error. The default setting is 10.

Disable the limit with `-ftemplate-backtrace-limit=0`.

-fsyntax-only
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Check for syntax errors only.

incompatible-sysroot
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Use sysroot for %0 but targets %1.

nonportable-include-path
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Non-portable path to file %0. The specified path differs in case from the filename on the disk.

nonportable-system-include-path
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Non-portable path to file %0. The specified path differs in case from the filename on the disk.

null-dereference
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Binding a dereferenced NULL pointer to a reference has undefined behavior.

openmp-target
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Declaration is not declared in any declare target region.

-pedantic
    -Wpedantic
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Generate all warnings required by the ISO C and ISO C++ standards.

pedantic-core-features
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OpenCL extension %0 is a core feature or a supported optional core feature; ignored.

-pedantic-errors
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Equivalent to `-pedantic`, but generate errors instead of warnings.

-Qunused-arguments
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Do not generate warnings for unused driver arguments.

shadow-field-in-constructor-modified
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Modify constructor parameter %0 that shadows a field of %1.

shadow-field-in-constructor
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Constructor parameter %0 shadows field %1 of %2.

undefined-func-template
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Instantiation of function %q0 is required, but no definition is available.

undefined-var-template
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Instantiation of variable %q0 is required, but no definition is available.

unguarded-availability
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Use `*` case; platform %0 is not accounted for.

unknown-argument
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Ignore an unknown argument in clang-cl: %0.

unsupported-cb
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Ignore the -mcompact-branches= option because the %0 architecture does not support it.

varargs
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Passing an object that undergoes a default argument promotion to `va_start` has undefined behavior.

-w
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Suppress all warnings.

-W<foo>
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Enable the diagnostic (or diagnostic group) `<foo>`.

-Wno-<foo>
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Disable the diagnostic (or diagnostic group) `<foo>`.

-Wall
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Enable all `-W` options.

-Warray-bounds
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Generate a warning if array subscripts are out of bounds.

-Wcast-align
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Generate a warning if a pointer cast increases the required alignment of the target.

-Wchar-subscripts
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Generate a warning if array subscript is type char.

-Wcomment
    
      Generate a warning if a comment symbol appears inside a comment.
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-Wconversion
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Generate a warning if an implicit conversion might alter a value.

-Wdeclaration-after-statement
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Generate a warning when a declaration appears in a block after a statement.

-Wno-deprecated-declarations
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Do not generate warnings for functions, variables, or types assigned the attribute `deprecated`.

-Wempty-body
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Generate a warning if an `if`, `else`, or `do while` statement contains an empty body.

**-Wendif-labels**
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Generate a warning if an `#else` or `#endif` directive is followed by text.

-Werror
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Convert all warnings into errors.

-Werror=<foo>
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Convert the diagnostic (or diagnostic group) `<foo>` into an error.

-Wno-error=<foo>
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Keep the diagnostic (or diagnostic group) `<foo>` as a warning, even if `-Werror` is used.

-Werror-implicit-function-declaration
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Generate a warning or error if a function is used before being declared.

-Weverything
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Enable all warnings.

-Wextra
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Enable selected warning options, and generate warnings for selected events.

-Wfloat-equal
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Generate a warning if two floating-point values are compared for equality.

-Wformat
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In calls to `printf`, `scanf`, and other functions with format strings, ensure that the arguments are compatible with the specified format string.

-Wformat=2
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Equivalent to specifying the following options: `-Wformat -Wformat-nonliteral -Wformat-security -Wformat-y2k`.

-Wformat-nonliteral
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Generate a warning if the format string is not a string literal, except if the format arguments are passed through `va_list`.

-Wformat-security
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Generate a warning for format function calls that might cause security risks.

-Wignored-qualifiers
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Generate a warning if a return type has a qualifier (such as `const`).

-Wimplicit
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Equivalent to `-Wimplicit-int` and `-Wimplicit-function-declaration`.

-Wimplicit-function-declaration
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Generate a warning if a function is used before it is declared.

-Wimplicit-int
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Generate a warning if a declaration does not specify a type.

-Wno-format-extra-args
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Do not generate a warning for passing extra arguments to `printf` or `scanf`.

-Wno-invalid-offsetof
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Do not generate a warning if a non-POD type is passed to the `offsetof` macro.

-Wlong-long
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Generate a warning if typelong long is used.

-Wmain
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Generate a warning if the `main()` function has any suspicious properties.

-Wmissing-braces
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Generate a warning if an aggregate or union initializer is not properly bracketed.

-Wmissing-declarations
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Generate a warning if a global function is defined without being first declared.

-Wmissing-noreturn
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Generate a warning if a function does not include a return statement.

-Wmissing-prototypes
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Generate a warning if a global function is defined without a prototype.

-Wno-multichar
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Do not generate a warning if a multiple-character constant is used.

-Wnonnull
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Generate a warning if a NULL pointer is passed to an argument that is specified to require a non-NULL value (with the `nonnull` attribute).

-Wpacked
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Generate a warning if the memory layout of a structure is not affected after the structure is specified with the `packed` attribute.

-Wpadded
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Generate a warning if the memory layout of a structure includes padding.

-Wparentheses
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Generate a warning if the parentheses are omitted in certain cases.

-Wpedantic
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See `-pedantic`.

-Wpointer-arith
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Generate a warning if any code depends on the size of `void` or a function type.

-Wreturn-type
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Generate a warning if a function returns a type that defaults to `int`, or a value is incompatible with the defined return type.

-Wscanban
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Generate a warning if a banned function is being used.

The default list of banned functions adheres to the `QC-ScanBan` list. Use the `-fscanban-file` flag to add more banned functions.

