[glibc] Fix namespace violation in stdio.h and sys/stat.h if build with optimization. [BZ #26376]

[Stefan Liebler <stli@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e1fd4bbe31581ffe6ebd79555e3cd78f77bba26b

commit e1fd4bbe31581ffe6ebd79555e3cd78f77bba26b
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Thu Aug 20 10:45:26 2020 +0200

    Fix namespace violation in stdio.h and sys/stat.h if build with optimization. [BZ #26376]
    
    If build with optimization, stdio.h and sys/stat.h are defining some inlining
    functions.  This leads to test fails if glibc is build with the following
    commands. (Note that the conformtests usually builds without optimization or
    other CFLAGS):
    <glibc>/configure CC="gcc -O3" --prefix=/usr
    make
    make subdirs=conform check
    - FAIL: conform/XPG4/stdio.h/conform
    - FAIL: conform/XPG42/stdio.h/conform
    out-files:
    ...
    PASSCOMBINED: Availability of variable optopt
    PASSCOMBINED: Type of variable optopt
        Namespace violation: "getc_unlocked"
        Namespace violation: "getchar_unlocked"
        Namespace violation: "putc_unlocked"
        Namespace violation: "putchar_unlocked"
    FAIL: Namespace of <stdio.h>
    ----------------------------------------------------------------------------
      Total number of tests   :  168
      Number of failed tests  :    1
      Number of xfailed tests :    0
      Number of skipped tests :    0
    
    - FAIL: conform/POSIX2008/sys/stat.h/conform
    out-file:
    ...
    PASSCOMBINED: Availability of function utimensat
    PASSCOMBINED: Type of function utimensat
        Namespace violation: "mknodat"
    FAIL: Namespace of <sys/stat.h>
    ----------------------------------------------------------------------------
      Total number of tests   :   97
      Number of failed tests  :    1
      Number of xfailed tests :    0
      Number of skipped tests :    0
    
    For getc_unlocked, getchar_unlocked, putc_unlocked, putchar_unlocked in stdio.h,
    those are defined "# ifdef __USE_POSIX" instead of "#ifdef __USE_POSIX199506"
    for the non-inlining declaration. See also
    "Bug 20014 - stdio.h namespace for pre-threads POSIX"
    (https://sourceware.org/bugzilla/show_bug.cgi?id=20014).
    
    For mknodat in sys/stat.h, those are defined "# ifdef __USE_ATFILE" instead of
    the additional guard "# if defined __USE_MISC || defined __USE_XOPEN_EXTENDED".

Diff:
---
 io/sys/stat.h      | 4 +++-
 libio/bits/stdio.h | 4 ++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/io/sys/stat.h b/io/sys/stat.h
index ce014d03a5..69e333656a 100644
--- a/io/sys/stat.h
+++ b/io/sys/stat.h
@@ -486,13 +486,15 @@ __NTH (mknod (const char *__path, __mode_t __mode, __dev_t __dev))
 }
 # endif
 
-# ifdef __USE_ATFILE
+# if defined __USE_MISC || defined __USE_XOPEN_EXTENDED
+#  ifdef __USE_ATFILE
 __extern_inline int
 __NTH (mknodat (int __fd, const char *__path, __mode_t __mode,
 		__dev_t __dev))
 {
   return __xmknodat (_MKNOD_VER, __fd, __path, __mode, &__dev);
 }
+#  endif
 # endif
 
 # if defined __USE_LARGEFILE64 \
diff --git a/libio/bits/stdio.h b/libio/bits/stdio.h
index da62908fd7..6745571ed5 100644
--- a/libio/bits/stdio.h
+++ b/libio/bits/stdio.h
@@ -60,7 +60,7 @@ fgetc_unlocked (FILE *__fp)
 # endif /* misc */
 
 
-# ifdef __USE_POSIX
+# ifdef __USE_POSIX199506
 /* This is defined in POSIX.1:1996.  */
 __STDIO_INLINE int
 getc_unlocked (FILE *__fp)
@@ -95,7 +95,7 @@ fputc_unlocked (int __c, FILE *__stream)
 # endif /* misc */
 
 
-# ifdef __USE_POSIX
+# ifdef __USE_POSIX199506
 /* This is defined in POSIX.1:1996.  */
 __STDIO_INLINE int
 putc_unlocked (int __c, FILE *__stream)