Add --disable-static-c++-link-check option [BZ #31412]

The current minimum GCC version of glibc build is GCC 6.2 or newer. But
building i686 glibc with GCC 6.4 on Fedora 40 failed since the C++ header
files couldn't be found which was caused by the static C++ link check
failure due to missing __divmoddi4 which was referenced in i686 libc.a
and added to GCC 7.  Add --disable-static-c++-link-check configure option
to disable the static C++ link test.  The newly built i686 libc.a can be
used by GCC 6.4 to create static C++ tests.  This fixes BZ #31412.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>

INSTALL

@@ -224,6 +224,14 @@ if 'CFLAGS' is specified it must enable optimization.  For example:
      By default for x86_64, the GNU C Library is built with the vector
      math library.  Use this option to disable the vector math library.
 
+'--disable-static-c++-link-check'
+     By default, if the C++ toolchain lacks support for static linking,
+     configure fails to find the C++ header files and the glibc build
+     fails.  Use this option to disable the static C++ link check so
+     that the C++ header files can be located.  The newly built libc.a
+     can be used to create static C++ tests if the C++ toolchain has the
+     necessary static C++ libraries.
+
 '--disable-scv'
      Disable using 'scv' instruction for syscalls.  All syscalls will
      use 'sc' instead, even if the kernel supports 'scv'.  PowerPC only.

configure

@@ -771,6 +771,7 @@ ac_user_opts='
 enable_option_checking
 with_pkgversion
 with_bugurl
+enable_static_c___link_check
 with_gd
 with_gd_include
 with_gd_lib
@@ -1440,6 +1441,8 @@ Optional Features:
   --disable-option-checking  ignore unrecognized --enable/--with options
   --disable-FEATURE       do not include FEATURE (same as --enable-FEATURE=no)
   --enable-FEATURE[=ARG]  include FEATURE [ARG=yes]
+  --disable-static-c++-link-check
+                          disable static C++ link check [default=no]
   --disable-sanity-checks really do not use threads (should not be used except
                           in special situations) [default=yes]
   --enable-shared         build shared library [default=yes if GNU ld]
@@ -3855,6 +3858,15 @@ if test -z "$CPP"; then
 fi
 
 
+# Check whether --enable-static-c++-link-check was given.
+if test ${enable_static_c___link_check+y}
+then :
+  enableval=$enable_static_c___link_check; static_cxx_link_check=$enableval
+else $as_nop
+  static_cxx_link_check=yes
+fi
+
+
 # We need the C++ compiler only for testing.
 
 
@@ -4279,10 +4291,11 @@ esac
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.beam \
     conftest$ac_exeext conftest.$ac_ext
-# Static case.
+if test $static_cxx_link_check = yes; then
-old_LDFLAGS="$LDFLAGS"
+  # Static case.
-LDFLAGS="$LDFLAGS -static"
+  old_LDFLAGS="$LDFLAGS"
-cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+  LDFLAGS="$LDFLAGS -static"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
 
 #include <iostream>
@@ -4304,7 +4317,8 @@ esac
 fi
 rm -f core conftest.err conftest.$ac_objext conftest.beam \
     conftest$ac_exeext conftest.$ac_ext
-LDFLAGS="$old_LDFLAGS"
+  LDFLAGS="$old_LDFLAGS"
+fi
 ac_ext=c
 ac_cpp='$CPP $CPPFLAGS'
 ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5'

configure.ac

@@ -52,6 +52,12 @@ fi
 AC_SUBST(cross_compiling)
 AC_PROG_CPP
 
+AC_ARG_ENABLE([static-c++-link-check],
+	      AS_HELP_STRING([--disable-static-c++-link-check],
+			     [disable static C++ link check @<:@default=no@:>@]),
+	      [static_cxx_link_check=$enableval],
+	      [static_cxx_link_check=yes])
+
 # We need the C++ compiler only for testing.
 AC_PROG_CXX
 # It's useless to us if it can't link programs (e.g. missing -lstdc++).
@@ -61,10 +67,11 @@ AC_LANG_PUSH([C++])
 AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])],
 	       [libc_cv_cxx_link_ok=yes],
 	       [libc_cv_cxx_link_ok=no])
-# Static case.
+if test $static_cxx_link_check = yes; then
-old_LDFLAGS="$LDFLAGS"
+  # Static case.
-LDFLAGS="$LDFLAGS -static"
+  old_LDFLAGS="$LDFLAGS"
-AC_LINK_IFELSE([AC_LANG_SOURCE([
+  LDFLAGS="$LDFLAGS -static"
+  AC_LINK_IFELSE([AC_LANG_SOURCE([
 #include <iostream>
 
 int
@@ -74,9 +81,10 @@ main()
   return 0;
 }
 ])],
-	       [],
+		 [],
-	       [libc_cv_cxx_link_ok=no])
+		 [libc_cv_cxx_link_ok=no])
-LDFLAGS="$old_LDFLAGS"
+  LDFLAGS="$old_LDFLAGS"
+fi
 AC_LANG_POP([C++])])
 AS_IF([test $libc_cv_cxx_link_ok != yes], [CXX=])
 

manual/install.texi

@@ -252,6 +252,14 @@ configure with @option{--disable-werror}.
 By default for x86_64, @theglibc{} is built with the vector math library.
 Use this option to disable the vector math library.
 
+@item --disable-static-c++-link-check
+By default, if the C++ toolchain lacks support for static linking,
+configure fails to find the C++ header files and the glibc build fails.
+Use this option to disable the static C++ link check so that the C++
+header files can be located.  The newly built libc.a can be used to
+create static C++ tests if the C++ toolchain has the necessary static
+C++ libraries.
+
 @item --disable-scv
 Disable using @code{scv} instruction for syscalls. All syscalls will use
 @code{sc} instead, even if the kernel supports @code{scv}. PowerPC only.