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Avoid -Wstringop-overflow warning in pthread_cleanup_push macros

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GCC 11 introduces a -Wstringop-overflow warning for calls to functions
with an array argument passed as a pointer to memory not large enough
for that array.  This includes the __sigsetjmp calls from
pthread_cleanup_push macros, because those use a structure in
__pthread_unwind_buf_t, which has a common initial subsequence with
jmp_buf but does not include the saved signal mask; this is OK in this
case because the second argument to __sigsetjmp is 0 so the signal
mask is not accessed.

To avoid this warning, use a function alias __sigsetjmp_cancel with
first argument an array of exactly the type used in the calls to the
function, if using GCC 11 or later.  With older compilers, continue to
use __sigsetjmp with a cast, to avoid any issues with compilers
predating the returns_twice attribute not applying the same special
handling to __sigsetjmp_cancel as to __sigsetjmp.

Tested with build-many-glibcs.py for arm-linux-gnueabi that this fixes
the testsuite build failures.
This commit is contained in:
Joseph Myers 2020-10-30 22:25:42 +00:00
parent 882774658c
commit 548f467fa1
2 changed files with 35 additions and 10 deletions
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8
misc/sys/cdefs.h
View File

@ -563,4 +563,12 @@ _Static_assert (0, "IEEE 128-bits long double requires redirection on this platf
# define __attr_access(x)
#endif
/* Specify that a function such as setjmp or vfork may return
twice. */
#if __GNUC_PREREQ (4, 1)
# define __attribute_returns_twice__ __attribute__ ((__returns_twice__))
#else
# define __attribute_returns_twice__ /* Ignore. */
#endif
#endif /* sys/cdefs.h */

35
sysdeps/nptl/pthread.h
View File

@ -512,13 +512,15 @@ extern void pthread_testcancel (void);
/* Cancellation handling with integration into exception handling. */
typedef struct
struct __cancel_jmp_buf_tag
{
struct
{
__jmp_buf __cancel_jmp_buf;
int __mask_was_saved;
} __cancel_jmp_buf[1];
};
typedef struct
{
struct __cancel_jmp_buf_tag __cancel_jmp_buf[1];
void *__pad[4];
} __pthread_unwind_buf_t __attribute__ ((__aligned__));
@ -658,8 +660,8 @@ __pthread_cleanup_routine (struct __pthread_cleanup_frame *__frame)
__pthread_unwind_buf_t __cancel_buf; \
void (*__cancel_routine) (void *) = (routine); \
void *__cancel_arg = (arg); \
int __not_first_call = __sigsetjmp ((struct __jmp_buf_tag *) (void *) \
__cancel_buf.__cancel_jmp_buf, 0); \
int __not_first_call = __sigsetjmp_cancel (__cancel_buf.__cancel_jmp_buf, \
0); \
if (__glibc_unlikely (__not_first_call)) \
{ \
__cancel_routine (__cancel_arg); \
@ -693,8 +695,8 @@ extern void __pthread_unregister_cancel (__pthread_unwind_buf_t *__buf)
__pthread_unwind_buf_t __cancel_buf; \
void (*__cancel_routine) (void *) = (routine); \
void *__cancel_arg = (arg); \
int __not_first_call = __sigsetjmp ((struct __jmp_buf_tag *) (void *) \
__cancel_buf.__cancel_jmp_buf, 0); \
int __not_first_call = __sigsetjmp_cancel (__cancel_buf.__cancel_jmp_buf, \
0); \
if (__glibc_unlikely (__not_first_call)) \
{ \
__cancel_routine (__cancel_arg); \
@ -730,9 +732,24 @@ extern void __pthread_unwind_next (__pthread_unwind_buf_t *__buf)
;
#endif
/* Function used in the macros. */
/* Function used in the macros. Calling __sigsetjmp, with its first
argument declared as an array, results in a -Wstringop-overflow
warning from GCC 11 because struct pthread_unwind_buf is smaller
than jmp_buf. The calls from the macros have __SAVEMASK set to 0,
so nothing beyond the common prefix is used and this warning is a
false positive. Use an alias with its first argument declared to
use the type in the macros if possible to avoid this warning. */
#if __GNUC_PREREQ (11, 0)
extern int __REDIRECT_NTHNL (__sigsetjmp_cancel,
(struct __cancel_jmp_buf_tag __env[1],
int __savemask),
__sigsetjmp) __attribute_returns_twice__;
#else
# define __sigsetjmp_cancel(env, savemask) \
__sigsetjmp ((struct __jmp_buf_tag *) (void *) (env), (savemask))
extern int __sigsetjmp (struct __jmp_buf_tag __env[1],
int __savemask) __THROWNL;
#endif
/* Mutex handling. */