setlocale: Make calls with NULL argument multithread-safe.

* lib/setlocale.c: Include <errno.h>.
(setlocale_mtsafe): New function.
(setlocale_unixlike): Invoke setlocale_mtsafe instead of setlocale.
(setlocale_improved): Renamed from rpl_setlocale.
* m4/setlocale.m4 (gl_FUNC_SETLOCALE): Require gl_FUNC_SETLOCALE_NULL.
Set and define NEED_SETLOCALE_IMPROVED and NEED_SETLOCALE_MTSAFE. Set
LIB_SETLOCALE.
* modules/setlocale (Depends-on): Add setlocale-null. Update conditions.
(Link): New section.
* tests/locale.c: Undefine setlocale.
* tests/test-setlocale_null-one.c: Likewise.
* tests/test-setlocale_null-all.c: Likewise.
* modules/setlocale-tests (Makefile.am): Link the test programs with
$(LIB_SETLOCALE).
* modules/astrxfrm-tests (Makefile.am): Likewise.
* modules/btowc-tests (Makefile.am): Likewise.
* modules/c-ctype-tests (Makefile.am): Likewise.
* modules/c-snprintf-tests (Makefile.am): Likewise.
* modules/c-strcase-tests (Makefile.am): Likewise.
* modules/c-vasprintf-tests (Makefile.am): Likewise.
* modules/c-vsnprintf-tests (Makefile.am): Likewise.
* modules/c-xvasprintf-tests (Makefile.am): Likewise.
* modules/dfa-tests (Makefile.am): Likewise.
* modules/duplocale-tests (Makefile.am): Likewise.
* modules/hard-locale-tests (Makefile.am): Likewise.
* modules/localcharset-tests (Makefile.am): Likewise.
* modules/localename-tests (Makefile.am): Likewise.
* modules/mbmemcasecmp-tests (Makefile.am): Likewise.
* modules/mbmemcasecoll-tests (Makefile.am): Likewise.
* modules/mbrtowc-tests (Makefile.am): Likewise.
* modules/mbscasecmp-tests (Makefile.am): Likewise.
* modules/mbscasestr-tests (Makefile.am): Likewise.
* modules/mbschr-tests (Makefile.am): Likewise.
* modules/mbscspn-tests (Makefile.am): Likewise.
* modules/mbsinit-tests (Makefile.am): Likewise.
* modules/mbsncasecmp-tests (Makefile.am): Likewise.
* modules/mbsnrtowcs-tests (Makefile.am): Likewise.
* modules/mbspbrk-tests (Makefile.am): Likewise.
* modules/mbspcasecmp-tests (Makefile.am): Likewise.
* modules/mbsrchr-tests (Makefile.am): Likewise.
* modules/mbsrtowcs-tests (Makefile.am): Likewise.
* modules/mbsspn-tests (Makefile.am): Likewise.
* modules/mbsstr-tests (Makefile.am): Likewise.
* modules/nl_langinfo-tests (Makefile.am): Likewise.
* modules/quotearg-tests (Makefile.am): Likewise.
* modules/regex-tests (Makefile.am): Likewise.
* modules/strfmon_l-tests (Makefile.am): Likewise.
* modules/strtod-tests (Makefile.am): Likewise.
* modules/strtold-tests (Makefile.am): Likewise.
* modules/unicase/locale-language-tests (Makefile.am): Likewise.
* modules/unicase/ulc-casecmp-tests (Makefile.am): Likewise.
* modules/unicase/ulc-casecoll-tests (Makefile.am): Likewise.
* modules/unigbrk/ulc-grapheme-breaks-tests (Makefile.am): Likewise.
* modules/unistdio/u8-vasnprintf-tests (Makefile.am): Likewise.
* modules/unistdio/u16-vasnprintf-tests (Makefile.am): Likewise.
* modules/unistdio/u32-vasnprintf-tests (Makefile.am): Likewise.
* modules/unistdio/ulc-vasnprintf-tests (Makefile.am): Likewise.
* modules/uniwbrk/ulc-wordbreaks-tests (Makefile.am): Likewise.
* modules/vasnprintf-posix-tests (Makefile.am): Likewise.
* modules/wcrtomb-tests (Makefile.am): Likewise.
* modules/wcsnrtombs-tests (Makefile.am): Likewise.
* modules/wcsrtombs-tests (Makefile.am): Likewise.
* modules/wcwidth-tests (Makefile.am): Likewise.
* doc/posix-functions/setlocale.texi: Mention that the multithread-
safety fix is also available in module 'setlocale'.

