Get rid of Werror=maybe-uninitialized in clock_nanosleep.c.

Message ID 4c7fda1e-d0fe-d373-9694-d1ce09084ec2@linux.ibm.com
State New
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  • Get rid of Werror=maybe-uninitialized in clock_nanosleep.c.
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Commit Message

Stefan Liebler Dec. 3, 2019, 8:50 a.m.
Hi,

If build with -O3 on s390 (31bit) on kernels < 5.1, there are the 
following werrors:
../sysdeps/unix/sysv/linux/clock_nanosleep.c:91:12: error: ‘*((void 
*)&trem64+12)’ may be used uninitialized in this function 
[-Werror=maybe-uninitialized]
*rem = valid_timespec64_to_timespec (trem64);

../include/time.h:264:15: error: ‘trem64’ may be used uninitialized in 
this function [-Werror=maybe-uninitialized]
ts.tv_sec = (time_t) ts64.tv_sec;

This patch moves the calculation of r before the if condition.  Then GCC
recognizes that the condition here and in __clock_nanosleep equals and that
trem64 in __clock_nanosleep is initialized.

Bye
Stefan

Comments

Stefan Liebler Dec. 9, 2019, 12:59 p.m. | #1
On 12/3/19 9:50 AM, Stefan Liebler wrote:
> Hi,

> 

> If build with -O3 on s390 (31bit) on kernels < 5.1, there are the 

> following werrors:

> ../sysdeps/unix/sysv/linux/clock_nanosleep.c:91:12: error: ‘*((void 

> *)&trem64+12)’ may be used uninitialized in this function 

> [-Werror=maybe-uninitialized]

> *rem = valid_timespec64_to_timespec (trem64);

> 

> ../include/time.h:264:15: error: ‘trem64’ may be used uninitialized in 

> this function [-Werror=maybe-uninitialized]

> ts.tv_sec = (time_t) ts64.tv_sec;

> 

> This patch moves the calculation of r before the if condition.  Then GCC

> recognizes that the condition here and in __clock_nanosleep equals and that

> trem64 in __clock_nanosleep is initialized.

> 

> Bye

> Stefan


ping
Stefan Liebler Dec. 13, 2019, 12:43 p.m. | #2
On 12/9/19 1:59 PM, Stefan Liebler wrote:
> On 12/3/19 9:50 AM, Stefan Liebler wrote:

>> Hi,

>>

>> If build with -O3 on s390 (31bit) on kernels < 5.1, there are the 

>> following werrors:

>> ../sysdeps/unix/sysv/linux/clock_nanosleep.c:91:12: error: ‘*((void 

>> *)&trem64+12)’ may be used uninitialized in this function 

>> [-Werror=maybe-uninitialized]

>> *rem = valid_timespec64_to_timespec (trem64);

>>

>> ../include/time.h:264:15: error: ‘trem64’ may be used uninitialized in 

>> this function [-Werror=maybe-uninitialized]

>> ts.tv_sec = (time_t) ts64.tv_sec;

>>

>> This patch moves the calculation of r before the if condition.  Then GCC

>> recognizes that the condition here and in __clock_nanosleep equals and 

>> that

>> trem64 in __clock_nanosleep is initialized.

>>

>> Bye

>> Stefan

> 

> ping

> 

ping
Stefan Liebler Jan. 8, 2020, 7:47 a.m. | #3
On 12/13/19 1:43 PM, Stefan Liebler wrote:
> On 12/9/19 1:59 PM, Stefan Liebler wrote:

>> On 12/3/19 9:50 AM, Stefan Liebler wrote:

>>> Hi,

>>>

>>> If build with -O3 on s390 (31bit) on kernels < 5.1, there are the 

>>> following werrors:

>>> ../sysdeps/unix/sysv/linux/clock_nanosleep.c:91:12: error: ‘*((void 

>>> *)&trem64+12)’ may be used uninitialized in this function 

>>> [-Werror=maybe-uninitialized]

>>> *rem = valid_timespec64_to_timespec (trem64);

>>>

>>> ../include/time.h:264:15: error: ‘trem64’ may be used uninitialized 

>>> in this function [-Werror=maybe-uninitialized]

>>> ts.tv_sec = (time_t) ts64.tv_sec;

>>>

>>> This patch moves the calculation of r before the if condition.  Then GCC

>>> recognizes that the condition here and in __clock_nanosleep equals 

>>> and that

>>> trem64 in __clock_nanosleep is initialized.

>>>

>>> Bye

>>> Stefan

>>

>> ping

>>

> ping

> 

This warning does not occur anymore starting with the commit "Linux: Fix 
clock_nanosleep time64 check" 
https://sourceware.org/git/?p=glibc.git;a=commit;h=b03688bfbb072f42970747bc2e6362c24b4b7ee8

Patch

commit 1d23f5b16a99281faa523e21e137472059bc3f5f
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Mon Dec 2 11:47:00 2019 +0100

    Get rid of Werror=maybe-uninitialized in clock_nanosleep.c.
    
    If build with -O3 on s390 (31bit) on kernels < 5.1, there are the following werrors:
    ../sysdeps/unix/sysv/linux/clock_nanosleep.c:91:12: error: ‘*((void *)&trem64+12)’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
         *rem = valid_timespec64_to_timespec (trem64);
    
    ../include/time.h:264:15: error: ‘trem64’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
       ts.tv_sec = (time_t) ts64.tv_sec;
    
    This patch moves the calculation of r before the if condition.  Then GCC
    recognizes that the condition here and in __clock_nanosleep equals and that
    trem64 in __clock_nanosleep is initialized.

diff --git a/sysdeps/unix/sysv/linux/clock_nanosleep.c b/sysdeps/unix/sysv/linux/clock_nanosleep.c
index fc47c58ee7..c9e1072354 100644
--- a/sysdeps/unix/sysv/linux/clock_nanosleep.c
+++ b/sysdeps/unix/sysv/linux/clock_nanosleep.c
@@ -47,6 +47,9 @@  __clock_nanosleep_time64 (clockid_t clock_id, int flags, const struct __timespec
 # endif
   r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err, clock_id,
                                flags, req, rem);
+
+  r = (INTERNAL_SYSCALL_ERROR_P (r, err)
+       ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
 #else
 # ifdef __NR_clock_nanosleep_time64
   r = INTERNAL_SYSCALL_CANCEL (clock_nanosleep_time64, err, clock_id,
@@ -68,12 +71,16 @@  __clock_nanosleep_time64 (clockid_t clock_id, int flags, const struct __timespec
   r =  INTERNAL_SYSCALL_CANCEL (clock_nanosleep, err, clock_id, flags,
                                 &ts32, &tr32);
 
-  if (r == -EINTR && rem != NULL && (flags & TIMER_ABSTIME) == 0)
+  /* Calculate r before the following if condition.  Then GCC recognizes
+     that the condition here and in __clock_nanosleep equals and that
+     trem64 in __clock_nanosleep is initialized.  */
+  r = (INTERNAL_SYSCALL_ERROR_P (r, err)
+       ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
+  if (r == EINTR && rem != NULL && (flags & TIMER_ABSTIME) == 0)
     *rem = valid_timespec_to_timespec64 (tr32);
 #endif /* __ASSUME_TIME64_SYSCALLS */
 
-  return (INTERNAL_SYSCALL_ERROR_P (r, err)
-	  ? INTERNAL_SYSCALL_ERRNO (r, err) : 0);
+  return r;
 }
 
 #if __TIMESIZE != 64