From: Emil Velikov <emil.l.velikov@gmail.com>
Date: Sun, 15 Sep 2024 00:40:14 +0000 (+0100)
Subject: build: check for __xstat declarations
X-Git-Tag: v34~336
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0766f541927f50879599e62fdaa5a2e51b9791d3;p=thirdparty%2Fkmod.git

build: check for __xstat declarations

Currently we check the function is resolved at link time. Although what
we really care is if the headers are silently transposing any of our stat
calls to __xstat{,64}. If so, we'd want to wrap the latter functions.

As the now-removed comment says, glibc 2.33 was the first release to no
longer have static inline wrappers that do the transposition. See the
glibc commit 8ed005daf0ab ("Remove stat wrapper functions, move them to
exported symbols") for more details.

So change the checking to check_decl/has_header_symbol and keep them for
distributions with older glibc.

NOTE: to summarise/contrast this wrt the previous open64, etc
 - here: we had inline wrappers and declarations (as below)
 - others: no inline wrappers and optionally declarations

glibc 2.32
extern ... __xstat(); extern inline stat(...) { return __xstat(...); }

glibc 2.33
extern stat(...);

Note we group the 64 variant as well, since the codepath has been
identical (wrt core logic) to the normal __xstat().

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/131
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
---

diff --git a/configure.ac b/configure.ac
index 39e33690..15def643 100644
--- a/configure.ac
+++ b/configure.ac
@@ -39,7 +39,6 @@ AC_PROG_CC_C99
 # Function and structure checks
 #####################################################################
 
-AC_CHECK_FUNCS_ONCE(__xstat)
 AC_CHECK_FUNCS_ONCE([open64 stat64 fopen64 __stat64_time64])
 AC_CHECK_FUNCS_ONCE([__secure_getenv secure_getenv])
 
@@ -48,16 +47,13 @@ CC_CHECK_FUNC_BUILTIN([__builtin_types_compatible_p])
 CC_CHECK_FUNC_BUILTIN([__builtin_uaddl_overflow], [ ], [ ])
 CC_CHECK_FUNC_BUILTIN([__builtin_uaddll_overflow], [ ], [ ])
 
-# Non glibc compilers (musl and newer versions of bionic) do not need
-# the 64 LFS API wrapping.
-AC_CHECK_DECLS_ONCE([[__GLIBC__]], [], [], [[#include <features.h>]])
-
 # dietlibc doesn't have st.st_mtim struct member
 AC_CHECK_MEMBERS([struct stat.st_mtim], [], [], [#include <sys/stat.h>])
 
 # basename may be only available in libgen.h with the POSIX behavior,
 # not desired here
 AC_CHECK_DECLS_ONCE([[basename]], [], [], [[#include <string.h>]])
+AC_CHECK_DECLS_ONCE([[__xstat]], [], [], [[#include <sys/stat.h]])
 
 AC_MSG_CHECKING([whether _Static_assert() is supported])
 AC_COMPILE_IFELSE(
diff --git a/meson.build b/meson.build
index 047e9647..16ff67b9 100644
--- a/meson.build
+++ b/meson.build
@@ -34,7 +34,6 @@ cdata.set10('_GNU_SOURCE', true)
 ################################################################################
 
 _funcs = [
-  '__xstat',
   'open64', 'stat64', 'fopen64', '__stat64_time64',
   '__secure_getenv', 'secure_getenv',
 ]
@@ -88,11 +87,12 @@ endforeach
 # not desired here
 _decls = [
   ['basename', 'string.h'],
+  ['__xstat', 'sys/stat.h'],
 ]
 foreach tuple : _decls
   decl = tuple[0]
   header = tuple[1]
-  glibc = cc.has_header_symbol(header, decl, args : '-D_GNU_SOURCE')
+  have  = cc.has_header_symbol(header, decl, args : '-D_GNU_SOURCE')
   cdata.set10('HAVE_DECL_@0@'.format(decl.to_upper()), have)
 endforeach
 
diff --git a/testsuite/path.c b/testsuite/path.c
index 26e0f4bc..9b1f97a9 100644
--- a/testsuite/path.c
+++ b/testsuite/path.c
@@ -152,15 +152,7 @@ TS_EXPORT int open ## suffix (const char *path, int flags, ...)	\
 	return _fn(p, flags);					\
 }
 
-/*
- * wrapper template for __xstat family
- * This family got deprecated/dropped in glibc 2.32.9000, but we still need
- * to keep it for a while for programs that were built against previous versions
- */
 #define WRAP_VERSTAT(prefix, suffix)			    \
-TS_EXPORT int prefix ## stat ## suffix (int ver,	    \
-			      const char *path,		    \
-	                      struct stat ## suffix *st);   \
 TS_EXPORT int prefix ## stat ## suffix (int ver,	    \
 			      const char *path,		    \
 	                      struct stat ## suffix *st)    \
@@ -205,9 +197,7 @@ WRAP_2ARGS(int, -1, __stat64_time64, void *);
 WRAP_OPEN(64);
 #endif
 
-#ifdef HAVE___XSTAT
+#if HAVE_DECL___XSTAT
 WRAP_VERSTAT(__x,);
-#if HAVE_DECL___GLIBC__
 WRAP_VERSTAT(__x,64);
 #endif
-#endif