51 files changed, 69 insertions, 50 deletions

diff --git a/modules/astrxfrm-tests b/modules/astrxfrm-tests
index af8c1003ed..b113e34a31 100644
--- a/modules/astrxfrm-tests
+++ b/modules/astrxfrm-tests
@@ -9,3 +9,4 @@ configure.ac:
 Makefile.am:
 TESTS += test-astrxfrm
 check_PROGRAMS += test-astrxfrm
+test_astrxfrm_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/btowc-tests b/modules/btowc-tests
index 66196b1332..e36cc61c42 100644
--- a/modules/btowc-tests
+++ b/modules/btowc-tests
@@ -18,4 +18,4 @@ Makefile.am:
 TESTS += test-btowc1.sh test-btowc2.sh
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@' LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-btowc
-
+test_btowc_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/c-ctype-tests b/modules/c-ctype-tests
index e66a4cca87..02706b00de 100644
--- a/modules/c-ctype-tests
+++ b/modules/c-ctype-tests
@@ -11,3 +11,4 @@ configure.ac:
 Makefile.am:
 TESTS += test-c-ctype
 check_PROGRAMS += test-c-ctype
+test_c_ctype_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/c-snprintf-tests b/modules/c-snprintf-tests
index 86d6a1420c..231a4fdb66 100644
--- a/modules/c-snprintf-tests
+++ b/modules/c-snprintf-tests
@@ -13,5 +13,6 @@ gt_LOCALE_FR
 
 Makefile.am:
 TESTS += test-c-snprintf.sh
-check_PROGRAMS += test-c-snprintf
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@'
+check_PROGRAMS += test-c-snprintf
+test_c_snprintf_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/c-strcase-tests b/modules/c-strcase-tests
index 5802f41eb1..7cdb29cef2 100644
--- a/modules/c-strcase-tests
+++ b/modules/c-strcase-tests
@@ -19,3 +19,5 @@ Makefile.am:
 TESTS += test-c-strcase.sh
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@' LOCALE_TR_UTF8='@LOCALE_TR_UTF8@'
 check_PROGRAMS += test-c-strcasecmp test-c-strncasecmp
+test_c_strcasecmp_LDADD = $(LDADD) $(LIB_SETLOCALE)
+test_c_strncasecmp_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/c-vasprintf-tests b/modules/c-vasprintf-tests
index 940956366c..b82fc8b7e1 100644
--- a/modules/c-vasprintf-tests
+++ b/modules/c-vasprintf-tests
@@ -13,5 +13,6 @@ gt_LOCALE_FR
 
 Makefile.am:
 TESTS += test-c-vasprintf.sh
-check_PROGRAMS += test-c-vasprintf
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@'
+check_PROGRAMS += test-c-vasprintf
+test_c_vasprintf_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/c-vsnprintf-tests b/modules/c-vsnprintf-tests
index 6a76092ddd..542d8d98f3 100644
--- a/modules/c-vsnprintf-tests
+++ b/modules/c-vsnprintf-tests
@@ -13,5 +13,6 @@ gt_LOCALE_FR
 
 Makefile.am:
 TESTS += test-c-vsnprintf.sh
-check_PROGRAMS += test-c-vsnprintf
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@'
+check_PROGRAMS += test-c-vsnprintf
+test_c_vsnprintf_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/c-xvasprintf-tests b/modules/c-xvasprintf-tests
index a118de0a67..75ce919410 100644
--- a/modules/c-xvasprintf-tests
+++ b/modules/c-xvasprintf-tests
@@ -14,6 +14,6 @@ gt_LOCALE_FR
 