-Wshadow
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Generate a warning if a local variable shadows another local variable, global variable, or parameter; or if a built-in function gets shadowed.

-Wsign-compare
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Generate a warning in a signed/unsigned compare operation if the result might be inaccurate due to the signed operand being converted to unsigned.

-Wswitch
    -Wswitch-enum
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Generate a warning if a `switch` statement uses an `enum` type for the index, and does not specify a `case` for every possible enumeration value, or specifies a `case` with a value outside the enumeration range.

-Wsystem-headers
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Generate a warning for constructs declared in system header files.

-Wtautological-constant-out-of-range-compare
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Generate a warning if a compare is performed using an operand type, which by definition always yields a `TRUE` (or `FALSE`) compare result. For example, `i >= 0`, where `i` is an unsigned integer type.

-Wtrigraphs
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Generate a warning if a trigraph forms an escaped newline in a comment.

-Wundef
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Generate a warning if an undefined non-macro identifier appears in `#if` directive.

-Wuninitialized
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Generate a warning if referencing an uninitialized automatic variable.

-Wunknown-pragmas
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Generate a warning if a `#pragma` directive is not recognized by the compiler.

-Wunreachable-code
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Generate a warning if code will never be executed.

-Wunused
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Specify all the `-Wunused` options.

-Wunused-function
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Generate a warning if a static function is declared without being defined or used.

Note

No warning is generated for functions declared or defined in header files.

-Wunused-label
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Generate a warning if a label is declared without being used.

-Wunused-parameter
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Generate a warning if a function argument is not used in its function.

-Wunused-value
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Generate a warning if the value of a statement is not subsequently used.

-Wunused-variable
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Generate a warning if a local or non-constant static variable is not used in its function.

-Wwrite-strings
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For C, assign string constants the type `const char[<length>]` to ensure that a warning is generated if the string address gets copied to a non `const char *` pointer.

For C++, generate a warning that states a string constant is being converted to `char *`.

### Debugging

-dumpmachine
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Display the target machine name.

-dumpversion
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Display the compiler version.

-feliminate-unused-debug-symbols
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Generate debug information only for the symbols that are used. (Debug information is generated in STABS format.)

-ftime-report
    -time
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Display the elapsed time for each stage of the compilation.

-g[<level>]
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Generate complete source-level debug information.

-gline-tables-only
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Generate source-level debug information with line number tables only.

--print-diagnostic-categories
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Display mapping of diagnostic category names to category identifiers.

-print-file-name=<library>
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Display the full library path of the specified file.

-print-libgcc-file-name
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Display the library path for the `libgcc.a` file.

-print-multi-directory
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Display the directory names of the multiple libraries specified by other compiler options in the current compilation.

-print-multi-lib
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Display the directory names of the multiple libraries paired with the compiler options that specified the libraries in the current compilation.

-print-multi-os-directory
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Display the relative path that is appended to the multi-lib search paths.

-print-prog-name=<program>
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Display the absolute path of the specified program.

-print-search-dirs
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Display the search paths used to locate libraries and programs during compilation.

-save-temps
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Save the normally-temporary intermediate files generated during compilation.

### Diagnostic format

By default, the LLVM compiler aims to produce beautiful diagnostics, especially for new users just beginning to use these compilers. However, different users have different preferences, and sometimes an LLVM compiler is driven by another program that requires the diagnostic output to be simple and consistent rather than user-friendly. For these cases, the LLVM compilers provide a wide range of options to control the output format of the diagnostics that it generates.

-fcaret-diagnostics
    -fno-caret-diagnostics
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Print source line and ranges from source code in diagnostic format.

This option controls whether the LLVM compiler prints the source line, source ranges, and caret when emitting a diagnostic. The default setting is `enabled`. When enabled, the LLVM compiler prints information like the following example:

> 
> 
> test.c:28:8: warning: extra tokens at end of #endif directive
>     [-Wextra-tokens]
>     #endif bad
>            ^
>            //
>     -fdiagnostics-format=(clang|msvc|vi)
>     Copy to clipboard

This option changes the diagnostic output format to better match IDEs and command line tools. It controls the output format of the filename, line number, and column printed in diagnostic messages. The default setting is `clang`. The effect of the setting the output format is shown in the following examples.

- `clang`

> 
> 
> t.c:3:11: warning: conversion specifies type 'char *' but the argument has type `int`
>         Copy to clipboard
- `msvc`

> 
> 
> t.c(3,11) : warning: conversion specifies type 'char *' but the argument has type `int`
>         Copy to clipboard
- `vi`

> 
> 
> t.c +3:11: warning: conversion specifies type 'char *' but the argument has type `int`
>         Copy to clipboard

-fdiagnostics-show-option
    -fno-diagnostics-show-option
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Enable `[-W<option>]` information in diagnostic line.

This option controls whether the LLVM compiler prints the associated warning group option name (see [Diagnostic categories](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-ctrl-diag-msgs-diag-categories-sub)) when outputting a warning diagnostic. The default setting is `disabled`.0000

For example, given the following diagnostic output:

> 
> 
> test.c:28:8: warning: extra tokens at end of #endif directive
>     [-Wextra-tokens]
>     #endif bad
>            ^
>            //
>     Copy to clipboard

In this case, specifying `-fno-diagnostics-show-option` prevents the LLVM compiler from printing the `[-Wextra-tokens]` information in the diagnostic output. This information indicates the option that is required to enable or disable the diagnostic, either from the command line or by using the `GCC diagnostic` pragma (see [Control diagnostics with pragmas](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-ctrl-diag-msgs-diag-pragmas-sub)).

