mbfile tests: Avoid test failure on mingw

[Bruno Haible]

On mingw, I see this test failure:

FAIL: test-mbfile.sh
====================

../../gltests/test-mbfile.c:49: assertion 'mb_len (next) == 2' failed
Stack trace:
0xbd502c13 main
        ../../gltests/test-mbfile.c:49

The cause is that setlocale has not installed an UTF-8 locale, but
a CP1252 locale. This patch avoids the failure, like in some other tests.


2024-05-29  Bruno Haible  <br...@clisp.org>

        mbfile tests: Avoid test failure on mingw.
        * tests/test-mbfile.c: Include <string.h>, localcharset.h.
        (main): Verify that setlocale() has installed an UTF-8 locale.
        * modules/mbfile-tests (Depends-on): Add localcharset.

diff --git a/modules/mbfile-tests b/modules/mbfile-tests
index 246702fc04..d52b9d4975 100644
--- a/modules/mbfile-tests
+++ b/modules/mbfile-tests
@@ -4,6 +4,7 @@ tests/test-mbfile.c
 tests/macros.h
 
 Depends-on:
+localcharset
 setlocale
 
 configure.ac:
diff --git a/tests/test-mbfile.c b/tests/test-mbfile.c
index 1d857a819b..3565404294 100644
--- a/tests/test-mbfile.c
+++ b/tests/test-mbfile.c
@@ -21,13 +21,20 @@
 #include "mbfile.h"
 
 #include <locale.h>
+#include <string.h>
 
+#include "localcharset.h"
 #include "macros.h"
 
 int
 main ()
 {
-  if (setlocale (LC_ALL, "en_US.UTF-8") == NULL)
+  /* Switch to an UTF-8 locale.  */
+  if (!(setlocale (LC_ALL, "en_US.UTF-8") != NULL
+        /* Check whether it's really an UTF-8 locale.
+           On native Windows, this setlocale call succeeds but the encoding
+           of this locale is CP1252, not UTF-8.  */
+        && strcmp (locale_charset (), "UTF-8") == 0))
     {
       fprintf (stderr, "Skipping test: English Unicode locale is not 
installed\n");
       return 77;