[llvm-dev] Over-ride the compiler built-in functions .

[Umesh Kalappa via llvm-dev]

Hi All,

We are trying to override the compiler atomic builtin functions like

int  __sync_val_compare_and_swap( int *p,int x ,int y)
{
         return *p; //ignore the function semantics here
}

int main()
{
         int x = 0, y = 1;
   y = __sync_val_compare_and_swap(&x, x, y);

   return x + y;
}

clang throws the error like

test.c:1:6: error: cannot redeclare builtin function
'__sync_val_compare_and_swap'
int  __sync_val_compare_and_swap( int *p,int x ,int y)
     ^
test.c:1:6: note: '__sync_val_compare_and_swap' is a builtin with type
'void ()'
test.c:1:6: error: definition of builtin function
'__sync_val_compare_and_swap'
int  __sync_val_compare_and_swap( int *p,int x ,int y)

But GCC compiles it and we think that GCC is right here unlike clang.

We would like to hear from the community view on this.

Thank you
~Umesh
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