-fdiagnostics-show-category=(none|id|name)
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Enable printing category information in diagnostic line.

This option controls whether the LLVM compiler prints the category associated with a diagnostic when emitting it. The default setting is `none`. The effect of the setting the output format is shown in the following examples.

- `none`

> 
> 
> t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat]
>         Copy to clipboard
- `id`

> 
> 
> t.c:3:11: warning: conversion specifies type 'char *' but the  argument has type 'int' [-Wformat,1]
>         Copy to clipboard
- `name`

> 
> 
> t.c:3:11: warning: conversion specifies type 'char *' but the argument has type 'int' [-Wformat,Format String]
>         Copy to clipboard

Each diagnostic can have an associated category. If it has one, it is listed in the diagnostic category field of the diagnostic line (in the `[]` brackets).

This option can be used to group diagnostics by category, so it should be a high-level category; the goal is to have dozens of categories, not hundreds or thousands of them.

-fdiagnostics-print-source-range-info
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Print machine-parseable information about source ranges.

This option controls whether the LLVM compiler prints information about source ranges in a machine-parseable format after the file/line/column number information. The default setting is disabled. Omit this option to supress the information. The information is a simple sequence of brace- enclosed ranges, where each range lists the start and end line/column locations.

For example, given the following output:

> 
> 
> exprs.c:47:15:{47:8-47:14}{47:17-47:24}: error: invalid operands to binary expression ('int *' and '_Complex float')
>     P = (P-42) + Gamma*4;
>         ~~~~~~ ^ ~~~~~~~
>     Copy to clipboard

In this case, `-fdiagnostics-print-source-range-info` generates the braces, `{}`.

The printed column numbers count bytes from the beginning of the line; take care if the source contains multiple-byte characters.

-fdiagnostics-parseable-fixits
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Print Fix-Its in a machine-parseable format.

This option makes the LLVM compiler print available Fix-Its in a machine-parseable format at the end of diagnostics. The following example illustrates the format:

> 
> 
> fix-it:"t.cpp":{7:25-7:29}:"Gamma"
>     Copy to clipboard

In this case, the range printed is half-open, so the characters from column 25 up to (but not including) column 29 on line 7 of file `t.cpp` should be replaced with the string `Gamma`. Either the range or replacement string can be empty (representing strict insertions and strict erasures, respectively). Both the filename and insertion string escape backslash (as `\\`), tabs (as `\t`), newlines (as `\n`), double quotes (as `\"`), and non-printable characters (as octal `\xxx`).

The printed column numbers count bytes from the beginning of the line; take care if the source contains multiple-byte characters.

-fdiagnostics-show-template-tree
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For large templated types, cause the LLVM compiler to display the templates as an indented text tree, with one argument per line, and any differences marked inline.

- `default`

> 
> 
> t.cc:4:5: note: candidate function not viable: no known conversion from 'vector<map<[...], map<float, [...]>>>' to 'vector<map<[...], map<double, [...]>>>' for 1st argument;
>         Copy to clipboard
- `-fdiagnostics-show-template-tree`

> 
> 
> t.cc:4:5: note: candidate function not viable: no known conversion for 1st argument;
>           vector<
>             map<
>               [...],
>               map<
>                 [float != float],
>                 [...]>>>
>         Copy to clipboard

-fmessage-length=<n>
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Format error messages to fit on lines with the specified number of characters.

### Individual warning groups

-Wextra-tokens
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Warn about excess tokens at the end of a preprocessor directive.

This option enables warnings about extra tokens at the end of preprocessor directives. The default setting is enabled. For example:

> 
> 
> test.c:28:8: warning: extra tokens at end of #endif directive
>     [-Wextra-tokens]
>     #endif bad
>            ^
>     Copy to clipboard

These extra tokens are not strictly conforming and are usually best handled by commenting them out.

-Wambiguous-member-template
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Warn about unqualified uses of a member template whose name resolves to another template at the location of the use.

This option (which is enabled by default) generates a warning in the following code:

> 
> 
> template<typename T> struct set{};
>     template<typename T> struct trait { typedef const T& type; }; struct Value {
>       template<typename T> void set(typename trait<T>::type value){}
>     };
>     void foo() {
>       Value v;
>       v.set<double>(3.2);
>     }
>     Copy to clipboard

C++ requires this to be an error, but because it is difficult to work around, the LLVM compiler downgrades it to a warning as an extension.

### Compiler crash diagnostics

The LLVM compiler might crash once in a while. Typically, a crash occurs only when using the latest version of the compiler.

The LLVM compiler goes to great lengths to provide assistance in filing a bug report. Specifically, after a crash, it generates preprocessed source files and associated run scripts. Attach these files to a bug report to ease reproducibility of the failure. The following compiler option is used to control the crash diagnostics.

-fno-crash-diagnostics
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Disable auto-generation of preprocessed source files during an LLVM crash.

This option can be helpful for speeding up the process of generating a delta reduced test case.

### Preprocessor

-A pred=<ans>
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Assert the predicate `pred` and answer `ans`.

-A -pred=<ans>
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Cancel the specified assertion.

-ansi
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Use the C89 standard.

-C
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Retain comments during preprocessing.

-CC
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Retain comments during preprocessing, including during macro expansion.

-d(DMNU)
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Print macro definitions or names based on the following arguments:

- `D` - Print macro definitions in `-E` mode in addition to normal output.
- `M` - Print macro definitions in `-E` mode instead of normal output.
- `N` - Print macro names in `-E` mode in addition to normal output.
- `U` - Print referenced macro definitions in `-E` mode in addition to normal output. It also prints #undefs for macros that are undefined when referenced. Both are printed at the point they are referenced.

