[Bug libc/27476] New: getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull

[Bug libc/27476] New: getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull

[slyfox at inbox dot ru]

https://sourceware.org/bugzilla/show_bug.cgi?id=27476

            Bug ID: 27476
           Summary: getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull
           Product: glibc
           Version: 2.33
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libc
          Assignee: unassigned at sourceware dot org
          Reporter: slyfox at inbox dot ru
                CC: adhemerval.zanella at linaro dot org, drepper.fsp at gmail dot com,
                    fweimer at redhat dot com
  Target Milestone: ---

Extracted from https://github.com/libarchive/libarchive/issues/1498. Small
example:

$ cat a.c
#include <limits.h> /* PATH_MAX */
#include <unistd.h> /* getcwd() */

// from https://github.com/libarchive/libarchive/issues/1498
char * bug(void) {
    return getcwd(NULL, PATH_MAX);/* Solaris getcwd needs the size. */
}

$ gcc-10.2.0 -O2 -c a.c -O2 -Wall -Werror=nonnull -D_FORTIFY_SOURCE=0
<command-line>: warning: "_FORTIFY_SOURCE" redefined
<built-in>: note: this is the location of the previous definition
a.c: In function 'bug':
a.c:6:12: error: argument 1 is null but the corresponding size argument 2 value
is 4096 [-Werror=nonnull]
    6 |     return getcwd(NULL, PATH_MAX);/* Solaris getcwd needs the size. */
      |            ^~~~~~~~~~~~~~~~~~~~~~
In file included from a.c:2:
/usr/include/unistd.h:520:14: note: in a call to function 'getcwd' declared
with attribute 'write_only (1, 2)'
  520 | extern char *getcwd (char *__buf, size_t __size) __THROW __wur
      |              ^~~~~~
cc1: some warnings being treated as errors

I see https://sourceware.org/PR26545 where there is a discussion of possibly
changing the behaviour of the function.

I'm opening the bug to consider at least removing the warning whic the
behaviour is valid

Thanks!.

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[Bug libc/27476] getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull

[sam at gentoo dot org]

https://sourceware.org/bugzilla/show_bug.cgi?id=27476

Sam James <sam at gentoo dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |sam at gentoo dot org

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[Bug libc/27476] getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull

[eb at emlix dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=27476

Rolf Eike Beer <eb at emlix dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |eb at emlix dot com

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[Bug libc/27476] getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull

[aurelien at aurel32 dot net]

https://sourceware.org/bugzilla/show_bug.cgi?id=27476

Aurelien Jarno <aurelien at aurel32 dot net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aurelien at aurel32 dot net

--- Comment #1 from Aurelien Jarno <aurelien at aurel32 dot net> ---
Proposed patch here:
https://sourceware.org/pipermail/libc-alpha/2021-September/130857.html

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[Bug libc/27476] getcwd(NULL, PATH_MAX) generates warnings on -Wnonnull

[glaubitz at physik dot fu-berlin.de]

https://sourceware.org/bugzilla/show_bug.cgi?id=27476

John Paul Adrian Glaubitz <glaubitz at physik dot fu-berlin.de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |glaubitz at physik dot fu-berlin.d
                   |                            |e

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