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MINOR: debug: make ABORT_NOW() store the caller's line number when using abort

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Placing DO_NOT_FOLD() before abort() only works in -O2 but not in -Os which
continues to place only 5 calls to abort() in h3.o for call places. The
approach taken here is to replace abort() with a new function that wraps
it and stores the line number in the stack. This slightly increases the
code size (+0.1%) but when unwinding a crash, the line number remains
present now. This is a very low cost, especially if we consider that
DEBUG_USE_ABORT is almost only used by code coverage tools and occasional
debugging sessions.
This commit is contained in:
Willy Tarreau 2024-02-02 17:09:09 +01:00
parent 2bb192ba91
commit d480b7be96
1 changed files with 18 additions and 1 deletions
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19
include/haproxy/bug.h
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@ -87,7 +87,24 @@ static inline __attribute((always_inline)) void ha_crash_now(void)
#ifdef DEBUG_USE_ABORT
/* abort() is better recognized by code analysis tools */
#define ABORT_NOW() do { DUMP_TRACE(); abort(); } while (0)
/* abort() is generally tagged noreturn, so there's no 100% safe way to prevent
* the compiler from doing a tail-merge here. Tests show that stopping folding
* just before calling abort() does work in practice at -O2, increasing the
* number of abort() calls in h3.o from 18 to 26, probably because there's no
* more savings to be made by replacing a call with a jump. However, as -Os it
* drops to 5 regardless of the build option. In order to help here, instead we
* wrap abort() into another function, with the line number stored into a local
* variable on the stack and we pretend to use it, so that unwinding the stack
* from abort() will reveal its value even if the call was folded.
*/
static __attribute__((noinline,noreturn,unused)) void abort_with_line(uint line)
{
DISGUISE(&line);
abort();
}
#define ABORT_NOW() do { DUMP_TRACE(); abort()_with_line(__LINE__); } while (0)
#else
/* More efficient than abort() because it does not mangle the
* stack and stops at the exact location we need.