[Bug middle-end/69971] repetitive code with __builtin_return_address with a large level

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69971

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
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                 CC|                            |egallager at gcc dot gnu.org

--- Comment #1 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #0)
> Calling __builtin_return_address with a large argument (say due to a coding
> bug obscured by macros or template arguments) can result in resource
> exhaustion by the compiler as it emits at least one instruction for each
> level.  It seems that for levels greater some threshold GCC could emit a
> loop instead to avoid this problem (as unlikely as it may be).
> 
> The following is an example run on powerpc64le where GCC emits a stream of
> ld 9,0(9) instructions, one for each level:
> 
> $ cat t.c && /build/gcc-trunk/gcc/xgcc -B /build/gcc-trunk/gcc -S -Wall
> -Wextra -Wpedantic -o/dev/stdout t.c | grep "ld 9" | wc -l
> void* foo (void)
> {
>     void *p = __builtin_return_address (1024);
>     return p;
> }
> t.c: In function ‘foo’:
> t.c:3:11: warning: calling ‘__builtin_return_address’ with a nonzero
> argument is unsafe [-Wframe-address]
>      void *p = __builtin_return_address (1024);
>            ^
> 1027

Isn't this why the -Wframe-address warning you're getting exists in the first
place?