-D <name>
    -D <name>=<definition>
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Define the specified macro symbol.

-fexec-charset=charset
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Specify the character set used to encode strings and character constants. The default character set is UTF-8.

-finput-charset=charset
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Specify the character set used to encode the input files. The default setting is UTF-8.

-fstrict-overflow
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Enforce strict language semantics for pointer arithmetic and signed overflow.

-ftabstop=<width>
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Specify the tab stop distance.

-H
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Display the header includes and nesting depth.

--help
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Display the preprocessor release version.

-I <dir>
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Add the specified directory to the list of search directories for header files.

-I-
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Deprecated.

-include <file>
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Include the contents of the specified source file.

-isystem <prefix>
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Treat an included file as a system header if it is found on the specified path (see [Control diagnostics in system headers](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-ctrl-diag-msgs-diag-sys-headers-sub)).

Copy to clipboard

Treat an included file as a system header if it is found on the specified sub-path of a defined include path (see [Control diagnostics in system headers](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-ctrl-diag-msgs-diag-sys-headers-sub)).

Copy to clipboard

Do not treat an included file as a system header if it is found on the specified sub- path of a defined include path (see [Control diagnostics in system headers](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-ctrl-diag-msgs-diag-sys-headers-sub)).

-M
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Output a make rule describing the dependencies of the main source file.

-MD
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Equivalent to `-M -MF <file>`, except `-E` is not implied.

-MF <file>
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Write dependencies to the specified file.

-MG
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Add missing headers to the dependency list.

-MM
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Equivalent to `-M`, except this option does not mention header files found in the system header directories.

-MMD
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Equivalent to `-MD`, except this option mentions only user header files, not system header files.

-MP
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Create artificial target for each dependency.

-MQ <target>
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Specify a target to quote for dependency.

-MT <target>
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Specify target for dependency.

-nostdinc
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Omit searching for header files in the standard system directories.

-nostdinc++
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Omit searching for header files in the C++-specific standard directories.

-o <file>
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Specify the name of the preprocessor output file.

-P
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Disable line marker output when using `-E`.

-remap
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Generate code for file systems that only support short filenames.

--target-help
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Display all command options and exit immediately.

-traditional-cpp
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Emulate pre-standard C preprocessors.

-trigraphs
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Preprocess trigraphs.

-U <name>
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Cancel any previous definition of the specified macro symbol.

-v
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Equivalent to -help.

-version
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Display the preprocessor version during preprocessing.

--version
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Display the preprocessor version and exit immediately.

-w
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Suppress all preprocessor warnings.

-Wall
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Enable all warnings.

-Wcomment
    -Wcomments
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Generate a warning if a comment symbol appears inside a comment.

-Wendif-labels
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Generate a warning if an `#else` or `#endif` directive is followed by text.

-Werror
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Convert all warnings into errors.

-Wimport
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Generate a warning when `#import` is used the first time.

-Wsystem-headers
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Generate a warning for constructs declared in system header files.

-Wtrigraphs
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Generate a warning if a trigraph forms an escaped newline in a comment.

-Wundef
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Generate a warning if an undefined non-macro identifier appears in an `#if` directive.

-Wunused-macros
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Generate a warning if a macro is defined without being used.

### Assembling

-fintegrated-as
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Enable the integrated assembler.

-fno-integrated-as
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Disable the integrated assembler.

Note

The `-Wa` switches (see [Compilation](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-compilation-sub)) are accepted only if the integrated assembler is disabled with `-fno-integrated-as`.

-Xassembler <arg>
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Pass the specified argument to the assembler.

### Linking

object_file_name
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Linker input file.

-c
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Do not perform linking. This option is used with spec strings.

-dynamic
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Link with a shared library (instead of a static library).

-E
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Do not perform linking. This option is used with spec strings.

-l <library>
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Search the specified library file while linking.

-moslib=<library>
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Search the RTOS-specific library named `liblibrary.a`. The search paths for the library and include files must be explicitly specified.

-nodefaultlibs
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Do not use the standard system libraries when linking.

-nostartfiles
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Do not use the standard system startup files when linking.

-nostdlib
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Do not use the standard system startup files or libraries when linking.

-pie
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Generate a position-independent executable as the output file.

-s
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Delete all symbol table information and relocation information from the executable.

-S
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Do not perform linking. This option is used with spec strings.

-shared
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Generate a shared object as the output file. The resulting file can be subsequently linked with other object files to create an executable.

-shared-libgcc
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Link with the shared version of the `libgcc` library.

**-static**
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Do not link with the shared libraries. Only relevant when using dynamic libraries.

-static-libgcc
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Link with the static version of the `libgcc` library.

-u <symbol>
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Pretend the `symbol` is undefined to force linking of library modules to define `symbol`.

-Xlinker <arg>
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Pass the specified argument to the linker.

### Directory search

-B<prefix>
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Specify the top-level directory of the compiler.

-F <dir>
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Add the specified directory to the search path for framework includes.

-I <dir>
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Add the specified directory to the include file search path.

-I-
    Copy to clipboard

Deprecated.

L<dir>
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Add the specified directory to the list of directories searched by the `-l` option.

### Processor version

-mv68
    -mv69
    -mv71
    -mv71t
    -mv73
    -mv75
    -mv79
    -mv81
    -mv83
    -mv85
    -mv89
    -mv91
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Specify the Hexagon processor version for which the compiler will generate code. For more information on the processor versions, see the *Qualcomm Hexagon Programmer’s Reference Manual* (see [References](https://docs.qualcomm.com/doc/80-N3040-23/topic/references.html)).

