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GNU C Library master sources branch master updated. glibc-2.26.9000-617-g8f6f536


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- Log -----------------------------------------------------------------
http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=8f6f5362727dc93360fe37e6d4e964f386b7b8e7

commit 8f6f5362727dc93360fe37e6d4e964f386b7b8e7
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Tue Oct 10 11:12:50 2017 -0300

    Avoid build multiarch if compiler warns about mismatched alias
    
    GCC 8 emits an warning for alias for functions with incompatible types
    and it is used extensivelly for ifunc resolvers implementations in C
    (for instance on weak_alias with the internal symbol name to the
    external one or with the libc_hidden_def to set ifunc for internal
    usage).
    
    This breaks the build when the ifunc resolver is not defined using
    gcc attribute extensions (HAVE_GCC_IFUNC being 0).  Although for
    all currently architectures that have multiarch support this compiler
    options is enabled for default, there is still the option where the
    user might try build glibc with a compiler without support for such
    extension.  In this case this patch just disable the multiarch folder
    in sysdeps selections.
    
    GCC 7 and before still builds IFUNCs regardless of compiler support
    (although for the lack of attribute support debug information would
    be optimal).
    
    Checked with a build on multiarch support architectures (aarch64,
    arm, sparc, s390, powerpc, x86_64, i386) with multiarch enable
    and disable and with GCC 7 and GCC 8.
    
    	* configure.ac (libc_cv_gcc_incompatbile_alias): New define:
    	indicates whether compiler emits an warning for alias for
    	functions with incompatible types.

diff --git a/ChangeLog b/ChangeLog
index 66a500b..aa7e9a9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2017-10-20  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
+	* configure.ac (libc_cv_gcc_incompatbile_alias): New define:
+	indicates whether compiler emits an warning for alias for
+	functions with incompatible types.
+
 	[BZ #22273]
 	* sysdeps/unix/sysv/linux/spawni.c (__spawnix): Handle the case where
 	the auxiliary process is terminated by a signal before calling _exit
diff --git a/configure b/configure
index c2c9c72..6010977 100755
--- a/configure
+++ b/configure
@@ -3996,6 +3996,32 @@ fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gcc_indirect_function" >&5
 $as_echo "$libc_cv_gcc_indirect_function" >&6; }
 
+# Check if gcc warns about alias for function with incompatible types.
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if compiler warns about alias for function with incompatible types" >&5
+$as_echo_n "checking if compiler warns about alias for function with incompatible types... " >&6; }
+if ${libc_cv_gcc_incompatible_alias+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest.c <<EOF
+int __redirect_foo (const void *s, int c);
+
+__typeof (__redirect_foo) *foo_impl (void) __asm__ ("foo");
+__typeof (__redirect_foo) *foo_impl (void)
+{
+  return 0;
+}
+
+extern __typeof (__redirect_foo) foo_alias __attribute__ ((alias ("foo")));
+EOF
+libc_cv_gcc_incompatible_alias=yes
+if ${CC-cc} -Werror -c conftest.c -o conftest.o 1>&5 2>&5 ; then
+  libc_cv_gcc_incompatible_alias=no
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_gcc_incompatible_alias" >&5
+$as_echo "$libc_cv_gcc_incompatible_alias" >&6; }
+
 if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
   if test x"$multi_arch" = xyes; then
     as_fn_error $? "--enable-multi-arch support requires assembler and linker support" "$LINENO" 5
@@ -4003,12 +4029,25 @@ if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
     multi_arch=no
   fi
 fi
-if test x"$libc_cv_gcc_indirect_function" != xyes &&
-   test x"$multi_arch" = xyes; then
-  { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: --enable-multi-arch support recommends a gcc with gnu-indirect-function support.
+if test x"$libc_cv_gcc_indirect_function" != xyes; then
+  # GCC 8+ emits a warning for alias with incompatible types and it might
+  # fail to build ifunc resolvers aliases to either weak or internal
+  # symbols.  Disables multiarch build in this case.
+  if test x"$libc_cv_gcc_incompatible_alias" == xyes; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: gcc emits a warning for alias between functions of incompatible types" >&5
+$as_echo "$as_me: WARNING: gcc emits a warning for alias between functions of incompatible types" >&2;}
+    if test x"$multi_arch" = xyes; then
+      as_fn_error $? "--enable-multi-arch support requires a gcc with gnu-indirect-function support" "$LINENO" 5
+    fi
+    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: Multi-arch is disabled." >&5
+$as_echo "$as_me: WARNING: Multi-arch is disabled." >&2;}
+    multi_arch=no
+  elif test x"$multi_arch" = xyes; then
+    { $as_echo "$as_me:${as_lineno-$LINENO}: WARNING: --enable-multi-arch support recommends a gcc with gnu-indirect-function support.
 Please use a gcc which supports it by default or configure gcc with --enable-gnu-indirect-function" >&5
 $as_echo "$as_me: WARNING: --enable-multi-arch support recommends a gcc with gnu-indirect-function support.
 Please use a gcc which supports it by default or configure gcc with --enable-gnu-indirect-function" >&2;}
+  fi
 fi
 multi_arch_d=
 if test x"$multi_arch" != xno; then
diff --git a/configure.ac b/configure.ac
index 195e81a..148f7d1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -634,6 +634,26 @@ if ${CC-cc} -c conftest.c -o conftest.o 1>&AS_MESSAGE_LOG_FD \
 fi
 rm -f conftest*])
 
