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fix realpath when stdlib.h is included before limits.h 

If program includes stdlib.h before limits.h without _XOPEN_SOURCE,
_GNU_SOURCE or _BSD_SOURCE explicitly set, then will it always trigger
the trap with musl libc.

This is becase stdlib.h will pull in features.h which will set
_GNU_SOURCE. This means that the fortify stdlib.h will not include
limits.h but it will still trigger the fortified realpath(), but without
PATH_MAX set.

We fix this by including system stdlib.h before testing if limits.h
should be included.

Since PATH_MAX is known at compile time we can also error at compile
time, instead of compiling a broken realpath().
This commit is contained in:
Natanael Copa 2015-05-07 14:50:03 +02:00 committed by sin
parent c7e82d4863
commit c2bb9e106a
1 changed files with 3 additions and 3 deletions
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6
include/stdlib.h
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@ -1,12 +1,12 @@
#ifndef _FORTIFY_STDLIB_H
#define _FORTIFY_STDLIB_H
#include_next <stdlib.h>
#if defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
#include_next <limits.h>
#endif
#include_next <stdlib.h>
#if defined(_FORTIFY_SOURCE) && _FORTIFY_SOURCE > 0 && defined(__OPTIMIZE__) && __OPTIMIZE__ > 0
#ifdef __cplusplus
@ -23,7 +23,7 @@ char *realpath(const char *path, char *resolved)
if (resolved) {
#ifndef PATH_MAX
__builtin_trap();
# error PATH_MAX unset. A fortified realpath will not work.
#else
bos = __builtin_object_size(resolved, 0);
if (PATH_MAX > bos)