# Return values

Functions can return values up to 32 bits in size (including
structures) in register R0 and up to 64 bits in size (including
structures) in the R1:0 register pair. For return values larger than
64 bits, the caller allocates space in its frame large enough to hold
the return value.

The space is aligned according to the normal alignment rules for the
returned type ([Memory alignment](https://docs.qualcomm.com/doc/80-N3040-23/topic/data-types.html#memory-alignment)). The caller
passes an extra argument at the beginning of the parameter list (in
R0) containing an address of the allocated space.

## Example:

typedef struct {
      int a;
      int b;
      int c;
    } S;
    
    S foo(int x)
    {
      S s;
      ...
      return s;
    }
    
    void bar(int y)
    {
      S s = foo(y);
    }
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This code will be automatically converted by the compiler to the
following:

void foo(S *hidden, int x)
    {
      S s;
      ...
      *hidden = s;
    }
    
    void bar(int y)
    {
      S s;
      foo(&s, y);
    }
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Last Published: Oct 06, 2026

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