Note

Not all `-mvX` options are supported in all Hexagon tools releases. The default option setting is also release-specific. For more information, see [Processor versions](https://docs.qualcomm.com/doc/80-N3040-23/topic/functional-overview.html#hccpp-functional-overview-proc-vers).

-mhvx
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Enable HVX. The default Hexagon HVX coprocessor version is the Hexagon processor version. If no `-mhvx-length` flag is specified, the default vector length is 128 bytes for all processor versions supported by Hexagon Clang 23.0.

- For V68 and later, the default vector length is 128 bytes.

-mhvx=version
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Specify the Hexagon HVX coprocessor version (V68, V69, V73, V75, V79, V81, V85, V89, V91) for which the compiler will generate code.

If no `-mhvx-length` flag is specified, the default vector length is 128 bytes for all processor versions supported by Hexagon Clang 23.0.

- For V68 and later, the default vector length is 128 bytes.

-mno-hvx
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Disable HVX.

### Code generation

-fasynchronous-unwind-tables
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Generate an unwind table. The table is stored in DWARF2 format.

-femit-all-decls
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Emit all declarations, even if unused.

-ffixed-r<nn>
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Reserve the `rnn` register. The compiler does not use this register in code that it generates.

-fmerge-functions
    -fno-merge-functions
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Merge functions that are equivalent or that differ by only a few instructions (see [Merge functions](https://docs.qualcomm.com/doc/80-N3040-23/topic/code-optimization.html#hccpp-code-optimize-merge-function)). The default setting is disabled.

This option attempts to improve code size by merging similar functions. It uses a number of heuristics to determine whether it is worthwhile to merge a pair of functions. For instance, very small functions or functions with significant differences are usually not merged.

Note

Because this option might have a negative impact on program performance, it is disabled by default. It becomes enabled only when it is specified explicitly.

-fno-exceptions
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Do not generate code for propagating exceptions.

-fpic
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Generate position-independent code (PIC) for use in a shared library.

-fPIC
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Generate position-independent code for dynamic linking, avoiding any limits on the size of the global offset table.

-fpie
    -fPIE
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Generate position-independent code (PIC) for linking into executables.

-fshort-enums
    -fno-short-enums
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Allocate to an enum type only as many bytes necessary for the declared range of possible values. The default setting is `disabled`.

-fshort-wchar
    -fno-short-wchar
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Force wchar\_t to be short unsigned int. The default setting is `disabled`.

-ftrap-function=<name>
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Issue a call to the specified function rather than a trap instruction.

-ftrapv
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Trap on an integer overflow.

-ftrapv-handler=<name>
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Specify the function to be called in the case of an overflow.

-funwind-tables
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Similar to -fexceptions, except this option only generates any necessary static data without affecting the generated code in any other way.

-fverbose-asm
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Add commentary information to the generated assembly code to improve code readability.

-fvisibility=[default|internal|hidden|protected]
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Set the default symbol visibility for all global declarations.

-fwrapv
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Treat a signed integer overflow as two’s complement.

-G <size>
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Assign data objects that fit within the specified size to the `.sdata` / `.sbss` section. The size is in bytes, and the default value is 8.

Compiling with `-G 0` requires all other files in the application to be compiled with `-G 0`.

An application must be compiled with a `-G` value that is no larger than the smallest `-G` value that any of its libraries was compiled with.

-mno-global-merge
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Disable merging of globals.

-mno-packets
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Do not generate packets. This option is supported for optimization levels -O1 and - O2.

-mlong-calls
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Generate long calls.

-mhvx-length=[64B,128B]
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Set the vector length to the value provided and overrides the default value set by `-mhvx` or `-mhvx=flags`.

This option is valid only for the `-mhvx` and `-mhvx=flags`.

Note

The 64-byte mode will soon be deprecated, and the compiler will display a warning message: `warning: The HVX vector length of 64 Bytes will soon be deprecated. Please switch to 128 Byte mode. [-Wdeprecated-hvx-length]`.

### Optimization

-O0
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Do not optimize. This is the default optimization setting.

-O
    -O1
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Enable a small set of optimizations. We do not recommend this optimization level for performance or code size.

-O2
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Enable optimizations for performance. Optimizations enabled at `-O2` improve performance, but they might cause a small-to-moderate increase in compiled code size.

-O3
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Enable aggressive optimizations for performance. Optimizations enabled at `-O3` improve performance, but they might cause a large increase in compiled code size.

-Os
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Enable optimizations for code size. Optimizations enabled at `-Os` reduce code size at the cost of a small-to-moderate decrease in compiled code performance.

#### Recommended options for best code size

- `-O2` (for best performance)
- `-Os` (for best code size)

### Specific optimizations

-fdata-sections
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Assign each data item to its own section.

-ffast-math
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Allows aggressive, lossy floating-point optimizations. Set `-ffp-contract=fast`.

-ffp-contract=[off|on|fast]
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Form fused floating-point operations such as fused multiply-accumulates.

- `off` - Do not fuse operations. (Default)
- `fast` - Fuse operations when possible.
- `on` - Enable the FP\_CONTRACT default pragma.

-ffunction-sections
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Assign each function item to its own section in the output file. The section is named after the function assigned to it.

-finline
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Specify the inline keyword as active.

-finline-functions
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Perform heuristically-selected inlining of functions.

-fno-zero-initialized-in-bss**
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Assign all variables that are initialized to zero to the BSS section.

-fno-merge-all-constants
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Do not merge constants.

-fomit-frame-pointer
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Do not store the stack frame pointer in a register if it is not required in a function.

-foptimize-sibling-calls
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Optimize function sibling calls and tail-recursive calls.

