test: Fix and stabilize tst-wcsmbs-clone-overflow test

The test tst-wcsmbs-clone-overflow was initially added to tests-static.
However, this causes the test to be unstable because gconv modules
dynamically load libc.so. Any discrepancy between the statically linked
version and the dynamically loaded one can lead to a crash.

By removing the test from tests-static, it relies on dynamic linking,
safely bypassing the dlopen crash. Since the test is now dynamically
linked, it cannot use the internal thread-local symbol
_NL_CURRENT_DATA(LC_CTYPE) because _nl_current_LC_CTYPE is hidden in
libc.so, leading to undefined references. Thus, the test now uses
newlocale and uselocale, safely extracting the locale data from the
returned locale_t object.

Furthermore, using newlocale requires the gconv-modules configuration to
be built and available so that the ISO8859-1.so module can be
dynamically loaded. Otherwise, glibc falls back to the built-in C locale
conversions, leaving __shlib_handle as NULL and silently bypassing the
reference counter increment.
A new Makefile fragment, gen-gconv-modules.mk, is introduced to ensure
the gconv-modules are built before the test runs, and an explicit check
for __shlib_handle != NULL is added to the test.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

gen-gconv-modules.mk

@@ -0,0 +1,6 @@
+# defines target $(gen-gconv-modules) that ensures gconv-modules are available
+
+gen-gconv-modules := $(common-objpfx)iconvdata/gconv-modules
+
+$(gen-gconv-modules):
+	$(MAKE) -C ../iconvdata subdir=iconvdata $@

localedata/Makefile

@@ -287,7 +287,7 @@ install-others := $(addprefix $(inst_i18ndir)/, \
 			      $(locales))
 endif
 
-tests: $(objdir)/iconvdata/gconv-modules
+tests: $(gen-gconv-modules)
 
 tests-static += \
   tst-langinfo-newlocale-static \
@@ -412,6 +412,7 @@ LOCALES := \
   # LOCALES
 
 include ../gen-locales.mk
+include ../gen-gconv-modules.mk
 
 $(objpfx)tst-iconv-emojis-trans.out: $(gen-locales)
 
@@ -587,6 +588,3 @@ $(objpfx)mtrace-tst-leaks.out: $(objpfx)tst-leaks.out
 
 bug-setlocale1-ENV-only = LOCPATH=$(objpfx) LC_CTYPE=de_DE.UTF-8
 bug-setlocale1-static-ENV-only = $(bug-setlocale1-ENV-only)
-
-$(objdir)/iconvdata/gconv-modules:
-	$(MAKE) -C ../iconvdata subdir=iconvdata $@

wcsmbs/Makefile

@@ -213,10 +213,6 @@ xtests += test-wcsncmp-nonarray
 tests-internal += \
   tst-wcsmbs-clone-overflow
 
-tests-static += \
-  tst-wcsmbs-clone-overflow
-
-
 include ../Rules
 
 ifeq ($(run-built-tests),yes)
@@ -233,6 +229,7 @@ LOCALES := \
   zh_TW.EUC-TW \
   # LOCALES
 include ../gen-locales.mk
+include ../gen-gconv-modules.mk
 
 $(objpfx)tst-btowc.out: $(gen-locales)
 $(objpfx)tst-c16c32-1.out: $(gen-locales)
@@ -247,7 +244,7 @@ $(objpfx)tst-c32-state.out: $(gen-locales)
 $(objpfx)test-c8rtomb.out: $(gen-locales)
 $(objpfx)test-mbrtoc8.out: $(gen-locales)
 $(objpfx)tst-wscanf-to_inpunct.out: $(gen-locales)
-$(objpfx)tst-wcsmbs-clone-overflow.out: $(gen-locales)
+$(objpfx)tst-wcsmbs-clone-overflow.out: $(gen-locales) $(gen-gconv-modules)
 endif
 
 $(objpfx)tst-wcstod-round: $(libm)

wcsmbs/tst-wcsmbs-clone-overflow.c

@@ -30,8 +30,11 @@
 static int
 do_test (void)
 {
-  if (setlocale (LC_ALL, "de_DE.ISO-8859-1") == NULL)
-    FAIL_EXIT1 ("setlocale failed, check if de_DE.ISO-8859-1 is generated");
+  locale_t loc_obj = newlocale (LC_ALL_MASK, "de_DE.ISO-8859-1", NULL);
+  if (loc_obj == NULL)
+    FAIL_EXIT1 ("newlocale failed, check if de_DE.ISO-8859-1 is generated");
+
+  uselocale (loc_obj);
 
   wchar_t buf[32] = L"123";
   int j;
@@ -41,7 +44,7 @@ do_test (void)
     FAIL_EXIT1 ("swscanf failed");
 
   /* Retrieve the current gconv_fcts from the LC_CTYPE locale data.  */
-  struct __locale_data *loc = _NL_CURRENT_DATA (LC_CTYPE);
+  struct __locale_data *loc = loc_obj->__locales[LC_CTYPE];
   struct lc_ctype_data *ctype = loc->private;
   const struct gconv_fcts *fcts = ctype->fcts;
 
@@ -51,6 +54,9 @@ do_test (void)
   /* Capture the reference counter.  */
   int initial_counter = fcts->towc->__counter;
 
+  if (fcts->towc->__shlib_handle == NULL)
+    FAIL_EXIT1 ("__shlib_handle is NULL!");
+
   /* Perform a second iteration of swscanf. If the stack-allocated FILE
      leaks the gconv reference, the counter will increment.  */
   if (swscanf (buf, L"%d", &j) < 1)