 Makefile.am:
 TESTS += test-c-xvasprintf.sh
-check_PROGRAMS += test-c-xvasprintf
-test_c_xvasprintf_LDADD = $(LDADD) @LIBINTL@
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@'
+check_PROGRAMS += test-c-xvasprintf
+test_c_xvasprintf_LDADD = $(LDADD) $(LIB_SETLOCALE) @LIBINTL@
diff --git a/modules/dfa-tests b/modules/dfa-tests
index ee4354a268..0128dca2b0 100644
--- a/modules/dfa-tests
+++ b/modules/dfa-tests
@@ -18,4 +18,4 @@ TESTS +=			\
   dfa-match.sh
 
 check_PROGRAMS += dfa-match-aux
-dfa_match_aux_LDADD = $(LDADD) @LIBINTL@ $(LIBTHREAD)
+dfa_match_aux_LDADD = $(LDADD) $(LIB_SETLOCALE) @LIBINTL@ $(LIBTHREAD)
diff --git a/modules/duplocale-tests b/modules/duplocale-tests
index 6545c4e33a..e30810982a 100644
--- a/modules/duplocale-tests
+++ b/modules/duplocale-tests
@@ -15,4 +15,4 @@ gt_FUNC_USELOCALE
 Makefile.am:
 TESTS += test-duplocale
 check_PROGRAMS += test-duplocale
-test_duplocale_LDADD = $(LDADD) @LIB_DUPLOCALE@
+test_duplocale_LDADD = $(LDADD) $(LIB_SETLOCALE) @LIB_DUPLOCALE@
diff --git a/modules/hard-locale-tests b/modules/hard-locale-tests
index a501781d8d..ddd101f175 100644
--- a/modules/hard-locale-tests
+++ b/modules/hard-locale-tests
@@ -16,4 +16,4 @@ Makefile.am:
 TESTS += test-hard-locale
 check_PROGRAMS += test-hard-locale
 noinst_PROGRAMS += locale
-test_hard_locale_LDADD = $(LDADD) @LIB_HARD_LOCALE@
+test_hard_locale_LDADD = $(LDADD) $(LIB_SETLOCALE) @LIB_HARD_LOCALE@
diff --git a/modules/localcharset-tests b/modules/localcharset-tests
index 52e4c60d59..70d5cfd551 100644
--- a/modules/localcharset-tests
+++ b/modules/localcharset-tests
@@ -7,3 +7,4 @@ configure.ac:
 
 Makefile.am:
 noinst_PROGRAMS += test-localcharset
+test_localcharset_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/localename-tests b/modules/localename-tests
index 4940965d03..4b9a28a65c 100644
--- a/modules/localename-tests
+++ b/modules/localename-tests
@@ -15,5 +15,5 @@ AC_CHECK_FUNCS_ONCE([newlocale])
 Makefile.am:
 TESTS += test-localename
 check_PROGRAMS += test-localename
-test_localename_LDADD = $(LDADD) @INTL_MACOSX_LIBS@ $(LIBTHREAD)
+test_localename_LDADD = $(LDADD) $(LIB_SETLOCALE) @INTL_MACOSX_LIBS@ $(LIBTHREAD)
 