-fstack-protector
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Generate code that checks selected functions for buffer overflows.

-fstack-protector-all
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Generate code that checks all functions for buffer overflows.

-fstack-protector-strong
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Generate code that applies strong heuristic to check additional selected functions for buffer overflows. Additional functions checked include those with local array definitions or references to local frame addresses.
.. code-block:

-fstrict-aliasing
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Enforce the strictest possible aliasing rules for the language being compiled.

-funit-at-a-time
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Parse the entire compilation unit before beginning code generation.

-funroll-all-loops
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Unroll all loops.

-funroll-loops
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Unroll selected loops.

-fvectorize
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Enable automatic vectorization.

--param ssp-buffer-size=<size>
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Specify the minimum size (in bytes) that a buffer must be if buffer-overflow checks are to be generated for it by the `-fstack-protector options`. The default value is 8.

### Link-time optimization

**Compiler options**

-flto
    -flto=thin
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For future link-time optimization (LTO), change the output format to bitcode (see [Link-time optimization](https://docs.qualcomm.com/doc/80-N3040-23/topic/code-optimization.html#hccpp-code-optimize-link-time-optimize)) instead of object code format:

- `-flto` - Enable full LTO
- `-flto=thin` - Enable ThinLTO (for more information, see [ThinLTO](https://docs.qualcomm.com/doc/80-N3040-23/topic/code-optimization.html#hccpp-link-time-optimize-thinlto-sub))

The file extension remains .o for -c and .s for -S, but the file contains different code format.

**Linker options**

-flto-options=<>
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LTO-specific prefix to denote a linker LTO option.

-flto-options=codegen="<list of options>"
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Pass the list of options to the compiler to be used for LTO global optimization. For example, `-flto-options=codegen="-O3 -mv68"`.

This example is functionally equivalent to `-flto-options=codegen=-O3 -flto- options=codegen=-mv68`.

Note

The optimization level specified in this manner overrides individual optimization levels specified during bitcode generation, with the exception of the `-Os` (optimize for size) option.

-flto-options=cache=<path>
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Enable incremental builds with ThinLTO.

The path specifies the location where ThinLTO stores its cache. This location should be an unused directory. A good practice is to remove the contents of this directory as part of any clean operation in the build system.

-flto-options=nooptimal-preservelist
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Do not use optimal preservelist for LTO.

-flto-options=preserveall
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Preserve all symbols for LTO.

-flto-options=preserve-file=<file>
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Preserve the symbols listed in `<file>`.

-flto-options=preserve-sym=<symbol>
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Preserve the symbol for LTO.

-flto-options=save-lto-output-file=<filename>
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Save the object file produced by LTO as `<filename>`.

-flto-options=threads=<n>
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Perform LTO in several parallel threads. This mode of operation is the default mode for ThinLTO, which uses as many threads as there are cores in the system. Use this option to specify a lower number of threads.

-flto-use-as
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When combined with the -save-temps option for linker, save intermediate merged files in text assembly format, which is useful for debugging and error reporting.

-save-temps
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Save the normally-temporary intermediate files generated during compilation. Use this option for debugging.

-trace=lto
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Print information about the communication between the compiler and linker during LTO. Use this option for debugging.

### Compiler security

--analyze
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Invoke the static program analyzer (see [Static analyzer](https://docs.qualcomm.com/doc/80-N3040-23/topic/compiler-security-tools.html#hccpp-compiler-security-static-analyzer)) on the specified input files.

-analyzer-checker=<checker>
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Enable the specified checker or checker category in the static program analyzer. The checker categories are `alpha`, `core`, `cplusplus`, `debug`, and `security`. Enabling a checker category enables all the checkers in that category. For a complete list of checker names use `-analyzer-checker-help`.

Note

`-analyzer-checker` must be prefixed with `-Xclang`.

-analyzer-checker-help
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List the complete set of checkers and their categories for use in `-analyzer-checker` and `-analyzer-disable-checker`.

Note

`-analyzer-checker-help` must be prefixed with `-cc1`.

-analyzer-disable-checker=<checker>
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Disable the specified checker or checker category in the static program analyzer. The checker categories are `alpha`, `core`, `cplusplus`, `debug`, and `security`. Disabling a checker category disables all the checkers in that category.

For a complete list of checker names use `-analyzer-checker-help`.

Note

`-analyzer-disable-checker` must be prefixed with `-Xclang`.

-analyzer-output html
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Generate the static analyzer output report in HTML format.

Note

`-analyzer-output` and its argument must each be prefixed `with -Xclang`.

-analyzer-werror
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Convert all static analyzer warnings into errors.

Note

`-analyzer-werror` must be prefixed `with -Xclang`.

--compile-and-analyze <dir>
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Invoke the static program analyzer on an entire program.

The analysis report files are written to the specified directory.

To prevent the analyzer from generating HTML files and instead print a summarized report on the `stdout`, replace `dir` with the sub-flag, `--analyzer-perf`.

--compile-and-analyze-high
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Invoke the static program analyzer on an entire program with only a small list of high priority checkers.

The analysis report files are written to the specified directory. If you use the sub-flag, `--analyzer-perf`, they are printed to the `stdout`.

--compile-and-analyze-medium
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Invoke the static program analyzer on an entire program with a list of high+medium priority checkers.

The analysis report files are written to the specified directory. If you use the sub-flag, `--analyzer-perf`, they are printed to the `stdout`.

### Lightweight Instrumentation

-fprofile-lwi-generate
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Insert lightweight instrumentation probes on a basic block level. Inserts said probes in the same locations as upstream instrumentation styles.

-fprofile-lwi-generate-func
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Insert lightweight instrumentation probes at function entry and exit basic blocks. This is performed after function inlining.

