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Apply new CentOS fix for strdup null-test bug (re: 7afb30e) (#255)

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This is an update to one of Red Hat's patches. The strdup change is
from CentOS:
https://git.centos.org/rpms/ksh/blob/c8s/f/SOURCES/ksh-20120801-annocheck.patch

The reason why gcc (and also clang) optimize out the null check is
because the glibc string.h header gives 's' a nonnull attribute (in
other words, this is a glibc compatibility bug, not a compiler bug).
Clang gives the following informative warning when compiling strdup:

> /home/johno/GitRepos/KornShell/ksh/src/lib/libast/string/strdup.c:66:10: warning: nonnull parameter 's' will evaluate to 'true' on
>         return (s && (t = oldof(0, char, n = strlen(s) + 1, 0))) ? (char*)memcpy(t, s, n) : (char*)0;
>                 ^ ~~
> /usr/include/string.h:172:35: note: declared 'nonnull' here
>      __THROW __attribute_malloc__ __nonnull ((1));
>                                   ^
> /usr/include/sys/cdefs.h:303:44: note: expanded from macro '__nonnull'
> # define __nonnull(params) __attribute__ ((__nonnull__ params))

The proper fix is to rename the function in strdup.c to
'_ast_strdup'. This avoids the string.h conflict and fixes the Red
Hat bug. I've also made a similar change to getopt.c, since clang
was throwing a nonnull warning there as well.

src/lib/libast/features/map.c (which generates FEATURE/map which is
indirectly included by everything) is updated to always map getopt
to _ast_getopt and strdup to _ast_strdup.
This commit is contained in:
Johnothan King 2021-04-07 21:26:16 -07:00 • committed by GitHub
parent 0e41899b3d
commit a28507e0b1
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3 changed files with 16 additions and 12 deletions
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6
src/lib/libast/comp/getopt.c
View file

@ -43,8 +43,12 @@ char* optarg = 0;
static int lastoptind;
/*
* Avoid a null-test optimization bug caused by glibc's headers
* by naming this function '_ast_getopt' instead of 'getopt'.
*/
extern int
getopt(int argc, char* const* argv, const char* optstring)
_ast_getopt(int argc, char* const* argv, const char* optstring)
{
int n;

12
src/lib/libast/features/map.c
View file

@ -113,9 +113,12 @@ main()
#endif
printf("#undef getdate\n");
printf("#define getdate _ast_getdate\n");
#if _lib_getopt || _lib_getsubopt || _lib_getopt_long || _lib_getopt_long_only
#endif
/* libast always provides its own getopt implementation */
printf("#undef getopt\n");
printf("#define getopt _ast_getopt\n");
#if _map_libc
#if _lib_getopt || _lib_getsubopt || _lib_getopt_long || _lib_getopt_long_only
printf("#undef getsubopt\n");
printf("#define getsubopt _ast_getsubopt\n");
printf("#undef getopt_long\n");
@ -447,9 +450,6 @@ main()
printf("#undef realloc\n");
printf("#define realloc _ast_realloc\n");
printf("extern void* realloc(void*, size_t);\n");
printf("#undef strdup\n");
printf("#define strdup _ast_strdup\n");
printf("extern char* strdup(const char*);\n");
#if _lib_valloc
printf("#undef valloc\n");
printf("#define valloc _ast_valloc\n");
@ -457,6 +457,10 @@ main()
#endif
#endif
#endif
/* we always use the libast strdup implementation */
printf("#undef strdup\n");
printf("#define strdup _ast_strdup\n");
printf("extern char* strdup(const char*);\n");
/*
* overriding <stdlib.h> strto*() is problematic to say the least

10
src/lib/libast/string/strdup.c
View file

@ -51,19 +51,15 @@ __STDPP__directive pragma pp:nohide strdup
#endif
/*
* Work around a null-test optimization bug in GCC.
* Avoid a null-test optimization bug caused by glibc's headers
* by naming this function '_ast_strdup' instead of 'strdup'.
* https://bugzilla.redhat.com/1221766
*/
#pragma GCC push_options
#pragma GCC optimize ("O0")
extern char*
strdup(register const char* s)
_ast_strdup(const char* s)
{
register char* t;
register int n;
return (s && (t = oldof(0, char, n = strlen(s) + 1, 0))) ? (char*)memcpy(t, s, n) : (char*)0;
}
#pragma GCC pop_options