1 files changed, 98 insertions, 0 deletions
diff --git a/gl/m4/setlocale_null.m4 b/gl/m4/setlocale_null.m4
new file mode 100644
index 0000000..09ea50e
--- /dev/null
+++ b/gl/m4/setlocale_null.m4
@@ -0,0 +1,98 @@
+# setlocale_null.m4 serial 5
+dnl Copyright (C) 2019-2022 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.
+
+AC_DEFUN([gl_FUNC_SETLOCALE_NULL],
+[
+  AC_REQUIRE([AC_CANONICAL_HOST])
+  AC_REQUIRE([gl_PTHREADLIB])
+  AC_CHECK_HEADERS_ONCE([threads.h])
+
+  AC_CACHE_CHECK([whether setlocale (LC_ALL, NULL) is multithread-safe],
+    [gl_cv_func_setlocale_null_all_mtsafe],
+    [case "$host_os" in
+       # Guess no on musl libc, macOS, FreeBSD, NetBSD, OpenBSD, AIX, Haiku, Cygwin.
+       *-musl* | darwin* | freebsd* | midnightbsd* | netbsd* | openbsd* | aix* | haiku* | cygwin*)
+         gl_cv_func_setlocale_null_all_mtsafe=no ;;
+       # Guess yes on glibc, HP-UX, IRIX, Solaris, native Windows.
+       *-gnu* | gnu* | hpux* | irix* | solaris* | mingw*)
+         gl_cv_func_setlocale_null_all_mtsafe=yes ;;
+       # If we don't know, obey --enable-cross-guesses.
+       *)
+         gl_cv_func_setlocale_null_all_mtsafe="$gl_cross_guess_normal" ;;
+     esac
+    ])
+  dnl On platforms without multithreading, there is no issue.
+  case "$host_os" in
+    mingw*) ;;
+    *)
+      if test $gl_pthread_api = no && test $ac_cv_header_threads_h = no; then
+        gl_cv_func_setlocale_null_all_mtsafe="trivially yes"
+      fi
+      ;;
+  esac
+  case "$gl_cv_func_setlocale_null_all_mtsafe" in
+    *yes) SETLOCALE_NULL_ALL_MTSAFE=1 ;;
+    *)    SETLOCALE_NULL_ALL_MTSAFE=0 ;;
+  esac
+  AC_DEFINE_UNQUOTED([SETLOCALE_NULL_ALL_MTSAFE], [$SETLOCALE_NULL_ALL_MTSAFE],
+    [Define to 1 if setlocale (LC_ALL, NULL) is multithread-safe.])
+
+  dnl This is about a single category (not LC_ALL).
+  AC_CACHE_CHECK([whether setlocale (category, NULL) is multithread-safe],
+    [gl_cv_func_setlocale_null_one_mtsafe],
+    [case "$host_os" in
+       # Guess no on OpenBSD, AIX.
+       openbsd* | aix*)
+         gl_cv_func_setlocale_null_one_mtsafe=no ;;
+       # Guess yes on glibc, musl libc, macOS, FreeBSD, NetBSD, HP-UX, IRIX, Solaris, Haiku, Cygwin, native Windows.
+       *-gnu* | gnu* | *-musl* | darwin* | freebsd* | midnightbsd* | netbsd* | hpux* | irix* | solaris* | haiku* | cygwin* | mingw*)
+         gl_cv_func_setlocale_null_one_mtsafe=yes ;;
+       # If we don't know, obey --enable-cross-guesses.
+       *)
+         gl_cv_func_setlocale_null_one_mtsafe="$gl_cross_guess_normal" ;;
+     esac
+    ])
+  dnl On platforms without multithreading, there is no issue.
+  case "$host_os" in
+    mingw*) ;;
+    *)
+      if test $gl_pthread_api = no && test $ac_cv_header_threads_h = no; then
+        gl_cv_func_setlocale_null_one_mtsafe="trivially yes"
+      fi
+      ;;
+  esac
+  case "$gl_cv_func_setlocale_null_one_mtsafe" in
+    *yes) SETLOCALE_NULL_ONE_MTSAFE=1 ;;
+    *)    SETLOCALE_NULL_ONE_MTSAFE=0 ;;
+  esac
+  AC_DEFINE_UNQUOTED([SETLOCALE_NULL_ONE_MTSAFE], [$SETLOCALE_NULL_ONE_MTSAFE],
+    [Define to 1 if setlocale (category, NULL) is multithread-safe.])
+
+  dnl Determine link dependencies of lib/setlocale_null.c and lib/setlocale-lock.c.
+  if test $SETLOCALE_NULL_ALL_MTSAFE = 0 || test $SETLOCALE_NULL_ONE_MTSAFE = 0; then
+    case "$host_os" in
+      mingw*) LIB_SETLOCALE_NULL= ;;
+      *)
+        gl_WEAK_SYMBOLS
+        case "$gl_cv_have_weak" in
+          *yes) LIB_SETLOCALE_NULL= ;;
+          *)    LIB_SETLOCALE_NULL="$LIBPTHREAD" ;;
+        esac
+        ;;
+    esac
+  else
+    LIB_SETLOCALE_NULL=
+  fi
+  dnl LIB_SETLOCALE_NULL is expected to be '-pthread' or '-lpthread' on AIX
+  dnl with gcc or xlc, and empty otherwise.
+  AC_SUBST([LIB_SETLOCALE_NULL])
+])
+
+# Prerequisites of lib/setlocale-lock.c.
+AC_DEFUN([gl_PREREQ_SETLOCALE_LOCK],
+[
+  gl_VISIBILITY
+])