diff --git a/modules/mbmemcasecmp-tests b/modules/mbmemcasecmp-tests
index 29c8cf68fe..16a11231c2 100644
--- a/modules/mbmemcasecmp-tests
+++ b/modules/mbmemcasecmp-tests
@@ -25,4 +25,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_FR_UTF8='@LOCALE_FR_UTF8@' \
   LOCALE_TR_UTF8='@LOCALE_TR_UTF8@'
 check_PROGRAMS += test-mbmemcasecmp
-test_mbmemcasecmp_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbmemcasecmp_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbmemcasecoll-tests b/modules/mbmemcasecoll-tests
index fb308d993d..56a3db0af2 100644
--- a/modules/mbmemcasecoll-tests
+++ b/modules/mbmemcasecoll-tests
@@ -25,4 +25,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_FR_UTF8='@LOCALE_FR_UTF8@' \
   LOCALE_TR_UTF8='@LOCALE_TR_UTF8@'
 check_PROGRAMS += test-mbmemcasecoll
-test_mbmemcasecoll_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbmemcasecoll_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbrtowc-tests b/modules/mbrtowc-tests
index a2839cbd72..86008d867d 100644
--- a/modules/mbrtowc-tests
+++ b/modules/mbrtowc-tests
@@ -41,4 +41,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbrtowc test-mbrtowc-w32
-test_mbrtowc_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbrtowc_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbscasecmp-tests b/modules/mbscasecmp-tests
index 8548050dd6..9f77064c3b 100644
--- a/modules/mbscasecmp-tests
+++ b/modules/mbscasecmp-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbscasecmp.sh
 TESTS_ENVIRONMENT += LOCALE_TR_UTF8='@LOCALE_TR_UTF8@'
 check_PROGRAMS += test-mbscasecmp
-test_mbscasecmp_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbscasecmp_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbscasestr-tests b/modules/mbscasestr-tests
index bc2df73cc7..3395c1fd8c 100644
--- a/modules/mbscasestr-tests
+++ b/modules/mbscasestr-tests
@@ -25,6 +25,6 @@ TESTS += test-mbscasestr1 test-mbscasestr2.sh test-mbscasestr3.sh test-mbscasest
 TESTS_ENVIRONMENT += LOCALE_FR_UTF8='@LOCALE_FR_UTF8@' LOCALE_TR_UTF8='@LOCALE_TR_UTF8@' LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbscasestr1 test-mbscasestr2 test-mbscasestr3 test-mbscasestr4
 test_mbscasestr1_LDADD = $(LDADD) $(LIBTHREAD)
-test_mbscasestr2_LDADD = $(LDADD) $(LIBTHREAD)
-test_mbscasestr3_LDADD = $(LDADD) $(LIBTHREAD)
-test_mbscasestr4_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbscasestr2_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
+test_mbscasestr3_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
+test_mbscasestr4_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbschr-tests b/modules/mbschr-tests
index f04e03c5d4..33ee83fdcf 100644
--- a/modules/mbschr-tests
+++ b/modules/mbschr-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbschr.sh
 TESTS_ENVIRONMENT += LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbschr
-test_mbschr_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbschr_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbscspn-tests b/modules/mbscspn-tests
index a6eada177b..8c4a3d154d 100644
--- a/modules/mbscspn-tests
+++ b/modules/mbscspn-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbscspn.sh
 TESTS_ENVIRONMENT += LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-mbscspn
-test_mbscspn_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbscspn_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsinit-tests b/modules/mbsinit-tests
index e509efed3f..0674e9c610 100644
--- a/modules/mbsinit-tests
+++ b/modules/mbsinit-tests
@@ -17,4 +17,4 @@ Makefile.am:
 TESTS += test-mbsinit.sh
 TESTS_ENVIRONMENT += LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-mbsinit
-test_mbsinit_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsinit_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsncasecmp-tests b/modules/mbsncasecmp-tests
index ad04325bd9..050201a5c2 100644
--- a/modules/mbsncasecmp-tests
+++ b/modules/mbsncasecmp-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbsncasecmp.sh
 TESTS_ENVIRONMENT += LOCALE_TR_UTF8='@LOCALE_TR_UTF8@'
 check_PROGRAMS += test-mbsncasecmp
-test_mbsncasecmp_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsncasecmp_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsnrtowcs-tests b/modules/mbsnrtowcs-tests
index ac67c854bb..4d90f17a81 100644
--- a/modules/mbsnrtowcs-tests
+++ b/modules/mbsnrtowcs-tests
@@ -31,4 +31,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbsnrtowcs
-test_mbsnrtowcs_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsnrtowcs_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbspbrk-tests b/modules/mbspbrk-tests
index 587ff5dcc3..902e5b39c5 100644
--- a/modules/mbspbrk-tests
+++ b/modules/mbspbrk-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbspbrk.sh
 TESTS_ENVIRONMENT += LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-mbspbrk
-test_mbspbrk_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbspbrk_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbspcasecmp-tests b/modules/mbspcasecmp-tests
index e1b87c36a2..e6f11ffa4d 100644
--- a/modules/mbspcasecmp-tests
+++ b/modules/mbspcasecmp-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbspcasecmp.sh
 TESTS_ENVIRONMENT += LOCALE_TR_UTF8='@LOCALE_TR_UTF8@'
 check_PROGRAMS += test-mbspcasecmp
-test_mbspcasecmp_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbspcasecmp_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsrchr-tests b/modules/mbsrchr-tests
index 326d566d6f..1d9780426d 100644
--- a/modules/mbsrchr-tests
+++ b/modules/mbsrchr-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbsrchr.sh
 TESTS_ENVIRONMENT += LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbsrchr
-test_mbsrchr_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsrchr_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsrtowcs-tests b/modules/mbsrtowcs-tests
index 24dfa3f78b..3de9d73f61 100644
--- a/modules/mbsrtowcs-tests
+++ b/modules/mbsrtowcs-tests
@@ -31,4 +31,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbsrtowcs
-test_mbsrtowcs_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsrtowcs_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsspn-tests b/modules/mbsspn-tests
index 8a5fe23396..994a7062e6 100644
--- a/modules/mbsspn-tests
+++ b/modules/mbsspn-tests
@@ -15,4 +15,4 @@ Makefile.am:
 TESTS += test-mbsspn.sh
 TESTS_ENVIRONMENT += LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-mbsspn
-test_mbsspn_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsspn_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/mbsstr-tests b/modules/mbsstr-tests
index a0a878b1f0..739e51deec 100644
--- a/modules/mbsstr-tests
+++ b/modules/mbsstr-tests
@@ -21,5 +21,5 @@ TESTS += test-mbsstr1 test-mbsstr2.sh test-mbsstr3.sh
 TESTS_ENVIRONMENT += LOCALE_FR_UTF8='@LOCALE_FR_UTF8@' LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-mbsstr1 test-mbsstr2 test-mbsstr3
 test_mbsstr1_LDADD = $(LDADD) $(LIBTHREAD)
-test_mbsstr2_LDADD = $(LDADD) $(LIBTHREAD)
-test_mbsstr3_LDADD = $(LDADD) $(LIBTHREAD)
+test_mbsstr2_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
+test_mbsstr3_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBTHREAD)
diff --git a/modules/nl_langinfo-tests b/modules/nl_langinfo-tests
index db0a57d1de..9474bbd86f 100644
--- a/modules/nl_langinfo-tests
+++ b/modules/nl_langinfo-tests
@@ -20,4 +20,4 @@ Makefile.am:
 TESTS += test-nl_langinfo.sh test-nl_langinfo-mt
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@' LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-nl_langinfo test-nl_langinfo-mt
-test_nl_langinfo_mt_LDADD = $(LDADD) $(LIBMULTITHREAD) $(LIB_NANOSLEEP)
+test_nl_langinfo_mt_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBMULTITHREAD) $(LIB_NANOSLEEP)
diff --git a/modules/quotearg-tests b/modules/quotearg-tests
index 61aa27ce74..486956affc 100644
--- a/modules/quotearg-tests
+++ b/modules/quotearg-tests
@@ -27,4 +27,4 @@ Makefile.am:
 TESTS += test-quotearg.sh
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@' LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-quotearg
-test_quotearg_LDADD = $(LDADD) @LIBINTL@ $(LIBTHREAD)
+test_quotearg_LDADD = $(LDADD) $(LIB_SETLOCALE) @LIBINTL@ $(LIBTHREAD)
diff --git a/modules/regex-tests b/modules/regex-tests
index 0782303655..e8821ec52d 100644
--- a/modules/regex-tests
+++ b/modules/regex-tests
@@ -11,4 +11,4 @@ configure.ac:
 Makefile.am:
 TESTS += test-regex
 check_PROGRAMS += test-regex
-test_regex_LDADD = $(LDADD) @LIBINTL@ $(LIBTHREAD)
+test_regex_LDADD = $(LDADD) $(LIB_SETLOCALE) @LIBINTL@ $(LIBTHREAD)
diff --git a/modules/setlocale b/modules/setlocale
index 5d5ed81dca..cc92e1a8bc 100644
--- a/modules/setlocale
+++ b/modules/setlocale
@@ -7,7 +7,8 @@ m4/setlocale.m4
 
 Depends-on:
 locale
-localename      [test $REPLACE_SETLOCALE = 1]
+localename      [test $NEED_SETLOCALE_IMPROVED = 1]
+setlocale-null  [test $NEED_SETLOCALE_MTSAFE = 1]
 
 configure.ac:
 gl_FUNC_SETLOCALE
@@ -22,6 +23,9 @@ Makefile.am:
 Include:
 <locale.h>
 
+Link:
+$(LIB_SETLOCALE)
+
 License:
 LGPL
 
diff --git a/modules/setlocale-tests b/modules/setlocale-tests
index 8c35c9d82c..25129f92ef 100644
--- a/modules/setlocale-tests
+++ b/modules/setlocale-tests
@@ -27,3 +27,5 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-setlocale1 test-setlocale2
+test_setlocale1_LDADD = $(LDADD) @LIB_SETLOCALE@
+test_setlocale2_LDADD = $(LDADD) @LIB_SETLOCALE@
diff --git a/modules/strfmon_l-tests b/modules/strfmon_l-tests
index 871962c6f9..cf2d6a2fa3 100644
--- a/modules/strfmon_l-tests
+++ b/modules/strfmon_l-tests
@@ -10,3 +10,4 @@ configure.ac:
 Makefile.am:
 TESTS += test-strfmon_l
 check_PROGRAMS += test-strfmon_l
+test_strfmon_l_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/strtod-tests b/modules/strtod-tests
index e3cd57f66e..03966580f9 100644
--- a/modules/strtod-tests
+++ b/modules/strtod-tests
@@ -26,3 +26,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_FR='@LOCALE_FR@' \
   LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-strtod1
+test_strtod1_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/strtold-tests b/modules/strtold-tests
index c58e52c2ab..dc82f50a08 100644
--- a/modules/strtold-tests
+++ b/modules/strtold-tests
@@ -26,3 +26,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_FR='@LOCALE_FR@' \
   LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-strtold1
+test_strtold1_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/unicase/locale-language-tests b/modules/unicase/locale-language-tests
index 2cf5926963..1399e52692 100644
--- a/modules/unicase/locale-language-tests
+++ b/modules/unicase/locale-language-tests
@@ -23,4 +23,4 @@ TESTS += unicase/test-locale-language.sh
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@' LOCALE_FR_UTF8='@LOCALE_FR_UTF8@' LOCALE_JA='@LOCALE_JA@' LOCALE_TR_UTF8='@LOCALE_TR_UTF8@' LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-locale-language
 test_locale_language_SOURCES = unicase/test-locale-language.c
-test_locale_language_LDADD = $(LDADD) $(LIBUNISTRING) @INTL_MACOSX_LIBS@ $(LIBTHREAD)
+test_locale_language_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @INTL_MACOSX_LIBS@ $(LIBTHREAD)
diff --git a/modules/unicase/ulc-casecmp-tests b/modules/unicase/ulc-casecmp-tests
index 0d78fbe256..08a8620d5f 100644
--- a/modules/unicase/ulc-casecmp-tests
+++ b/modules/unicase/ulc-casecmp-tests
@@ -22,5 +22,5 @@ TESTS_ENVIRONMENT += \
   LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-ulc-casecmp
 test_ulc_casecmp_SOURCES = unicase/test-ulc-casecmp.c
-test_ulc_casecmp_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_ulc_casecmp_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
 
diff --git a/modules/unicase/ulc-casecoll-tests b/modules/unicase/ulc-casecoll-tests
index bd2e59b82d..1610872651 100644
--- a/modules/unicase/ulc-casecoll-tests
+++ b/modules/unicase/ulc-casecoll-tests
@@ -22,5 +22,5 @@ TESTS_ENVIRONMENT += \
   LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-ulc-casecoll
 test_ulc_casecoll_SOURCES = unicase/test-ulc-casecoll.c
-test_ulc_casecoll_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_ulc_casecoll_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
 
