[PATCH] Properly check linker option in LIBC_LINKER_FEATURE [BZ #28738]

[H.J. Lu]

Update LIBC_LINKER_FEATURE to also check linker warning message since
unknown linker -z option may be ignored by linker:

$ touch x.c
$ gcc -shared -Wl,-z,foobar x.c
/usr/bin/ld: warning: -z foobar ignored
$ echo $?
0
$

This fixes BZ #28738.
---
 aclocal.m4 |  8 +++++++-
 configure  | 32 ++++++++++++++++++++++++++++----
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/aclocal.m4 b/aclocal.m4
index 3a90d4f679..3e0bcdd12b 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -236,7 +236,13 @@ EOF
 		    -fPIC -shared -o conftest.so conftest.c
 		    1>&AS_MESSAGE_LOG_FD])
   then
-    libc_linker_feature=yes
+    if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp $2 -nostdlib \
+	-nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+	| grep "warning: $1 ignored" > /dev/null 2>&1; then
+      true
+    else
+      libc_linker_feature=yes
+    fi
   fi
   rm -f conftest*
 fi
diff --git a/configure b/configure
index 954bae803e..3f956cf777 100755
--- a/configure
+++ b/configure
@@ -6009,7 +6009,13 @@ EOF
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; }
   then
-    libc_linker_feature=yes
+    if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,execstack -nostdlib \
+	-nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+	| grep "warning: -z execstack ignored" > /dev/null 2>&1; then
+      true
+    else
+      libc_linker_feature=yes
+    fi
   fi
   rm -f conftest*
 fi
@@ -6039,7 +6045,13 @@ EOF
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; }
   then
-    libc_linker_feature=yes
+    if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,-z,start-stop-gc -nostdlib \
+	-nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+	| grep "warning: -z start-stop-gc ignored" > /dev/null 2>&1; then
+      true
+    else
+      libc_linker_feature=yes
+    fi
   fi
   rm -f conftest*
 fi
@@ -6070,7 +6082,13 @@ EOF
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; }
   then
-    libc_linker_feature=yes
+    if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,--depaudit,x -nostdlib \
+	-nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+	| grep "warning: --depaudit ignored" > /dev/null 2>&1; then
+      true
+    else
+      libc_linker_feature=yes
+    fi
   fi
   rm -f conftest*
 fi
@@ -6101,7 +6119,13 @@ EOF
   $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
   test $ac_status = 0; }; }
   then
-    libc_linker_feature=yes
+    if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS $no_ssp -Wl,--no-dynamic-linker -nostdlib \
+	-nostartfiles -fPIC -shared -o conftest.so conftest.c 2>&1 \
+	| grep "warning: --no-dynamic-linker ignored" > /dev/null 2>&1; then
+      true
+    else
+      libc_linker_feature=yes
+    fi
   fi
   rm -f conftest*
 fi
-- 
2.33.1