[Bug libstdc++/108568] New: FAILs in 17_intro/names.cc

[Bug libstdc++/108568] New: FAILs in 17_intro/names.cc

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108568

            Bug ID: 108568
           Summary: FAILs in 17_intro/names.cc
           Product: gcc
           Version: 13.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

On gcc112 I'm seeing
FAIL: 17_intro/names.cc (test for excess errors)
FAIL: experimental/names.cc (test for excess errors)
These are because glibc < 2.19 used __unused as field member of various
structs,
including mcontext_t in sys/ucontext.h on ppc64le.
This was changed in glibc with
https://gcc.gnu.org/pipermail/libc-alpha/2013-November/045766.html
names.cc even has
#ifdef __GLIBC_PREREQ
#if ! __GLIBC_PREREQ(2, 19)
// Glibc defines this prior to 2.19
#undef __unused
#endif
#endif
for it, but it doesn't work.  The reason is that __GLIBC_PREREQ is defined in
<features.h> but nothing included that header before this spot (it is included
later
from bits/stdc++.h).
Can't it use
#if __GLIBC__ == 1 || (__GLIBC__ == 2 && __GLIBC_MINOR__ < 19)
instead?  Or just
#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 19
(because who knows what glibc 1 actually used, that was 1996 and already in
1997 we had glibc 2.x).

[Bug libstdc++/108568] [13 Regression] FAILs in 17_intro/names.cc

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108568

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.0
            Summary|FAILs in 17_intro/names.cc  |[13 Regression] FAILs in
                   |                            |17_intro/names.cc
           Priority|P3                          |P1

--- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
__unused in the test has been added in November 2022 and the glibc 2.19 tweak
in December, so this is a regression.

[Bug libstdc++/108568] [13 Regression] FAILs in 17_intro/names.cc

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108568

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I've unpacked the glibc 1.09.1 tarball and there isn't a single reference to
__unused, so I think just the simpler version is enough.

[Bug libstdc++/108568] [13 Regression] FAILs in 17_intro/names.cc

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108568

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Except that it doesn't work either, because even the __GLIBC__ and
__GLIBC_MINOR__ macros are defined in glibc headers.
--- a/libstdc++-v3/testsuite/17_intro/names.cc
+++ b/libstdc++-v3/testsuite/17_intro/names.cc
@@ -252,12 +252,15 @@
 #undef y
 #endif

-#ifdef __GLIBC_PREREQ
-#if ! __GLIBC_PREREQ(2, 19)
+#if defined (__linux__) || defined (__gnu_hurd__)
+#if __has_include(<features.h>)
+#include <features.h>
+#if __GLIBC__ == 2 && __GLIBC_MINOR__ < 19
 // Glibc defines this prior to 2.19
 #undef __unused
 #endif
 #endif
+#endif

 #if __has_include(<newlib.h>)
 // newlib's <sys/cdefs.h> defines these as macros.
seems to work.  __GLIBC_PREREQ was introduced only 3 years after first glibc
2.x release.

[Bug libstdc++/108568] [13 Regression] FAILs in 17_intro/names.cc

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108568

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jakub Jelinek <jakub@gcc.gnu.org>:

https://gcc.gnu.org/g:815e5740162d2d0b7b54031f72c201065016d58c

commit r13-5461-g815e5740162d2d0b7b54031f72c201065016d58c
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Fri Jan 27 20:11:20 2023 +0100

    libstdc++: Fix up FAIL in 17_intro/names.cc on glibc < 2.19 [PR108568]

    On gcc112 which has glibc 2.17 I've noticed
    FAIL: 17_intro/names.cc (test for excess errors)
    FAIL: experimental/names.cc (test for excess errors)
    These are because glibc < 2.19 used __unused as field member of various
structs,
    including mcontext_t in sys/ucontext.h on ppc64le.
    This was changed in glibc with
    https://gcc.gnu.org/pipermail/libc-alpha/2013-November/045766.html
    names.cc even has
     #ifdef __GLIBC_PREREQ
     #if ! __GLIBC_PREREQ(2, 19)
     // Glibc defines this prior to 2.19
     #undef __unused
     #endif
     #endif
    for it, but it doesn't work.  The reason is that __GLIBC_PREREQ is defined
in
    <features.h> but nothing included that header before this spot (it is
included later
    from bits/stdc++.h).

    The following patch on Linux/Hurd conditionally includes features.h to get
    the needed macros before deciding if __unused should be undefined or not.
    If needed, I could use __GLIBC_PREREQ then but would need to check if it is
    defined and between 1996 and 1999 it wasn't.

    2023-01-27  Jakub Jelinek  <jakub@redhat.com>

            PR libstdc++/108568
            * testsuite/17_intro/names.cc (__unused): For linux or GNU hurd
            include features.h if present and then check __GLIBC__ and
            __GLIBC_MINOR__ macros for glibc prior to 2.19, instead of testing
            __GLIBC_PREREQ which isn't defined yet.

[Bug libstdc++/108568] [13 Regression] FAILs in 17_intro/names.cc

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108568

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

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

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Fixed.