1 files changed, 38 insertions, 23 deletions

diff --git a/gl/m4/warn-on-use.m4 b/gl/m4/warn-on-use.m4
index e43beebd..10649c5c 100644
--- a/gl/m4/warn-on-use.m4
+++ b/gl/m4/warn-on-use.m4
@@ -1,11 +1,13 @@
-# warn-on-use.m4 serial 5
-dnl Copyright (C) 2010-2013 Free Software Foundation, Inc.
+# warn-on-use.m4 serial 10
+dnl Copyright (C) 2010-2023 Free Software Foundation, Inc.
 dnl This file is free software; the Free Software Foundation
 dnl gives unlimited permission to copy and/or distribute it,
 dnl with or without modifications, as long as this notice is preserved.
 
 # gl_WARN_ON_USE_PREPARE(INCLUDES, NAMES)
 # ---------------------------------------
+# If the module 'posixcheck' is in use:
+#
 # For each whitespace-separated element in the list of NAMES, define
 # HAVE_RAW_DECL_name if the function has a declaration among INCLUDES
 # even after being undefined as a macro.
@@ -23,25 +25,38 @@ dnl with or without modifications, as long as this notice is preserved.
 # needing gl_WARN_ON_USE_PREPARE.
 AC_DEFUN([gl_WARN_ON_USE_PREPARE],
 [
-  m4_foreach_w([gl_decl], [$2],
-    [AH_TEMPLATE([HAVE_RAW_DECL_]AS_TR_CPP(m4_defn([gl_decl])),
-      [Define to 1 if ]m4_defn([gl_decl])[ is declared even after
-       undefining macros.])])dnl
-dnl FIXME: gl_Symbol must be used unquoted until we can assume
-dnl autoconf 2.64 or newer.
-  for gl_func in m4_flatten([$2]); do
-    AS_VAR_PUSHDEF([gl_Symbol], [gl_cv_have_raw_decl_$gl_func])dnl
-    AC_CACHE_CHECK([whether $gl_func is declared without a macro],
-      gl_Symbol,
-      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([$1],
-[@%:@undef $gl_func
-  (void) $gl_func;])],
-        [AS_VAR_SET(gl_Symbol, [yes])], [AS_VAR_SET(gl_Symbol, [no])])])
-    AS_VAR_IF(gl_Symbol, [yes],
-      [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_RAW_DECL_$gl_func]), [1])
-       dnl shortcut - if the raw declaration exists, then set a cache
-       dnl variable to allow skipping any later AC_CHECK_DECL efforts
-       eval ac_cv_have_decl_$gl_func=yes])
-    AS_VAR_POPDEF([gl_Symbol])dnl
-  done
+  m4_ifdef([gl_POSIXCHECK],
+    [m4_foreach_w([gl_decl], [$2],
+       [AH_TEMPLATE([HAVE_RAW_DECL_]AS_TR_CPP(m4_defn([gl_decl])),
+         [Define to 1 if ]m4_defn([gl_decl])[ is declared even after
+          undefining macros.])])dnl
+     for gl_func in m4_flatten([$2]); do
+       AS_VAR_PUSHDEF([gl_Symbol], [gl_cv_have_raw_decl_$gl_func])dnl
+       dnl As a workaround to implicit built-in function declarations in
+       dnl clang (e.g. strndup), reference ac_compile_for_check_decl instead
+       dnl of ac_compile.  If, for whatever reason, the override of AC_PROG_CC
+       dnl in zzgnulib.m4 is inactive, use the original ac_compile.
+       ac_save_ac_compile="$ac_compile"
+       if test -n "$ac_compile_for_check_decl"; then
+         ac_compile="$ac_compile_for_check_decl"
+       fi
+       AC_CACHE_CHECK([whether $gl_func is declared without a macro],
+         [gl_Symbol],
+         [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([$1],
+[[#undef $gl_func
+  (void) $gl_func;]])],
+           [AS_VAR_SET([gl_Symbol], [yes])], [AS_VAR_SET([gl_Symbol], [no])])])
+       ac_compile="$ac_save_ac_compile"
+       AS_VAR_IF([gl_Symbol], [yes],
+         [AC_DEFINE_UNQUOTED(AS_TR_CPP([HAVE_RAW_DECL_$gl_func]), [1])
+          dnl Shortcut for an AC_CHECK_DECL invocation that may come later:
+          dnl If the raw declaration exists with the given includes, then
+          dnl AC_CHECK_DECL with its many includes would see it as well.
+          dnl So, set a cache variable to allow skipping any later
+          dnl AC_CHECK_DECL invocation for $gl_func.
+          eval "ac_cv_have_decl_$gl_func=yes"
+         ])
+       AS_VAR_POPDEF([gl_Symbol])dnl
+     done
+    ])
 ])