tests: Fix internationalization problems on native Windows

[Bruno Haible]

In a testdir of the modules nstrftime and c-nstrftime, I see a test failure
of test-nstrftime-2.sh, in particular with this output:

Format as ISO 8601: 2017-10-26 06:40:03.123456789
%a directive: Thu
../../gltests/test-nstrftime.h:393: assertion 'STREQ (buf, "jeu.") || STREQ 
(buf, "Jeu")' failed

This shows that the internationalization is not working here. The cause
is that the setlocale() function here is not overridden by gnulib, and
the native Windows setlocale() function, when called with "" argument,
ignores the LC_ALL environment variable.

This patch fixes it.


2024-05-27  Bruno Haible  <bruno@clisp.org>

        tests: Fix internationalization problems on native Windows.
        * doc/posix-functions/setlocale.texi: Clarify the deficiency of
        setlocale() on native Windows.
        * modules/c-nstrftime-tests (Depends-on): Add setlocale.
        * modules/dfa-tests (Depends-on): Likewise.
        * modules/hard-locale-tests (Depends-on): Likewise.
        * modules/localcharset-tests (Depends-on): Likewise.
        * modules/nstrftime-tests (Depends-on): Likewise.

diff --git a/doc/posix-functions/setlocale.texi 
b/doc/posix-functions/setlocale.texi
index 6e232200f8..2798e224cb 100644
--- a/doc/posix-functions/setlocale.texi
+++ b/doc/posix-functions/setlocale.texi
@@ -9,9 +9,9 @@
 Portability problems fixed by Gnulib module @code{setlocale}:
 @itemize
 @item
-On Windows platforms (excluding Cygwin), @code{setlocale(@var{category},NULL)}
-ignores the environment variables @code{LC_ALL}, @code{@var{category}}, and
-@code{LANG}.
+On Windows platforms (excluding Cygwin), @code{setlocale(@var{category},"")}
+and @code{setlocale(@var{category},NULL)} both ignore the environment variables
+@code{LC_ALL}, @code{@var{category}}, and @code{LANG}.
 @item
 On Windows platforms (excluding Cygwin) and Cygwin 1.5.x,
 @code{setlocale(LC_ALL,@var{name})} succeeds and sets the LC_CTYPE category to
diff --git a/modules/c-nstrftime-tests b/modules/c-nstrftime-tests
index fda810d09b..82d0a43d54 100644
--- a/modules/c-nstrftime-tests
+++ b/modules/c-nstrftime-tests
@@ -11,6 +11,7 @@ Depends-on:
 atoll
 c99
 intprops
+setlocale
 strerror
 
 configure.ac:
diff --git a/modules/dfa-tests b/modules/dfa-tests
index 53049cee4c..d27113168a 100644
--- a/modules/dfa-tests
+++ b/modules/dfa-tests
@@ -11,6 +11,7 @@ stdlib
 string
 unistd
 regex
+setlocale
 test-framework-sh
 
 configure.ac:
diff --git a/modules/hard-locale-tests b/modules/hard-locale-tests
index e4bc65a256..cac960621f 100644
--- a/modules/hard-locale-tests
+++ b/modules/hard-locale-tests
@@ -4,6 +4,7 @@ tests/locale.c
 m4/musl.m4
 
 Depends-on:
+setlocale
 
 configure.ac:
 gl_MUSL_LIBC
diff --git a/modules/localcharset-tests b/modules/localcharset-tests
index cb84f2cdc7..3f2dde6dfd 100644
--- a/modules/localcharset-tests
+++ b/modules/localcharset-tests
@@ -2,6 +2,7 @@ Files:
 tests/test-localcharset.c
 
 Depends-on:
+setlocale
 
 configure.ac:
 
diff --git a/modules/nstrftime-tests b/modules/nstrftime-tests
index 24212a4f84..b5c6ac2fa5 100644
--- a/modules/nstrftime-tests
+++ b/modules/nstrftime-tests
@@ -12,6 +12,7 @@ Depends-on:
 atoll
 c99
 intprops
+setlocale
 strerror
 
 configure.ac: