[Bug nptl/27714] New: pthread_setspecific missing attribute access none

[Bug nptl/27714] New: pthread_setspecific missing attribute access none

[msebor at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27714

            Bug ID: 27714
           Summary: pthread_setspecific missing attribute access none
           Product: glibc
           Version: unspecified
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: nptl
          Assignee: unassigned at sourceware dot org
          Reporter: msebor at gmail dot com
                CC: drepper.fsp at gmail dot com
  Target Milestone: ---

GCC 11 has enhanced -Wmaybe-uninitialized to trigger when the address of an
uninitialized object is passed to a const pointer function parameter.  The
assumption is that the function will most likely read the referenced object. 
As a result, when compiled with GCC 11, code that passes such an address to
pthread_setspecific() such as the test case below triggers the warning.  This
has caused the following failure in GCC
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99984.

$ cat z.c && gcc -S -Wall z.c 
#include <pthread.h>

void f (pthread_key_t key)
{
  int x;
  pthread_setspecific (key, &x);
}
z.c: In function ‘f’:
z.c:6:3: warning: ‘x’ may be used uninitialized [-Wmaybe-uninitialized]
    6 |   pthread_setspecific (key, &x);
      |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from z.c:1:
/usr/include/pthread.h:1123:12: note: by argument 2 of type ‘const void *’ to
‘pthread_setspecific’ declared here
 1123 | extern int pthread_setspecific (pthread_key_t __key,
      |            ^~~~~~~~~~~~~~~~~~~
z.c:5:7: note: ‘x’ declared here
    5 |   int x;
      |       ^

(The same warning is triggered when the result of malloc() is passed to the
function.)

To avoid the warning in calls to functions like pthread_setspecific that don't
read the object GCC 11 also extends attribute access to accept a new mode:
none.  Glibc should make use of the attribute in the declaration of the
function (and any others like it).

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[Bug nptl/27714] pthread_setspecific missing attribute access none

[msebor at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27714

--- Comment #1 from Martin Sebor <msebor at gmail dot com> ---
Patch: https://sourceware.org/pipermail/libc-alpha/2021-April/125358.html

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[Bug nptl/27714] pthread_setspecific missing attribute access none

[msebor at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27714

Martin Sebor <msebor at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|UNCONFIRMED                 |RESOLVED

--- Comment #2 from Martin Sebor <msebor at gmail dot com> ---
Fixed in https://sourceware.org/pipermail/glibc-cvs/2021q2/072962.html.

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[Bug nptl/27714] pthread_setspecific missing attribute access none

[hjl.tools at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27714

H.J. Lu <hjl.tools at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
                 CC|                            |hjl.tools at gmail dot com
   Last reconfirmed|                            |2021-04-28
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |---

--- Comment #3 from H.J. Lu <hjl.tools at gmail dot com> ---
With GCC 11, now I got

tst-tsd3.c: In function ‘tf’:
tst-tsd3.c:71:7: error: ‘pthread_setspecific’ expecting 1 byte in a region of
size 0 [-Werror=stringop-overread]
   71 |   if (pthread_setspecific (key1, (void *) 1l) != 0
      |       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../include/pthread.h:1,
                 from tst-tsd3.c:20:
../sysdeps/nptl/pthread.h:1184:12: note: in a call to function
‘pthread_setspecific’ declared with attribute ‘access (none, 2)’
 1184 | extern int pthread_setspecific (pthread_key_t __key,
      |            ^~~~~~~~~~~~~~~~~~~
tst-tsd3.c:72:10: error: ‘pthread_setspecific’ expecting 1 byte in a region of
size 0 [-Werror=stringop-overread]
   72 |       || pthread_setspecific (key2, (void *) 1l) != 0)
      |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../include/pthread.h:1,
                 from tst-tsd3.c:20:
../sysdeps/nptl/pthread.h:1184:12: note: in a call to function
‘pthread_setspecific’ declared with attribute ‘access (none, 2)’
 1184 | extern int pthread_setspecific (pthread_key_t __key,
      |            ^~~~~~~~~~~~~~~~~~~
tst-tsd3.c: In function ‘destr2’:
tst-tsd3.c:56:11: error: ‘pthread_setspecific’ expecting 1 byte in a region of
size 0 [-Werror=stringop-overread]
   56 |       if (pthread_setspecific (key1, (void *) 1l) != 0)
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../include/pthread.h:1,
                 from tst-tsd3.c:20:
../sysdeps/nptl/pthread.h:1184:12: note: in a call to function
‘pthread_setspecific’ declared with attribute ‘access (none, 2)’
 1184 | extern int pthread_setspecific (pthread_key_t __key,
      |            ^~~~~~~~~~~~~~~~~~~
tst-tsd3.c: In function ‘destr1’:
tst-tsd3.c:40:11: error: ‘pthread_setspecific’ expecting 1 byte in a region of
size 0 [-Werror=stringop-overread]
   40 |       if (pthread_setspecific (key2, (void *) 1l) != 0)
      |           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from ../include/pthread.h:1,
                 from tst-tsd3.c:20:
../sysdeps/nptl/pthread.h:1184:12: note: in a call to function
‘pthread_setspecific’ declared with attribute ‘access (none, 2)’
 1184 | extern int pthread_setspecific (pthread_key_t __key,
      |            ^~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
make[4]: *** [../o-iterator.mk:9:
/export/build/gnu/tools-build/glibc-lam-test/build-x86_64-linux/nptl/tst-tsd3.o]
Error 1

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[Bug nptl/27714] pthread_setspecific missing attribute access none

[msebor at gmail dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27714

Martin Sebor <msebor at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |FIXED

--- Comment #4 from Martin Sebor <msebor at gmail dot com> ---
All those warnings should be fixed as of last night:
https://sourceware.org/pipermail/glibc-cvs/2021q2/072963.html
If any are not, please open a new bug.

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[Bug nptl/27714] pthread_setspecific missing attribute access none

[khuey at kylehuey dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27714

Kyle Huey (Mozilla) <khuey at kylehuey dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |khuey at kylehuey dot com

--- Comment #5 from Kyle Huey (Mozilla) <khuey at kylehuey dot com> ---
(In reply to Martin Sebor from comment #4)
> All those warnings should be fixed as of last night:
> https://sourceware.org/pipermail/glibc-cvs/2021q2/072963.html
> If any are not, please open a new bug.

You may have fixed the warnings in gcc but now everyone downstream has to deal
with pthread_setspecific requiring a valid pointer to memory where it did not
require that before.

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