On Sat, Feb 24, 2018 at 08:01:28PM +0100, Mikael Magnusson wrote: > I figured out this was because of -foptimize-strlen which somehow > causes calloc() to recurse infinitely and crash (with -O2 which also > enables -foptimize-sibling-calls it just hangs with no crash because > it doesn't consume extra stack, i presume). What I don't know is how > to fix it, or the causal relationship between strlen optimization and > calloc recursing infinitely. I've tried gcc 5.4, 6.2 and 6.4 with the > same result. Compiling only Src/mem.c with the problematic flag is > enough so it's something in there, but removing the one strlen() call > in the file has no effect. I am also seeing the same behavior, and to be completely honest I have no idea how strlen() is related either. Some testing in gdb did show that you were right; the problem is a loop caused by a repeated jump back to line 1719, which definitely lines up with the `-foptimize-sibling-calls` part. The only fix I could find which didn't requiring substantial reimplementation of the memory management functions was to replace the malloc() call in calloc() with realloc() instead. With a NULL `p` argument realloc() behaves exactly the same as malloc() does, and (at least on my system) gcc doesn't seem to consider realloc() a candidate for sibling call optimizations; give this patch a try and _hopefully_ this is a viable solution. Signed-off-by: Joey Pabalinas 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/Src/mem.c b/Src/mem.c index 840bbb6e4a4eb6fd73..8b0dafed6fdae35a61 100644 --- a/Src/mem.c +++ b/Src/mem.c @@ -1714,12 +1714,18 @@ MALLOC_RET_T calloc(MALLOC_ARG_T n, MALLOC_ARG_T size) { long l; - char *r; + char *r = NULL; if (!(l = n * size)) return (MALLOC_RET_T) m_high; - r = malloc(l); + /* + * use realloc() (with a NULL `p` argument it behaves exactly the same + * as malloc() does) to prevent an infinite loop caused by sibling-call + * optimizations (the malloc() call would otherwise be replaced by an + * unconditional branch back to line 1719 ad infinitum). + */ + r = realloc(r, l); memset(r, 0, l); -- 2.16.2