diff --git a/modules/unigbrk/ulc-grapheme-breaks-tests b/modules/unigbrk/ulc-grapheme-breaks-tests
index 187e26f05b..a6dacd0001 100644
--- a/modules/unigbrk/ulc-grapheme-breaks-tests
+++ b/modules/unigbrk/ulc-grapheme-breaks-tests
@@ -16,4 +16,4 @@ TESTS += unigbrk/test-ulc-grapheme-breaks.sh
 TESTS_ENVIRONMENT += LOCALE_AR='@LOCALE_AR@'
 check_PROGRAMS += test-ulc-grapheme-breaks
 test_ulc_grapheme_breaks_SOURCES = unigbrk/test-ulc-grapheme-breaks.c
-test_ulc_grapheme_breaks_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_ulc_grapheme_breaks_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
diff --git a/modules/unistdio/u16-vasnprintf-tests b/modules/unistdio/u16-vasnprintf-tests
index 3dc3cb0083..45e3ab2200 100644
--- a/modules/unistdio/u16-vasnprintf-tests
+++ b/modules/unistdio/u16-vasnprintf-tests
@@ -28,6 +28,6 @@ check_PROGRAMS += test-u16-vasnprintf1 test-u16-vasnprintf2 test-u16-vasnprintf3
 test_u16_vasnprintf1_SOURCES = unistdio/test-u16-vasnprintf1.c
 test_u16_vasnprintf1_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
 test_u16_vasnprintf2_SOURCES = unistdio/test-u16-vasnprintf2.c
-test_u16_vasnprintf2_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_u16_vasnprintf2_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
 test_u16_vasnprintf3_SOURCES = unistdio/test-u16-vasnprintf3.c
-test_u16_vasnprintf3_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_u16_vasnprintf3_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
diff --git a/modules/unistdio/u32-vasnprintf-tests b/modules/unistdio/u32-vasnprintf-tests
index 555319b4a1..7343c328e6 100644
--- a/modules/unistdio/u32-vasnprintf-tests
+++ b/modules/unistdio/u32-vasnprintf-tests
@@ -28,6 +28,6 @@ check_PROGRAMS += test-u32-vasnprintf1 test-u32-vasnprintf2 test-u32-vasnprintf3
 test_u32_vasnprintf1_SOURCES = unistdio/test-u32-vasnprintf1.c
 test_u32_vasnprintf1_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
 test_u32_vasnprintf2_SOURCES = unistdio/test-u32-vasnprintf2.c
-test_u32_vasnprintf2_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_u32_vasnprintf2_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
 test_u32_vasnprintf3_SOURCES = unistdio/test-u32-vasnprintf3.c
-test_u32_vasnprintf3_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_u32_vasnprintf3_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
diff --git a/modules/unistdio/u8-vasnprintf-tests b/modules/unistdio/u8-vasnprintf-tests
index 8d5e29512d..70c9820326 100644
--- a/modules/unistdio/u8-vasnprintf-tests
+++ b/modules/unistdio/u8-vasnprintf-tests
@@ -28,6 +28,6 @@ check_PROGRAMS += test-u8-vasnprintf1 test-u8-vasnprintf2 test-u8-vasnprintf3
 test_u8_vasnprintf1_SOURCES = unistdio/test-u8-vasnprintf1.c
 test_u8_vasnprintf1_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
 test_u8_vasnprintf2_SOURCES = unistdio/test-u8-vasnprintf2.c
-test_u8_vasnprintf2_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_u8_vasnprintf2_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
 test_u8_vasnprintf3_SOURCES = unistdio/test-u8-vasnprintf3.c
-test_u8_vasnprintf3_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_u8_vasnprintf3_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
diff --git a/modules/unistdio/ulc-vasnprintf-tests b/modules/unistdio/ulc-vasnprintf-tests
index b72c1888a7..0af236161d 100644
--- a/modules/unistdio/ulc-vasnprintf-tests
+++ b/modules/unistdio/ulc-vasnprintf-tests
@@ -24,6 +24,6 @@ check_PROGRAMS += test-ulc-vasnprintf1 test-ulc-vasnprintf2 test-ulc-vasnprintf3
 test_ulc_vasnprintf1_SOURCES = unistdio/test-ulc-vasnprintf1.c
 test_ulc_vasnprintf1_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@ $(LIBTHREAD)
 test_ulc_vasnprintf2_SOURCES = unistdio/test-ulc-vasnprintf2.c
-test_ulc_vasnprintf2_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@ $(LIBTHREAD)
+test_ulc_vasnprintf2_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@ $(LIBTHREAD)
 test_ulc_vasnprintf3_SOURCES = unistdio/test-ulc-vasnprintf3.c
-test_ulc_vasnprintf3_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@ $(LIBTHREAD)
+test_ulc_vasnprintf3_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@ $(LIBTHREAD)
diff --git a/modules/uniwbrk/ulc-wordbreaks-tests b/modules/uniwbrk/ulc-wordbreaks-tests
index 19f1ee6811..cfb866b503 100644
--- a/modules/uniwbrk/ulc-wordbreaks-tests
+++ b/modules/uniwbrk/ulc-wordbreaks-tests
@@ -16,5 +16,5 @@ TESTS += uniwbrk/test-ulc-wordbreaks.sh
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@'
 check_PROGRAMS += test-ulc-wordbreaks
 test_ulc_wordbreaks_SOURCES = uniwbrk/test-ulc-wordbreaks.c
-test_ulc_wordbreaks_LDADD = $(LDADD) $(LIBUNISTRING) @LIBICONV@
+test_ulc_wordbreaks_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING) @LIBICONV@
 
