configure: Use -Wno-ignored-attributes if compiler warns about multiple aliases

clang emits an warning when a double alias redirection is used, to warn
the the original symbol will be used even when weak definition is
overridden.  However, this is a common pattern for weak_alias, where
multiple alias are set to same symbol.

Reviewed-by: Fangrui Song <maskray@google.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/configure b/configure
index adf263d..fc3d784 100755
--- a/configure
+++ b/configure
@@ -6347,6 +6347,35 @@ $as_echo "$libc_cv_mtls_dialect_gnu2" >&6; }
 config_vars="$config_vars
 have-mtls-dialect-gnu2 = $libc_cv_mtls_dialect_gnu2"
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking if -Wno-ignored-attributes is required for aliases" >&5
+$as_echo_n "checking if -Wno-ignored-attributes is required for aliases... " >&6; }
+if ${libc_cv_wno_ignored_attributes+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  cat > conftest.c <<EOF
+void __foo (void)
+{
+}
+extern __typeof (__foo) foo __attribute__ ((weak, alias ("__foo")));
+extern __typeof (__foo) bar __attribute__ ((weak, alias ("foo")));
+EOF
+libc_cv_wno_ignored_attributes=""
+if ! { ac_try='${CC-cc} $CFLAGS $CPPFLAGS -Werror -c conftest.c'
+  { { eval echo "\"\$as_me\":${as_lineno-$LINENO}: \"$ac_try\""; } >&5
+  (eval $ac_try) 2>&5
+  ac_status=$?
+  $as_echo "$as_me:${as_lineno-$LINENO}: \$? = $ac_status" >&5
+  test $ac_status = 0; }; }
+then
+  libc_cv_wno_ignored_attributes="-Wno-ignored-attributes"
+fi
+rm -f conftest*
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_wno_ignored_attributes" >&5
+$as_echo "$libc_cv_wno_ignored_attributes" >&6; }
+config_vars="$config_vars
+config-cflags-wno-ignored-attributes = $libc_cv_wno_ignored_attributes"
+
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether cc puts quotes around section names" >&5
 $as_echo_n "checking whether cc puts quotes around section names... " >&6; }
 if ${libc_cv_have_section_quotes+:} false; then :