-fprofile-lwi-generate-loop
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Insert lightweight instrumentation probes at loop entry and exit basic blocks.

-fprofile-lwi-fp
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Insert lightweight instrumentation probes on a basic block level, including a fingerprint per every instrumented block. Inserts said probes in the same locations as upstream instrumentation styles.

-fprofile-lwi-generate-func
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Insert lightweight instrumentation probes at function entry basic blocks, and record function fingerprint information. This is performed after function inlining.

Note

This mode does not instrument function exit blocks.

-fprofile-lwi-fp-loop
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Insert lightweight instrumentation probes at loop entry and exit basic block, with a fingerprint for every loop.

-flwi-early
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When used in conjunction with either `-fprofile-lwi-generate-func` or `-fprofile-lwi-fp-func`, insert per-function lightweight probes before
inlining.

-flwi-attr
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Allows insertion of per-function lightweight probes only into functions specifically marked with the `lwi_func` attribute.

## Control diagnostic messages

The LLVM compilers provide a number of ways to control which code constructs cause the compilers to emit errors and warning messages, and how the messages are displayed on the console.

### Control how diagnostics are displayed

When the LLVM compiler emits a diagnostic message, it includes rich information in the output and provides control over which information is printed. The LLVM compiler can print this information. The following options are used to control the information:

- A file/line/column indicator that shows exactly where the diagnostic occurs in the code.
- A categorization of the diagnostic as a note, warning, error, or fatal error.
- A text string describing the problem.
- An option indicating how to control the diagnostic (for diagnostics that support it) `[-fdiagnostics-show-option]`.
- A high-level category for the diagnostic for clients that want to group diagnostics by class (for diagnostics that support it) `[-fdiagnostics-show-category]`.
- The line of source code that the issue occurs on, along with a caret and ranges indicating the important locations `[-fcaret-diagnostics]`.
- *FixIt* information, which is a concise explanation of how to fix the problem (when the LLVM compiler is certain it knows) `[-fdiagnostics-fixit-info]`.
- A machine-parseable representation of the ranges involved (disabled by default) `[-fdiagnostics-print-source-range-info]`.

For more information on these options see [Diagnostic format](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-diag-format-sub).

### Diagnostic mappings

All diagnostics are mapped into one of the following classes:

- Ignored
- Note
- Warning
- Error
- Fatal

### Diagnostic categories

Though not shown by default, diagnostics can each be associated with a high-level category. This category is intended to make it possible to triage builds that generate a large number of errors or warnings in a grouped way.

Categories are not shown by default, but you can turn them on with the `-fdiagnostics-show-category` option (see [Diagnostic format](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-diag-format-sub)). When this option is set to name, the category is printed textually in the diagnostic output. When set to `id`, a category number is printed.

Note

You can get the mapping of category names to category identifiers by invoking the LLVM compiler with the `--print-diagnostic-categories` option.

### Control diagnostics with compiler options

The LLVM compiler can control which diagnostics are enabled through the use of options specified on the command line.

The `-W` options are used to enable warning diagnostics for specific conditions in a program. For instance, `-Wmain` will generate a warning if the compiler detects anything unusual in the declaration of function `main()`.

`-Wall` enables all the warnings defined by the LLVM compiler, and `-w` disables all of them.

Disable warnings for a specific condition by specifying the corresponding `-W<cond>` option as `-Wno-<cond>`. For instance, `-Wno-main` disables the warning normally enabled by `-Wmain`.

`-Werror=<cond>` changes the specified warning to an error (see [Warning and error messages](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-warn-err-msgs-sub)). If `-Werror` is specified
without a condition, *all* the warnings are changed to errors. `-ferror-warn` changes only the warnings that are listed in the specified text file.

`-pedantic` and `-pedantic-errors` enable diagnostics that are required by the ISO C and ISO C++ standards.

### Control diagnostics with pragmas

The LLVM compiler can also control which diagnostics are enabled through the use of pragmas in the source code. This is useful for disabling specific warnings in a section of source code. The LLVM compiler supports GCC’s pragma for compatibility with existing source code, as well as several extensions.

The pragma can control any warning that can be used from the command line. Warnings can be set to ignored, warning, error, or fatal. The following example instructs the LLVM compiler or GCC to ignore the `-Wall` warnings:

#pragma GCC diagnostic ignored "-Wall"
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In addition to all the functionality provided by GCC’s pragma, the LLVM compiler also enables you to push and pop the current warning
state. This is useful when writing a header file that will be compiled by other people, because you do not know what warning flags
they build with.

In the following example, `-Wmultichar` is ignored for only a single line of code, after which the diagnostics return to whatever state had previously existed:

#pragma clang diagnostic push
    #pragma clang diagnostic ignored "-Wmultichar"
    
    char b = 'df'; // no warning.
    
    #pragma clang diagnostic pop
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The `push` and `pop` pragmas save and restore the full diagnostic state of the compiler, regardless of how it was set. Thus, it is possible
to use `push` and `pop` around GCC-compatible diagnostics—the LLVM compiler will push and pop them appropriately, while GCC will ignore
the pushes and pops as unknown pragmas.

Note

While the LLVM compilers support the GCC pragma, the compilers and GCC do not support the same set of warnings. Thus even when using GCC-compatible pragmas there is no guarantee that they will have identical behavior on both compilers.

### Control diagnostics in system headers

Warnings are suppressed when they occur in system headers. By default, an included file is treated as a system header if it is found in an include path specified by `-isystem`, but you can override this in several ways.