diff --git a/modules/vasnprintf-posix-tests b/modules/vasnprintf-posix-tests
index 6ba745bf14..2ea2791ddf 100644
--- a/modules/vasnprintf-posix-tests
+++ b/modules/vasnprintf-posix-tests
@@ -24,3 +24,5 @@ Makefile.am:
 TESTS += test-vasnprintf-posix test-vasnprintf-posix2.sh test-vasnprintf-posix3
 TESTS_ENVIRONMENT += LOCALE_FR='@LOCALE_FR@' LOCALE_FR_UTF8='@LOCALE_FR_UTF8@'
 check_PROGRAMS += test-vasnprintf-posix test-vasnprintf-posix2 test-vasnprintf-posix3
+test_vasnprintf_posix2_LDADD = $(LDADD) $(LIB_SETLOCALE)
+test_vasnprintf_posix3_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/wcrtomb-tests b/modules/wcrtomb-tests
index 32f9d3a7f0..43c28e8d53 100644
--- a/modules/wcrtomb-tests
+++ b/modules/wcrtomb-tests
@@ -35,4 +35,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-wcrtomb test-wcrtomb-w32
-
+test_wcrtomb_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/wcsnrtombs-tests b/modules/wcsnrtombs-tests
index 877dd17584..adeda4e9d1 100644
--- a/modules/wcsnrtombs-tests
+++ b/modules/wcsnrtombs-tests
@@ -28,4 +28,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-wcsnrtombs
-
+test_wcsnrtombs_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/wcsrtombs-tests b/modules/wcsrtombs-tests
index 4b6bf54172..2f52f68b20 100644
--- a/modules/wcsrtombs-tests
+++ b/modules/wcsrtombs-tests
@@ -28,4 +28,4 @@ TESTS_ENVIRONMENT += \
   LOCALE_JA='@LOCALE_JA@' \
   LOCALE_ZH_CN='@LOCALE_ZH_CN@'
 check_PROGRAMS += test-wcsrtombs
-
+test_wcsrtombs_LDADD = $(LDADD) $(LIB_SETLOCALE)
diff --git a/modules/wcwidth-tests b/modules/wcwidth-tests
index 9606674b90..875d18f8d3 100644
--- a/modules/wcwidth-tests
+++ b/modules/wcwidth-tests
@@ -12,4 +12,4 @@ configure.ac:
 Makefile.am:
 TESTS += test-wcwidth
 check_PROGRAMS += test-wcwidth
-test_wcwidth_LDADD = $(LDADD) $(LIBUNISTRING)
+test_wcwidth_LDADD = $(LDADD) $(LIB_SETLOCALE) $(LIBUNISTRING)