+# Check if gcc warns about alias for function with incompatible types.
+AC_CACHE_CHECK([if compiler warns about alias for function with incompatible types],
+	       libc_cv_gcc_incompatible_alias, [dnl
+cat > conftest.c <<EOF
+int __redirect_foo (const void *s, int c);
+
+__typeof (__redirect_foo) *foo_impl (void) __asm__ ("foo");
+__typeof (__redirect_foo) *foo_impl (void)
+{
+  return 0;
+}
+
+extern __typeof (__redirect_foo) foo_alias __attribute__ ((alias ("foo")));
+EOF
+libc_cv_gcc_incompatible_alias=yes
+if ${CC-cc} -Werror -c conftest.c -o conftest.o 1>&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD ; then
+  libc_cv_gcc_incompatible_alias=no
+fi
+rm -f conftest*])
+
 if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
   if test x"$multi_arch" = xyes; then
     AC_MSG_ERROR([--enable-multi-arch support requires assembler and linker support])
@@ -641,10 +661,21 @@ if test x"$libc_cv_ld_gnu_indirect_function" != xyes; then
     multi_arch=no
   fi
 fi
-if test x"$libc_cv_gcc_indirect_function" != xyes &&
-   test x"$multi_arch" = xyes; then
-  AC_MSG_WARN([--enable-multi-arch support recommends a gcc with gnu-indirect-function support.
+if test x"$libc_cv_gcc_indirect_function" != xyes; then
+  # GCC 8+ emits a warning for alias with incompatible types and it might
+  # fail to build ifunc resolvers aliases to either weak or internal
+  # symbols.  Disables multiarch build in this case.
+  if test x"$libc_cv_gcc_incompatible_alias" == xyes; then
+    AC_MSG_WARN([gcc emits a warning for alias between functions of incompatible types])
+    if test x"$multi_arch" = xyes; then
+      AC_MSG_ERROR([--enable-multi-arch support requires a gcc with gnu-indirect-function support])
+    fi
+    AC_MSG_WARN([Multi-arch is disabled.])
+    multi_arch=no
+  elif test x"$multi_arch" = xyes; then
+    AC_MSG_WARN([--enable-multi-arch support recommends a gcc with gnu-indirect-function support.
 Please use a gcc which supports it by default or configure gcc with --enable-gnu-indirect-function])
+  fi
 fi
 multi_arch_d=
 if test x"$multi_arch" != xno; then

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog    |    4 ++++
 configure    |   45 ++++++++++++++++++++++++++++++++++++++++++---
 configure.ac |   37 ++++++++++++++++++++++++++++++++++---
 3 files changed, 80 insertions(+), 6 deletions(-)


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