- Use the `system_header` pragma to mark the current file as being a system header. No warnings will be produced from the location of the pragma onwards within the same file.

char a = 'xy'; // warning
        
        #pragma clang system_header
        
        char b = 'ab'; // no warning
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- Use the –system-header-prefix=&lt;prefix&gt; and –no-system-header-prefix=&lt;prefix&gt; options to override whether subsets of an include path are treated as system headers.

    When the name in a #include directive is found within a header search path and starts with a system prefix, the header is treated as a system header. The last prefix on the command line that matches the specified header name takes precedence.

    For example:

$ hexagon-clang -Ifoo -isystem bar  --system-header-prefix=x/ --no-system-header-prefix=x/y/
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    Here, `#include "x/a.h"` is treated as including a system header, even if the header is found in foo. And `#include "x/y/b.h"` is treated as not including a system header, even if the header is found in `bar`.

    An `#include` directive that finds a file relative to the current directory is treated as including a system header if the including file is treated as a system header.

### Enable all warnings

In addition to the traditional `-W` flags, you can enable *all* warnings by specifying the `-Weverything` option.

`-Weverything` works as expected with ``-Werror`, and it also includes the warnings from `-pedantic`.

Note

When this option is used with `-w` (which disables all warnings), `-w` takes priority.

## HVX vector operand widths

HVX is a set of Hexagon instruction extensions that support the implementation of very wide vector operations.

HVX supports two execution modes:

- In 64-byte mode, the vector operands are 512 bits wide.
- In 128-byte mode, the vector operands are 1024 bits wide.

These modes are specified at compile time using the -mhvx-length options ([Processor version](https://docs.qualcomm.com/doc/80-N3040-23/topic/use-the-compilers.html#hccpp-compiler-options-processor-version-sub)). If no `-mhvx-length` is specified, a default mode is set based on either the Hexagon processor version or the Hexagon HVX coprocessor version.

A given program source file can only contain either a 64-byte or a 128-byte vector length HVX instructions (not both). However, a single
executable can contain both Single- and Double- mode HVX instructions, as long as the mixing is done at link time, using
object files that were compiled separately for either 64-byte or a 128-byte vector length HVX instructions.

To ensure proper alignment of vector data, HVX code should always use the generic vector data types (as defined in the `hexagon_types.h` library):

- `HVX_VectorPred`
- `HVX_Vector`
- `HVX_VectorPair`

Note

For more information on HVX, see the *Qualcomm Hexagon HVX Programmer’s Reference Manual* ([References](https://docs.qualcomm.com/doc/80-N3040-23/topic/references.html)).

## HVX and floating-point code generation

HVX has the capability to generate both IEEE-754 complaint and a more speedy non-IEEE complaint code.

-mhvx-ieee-fp
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Enable Hexagon processor to generate IEEE 754 complaint floating point code.

-mno-hvx-ieee-fp
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Diasble Hexagon processor from generating IEEE 754 complaint floating point code.

-mhvx-qfloat
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Enable Hexagon processor to generate QFloat instructions. The resulting code need not be IEEE complaint; this flag is enabled by default, if you pass `-fvectorize`.

-mno-hvx-qfloat
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Disable Hexagon from generating QFloat instructions. The resulting code need not be IEEE complaint.

Note

These flags are valid on all available cores and generate an error if -mhvx is not provided on the command line.

error: -mhvx-ieee-fp requires HVX, use -mhvx/-mhvx= to enable it
    error: -mhvx-qfloat requires HVX, use -mhvx/-mhvx= to enable it
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**Floating point and v79**

On v79, however, the QFloat instructions (`-mhvx-qfloat`) can generate IEEE-754 complaint code. On v79, the following flags can be used to
generate code for various floating point modes.

C/C++ source programmers can take advantage of one of the four modes of code generation. The -mllvm -enable-xqf-gen=true flag needs to be used to select one of the four modes.

- Strict-IEEE mode

> 
> 
> - Strictly adheres to IEEE-754 standards
>     - Enabled with -mllvm -hexagon-qfloat-mode=strict-ieee
- Compliant-IEEE mode

> 
> 
> - Excludes IEEE-754 overflows and lower precision subnormals due to larger dynamic range than IEEE-754
>     - All subnormals have extra precision
>     - Results that would have resulted in infinity for IEEE-754 can be represented as a finite value in XQf
>     - Enabled with `-mllvm -hexagon-qfloat-mode=ieee`
- Lossy Subnormals mode

> 
> 
> - Results in a loss of accuracy under certain conditions
>     - Provides greater precision than a clamp of subnormals to 0
>     - When the data set excludes subnormals, the behavior is the same as Compliant-IEEE mode
>     - Default mode, but can also be enabled explicitly with `-mllvm -hexagon-qfloat-mode=lossy`
- Legacy mode

> 
> 
> - Earlier legacy mode
>     - Results in 1-bit accuracy loss compared to IEEE-754
>     - Enabled with -mllvm -hexagon-qfloat-mode=legacy
>     - Equivalent to generated code on cores older than v79

Note

If you pass, `-mllvm -enable-xqf-gen=true`, Lossy Subnormals mode will be the default; without this flag, Legacy mode is the default mode.

**Example**

In order to generate strict ieee-754 complaint code, use

-mhvx -mhvx-qfloat -mllvm - enable-xqf-gen=true -mllvm -hexagon-qfloat-mode=strict-ieee
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`-mhvx-ieee-fp -mllvm -enable-xqf-gen=true` is internally lowered to generate code for Complaint-IEEE mode. Users can override the code generation mode by explicitly specifying the mode from the command line.

The floating-point code that is generated out of these modes at `-O0` is not guaranteed to be accurate.

Last Published: Oct 06, 2026

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