ctype: Fallback initialization of TLS using relocations (bug 19341, bug 32483)

This ensures that the ctype data pointers in TLS are valid
in secondary namespaces even without initialization via
__ctype_init.

Reviewed-by: Frédéric Bérat <fberat@redhat.com>

ctype/Makefile

@@ -36,6 +36,23 @@ aux := ctype-info
 
 tests := \
   test_ctype \
+  tst-ctype-tls-dlmopen \
+  tst-ctype-tls-dlopen-static \
   # tests
 
+tests-static := \
+  tst-ctype-tls-dlopen-static \
+  # tests-static
+
+modules-names := \
+  tst-ctype-tls-mod \
+  # modules-names
+
 include ../Rules
+
+$(objpfx)tst-ctype-tls-dlmopen: $(shared-thread-library)
+$(objpfx)tst-ctype-tls-dlmopen.out: $(objpfx)tst-ctype-tls-mod.so
+$(objpfx)tst-ctype-tls-dlopen-static: $(static-thread-library)
+$(objpfx)tst-ctype-tls-dlopen-static.out: $(objpfx)tst-ctype-tls-mod.so
+tst-ctype-tls-dlopen-static-ENV = \
+  LD_LIBRARY_PATH=$(ld-library-path):$(common-objpfx):$(common-objpfx)elf

ctype/ctype-info.c

@@ -19,9 +19,17 @@
 #include <ctype.h>
 #include <locale/localeinfo.h>
 
-__thread const uint16_t * __libc_tsd_CTYPE_B;
-__thread const int32_t * __libc_tsd_CTYPE_TOLOWER;
-__thread const int32_t * __libc_tsd_CTYPE_TOUPPER;
+/* Fallback initialization using relocations.  See the _nl_C_locobj
+   initializers in locale/xlocale.c.  Usually, this is overwritten by
+   __ctype_init before user code runs, but this does not happen for
+   threads in secondary namespaces.  With the initializers, secondary
+   namespaces at least get locale data from the C locale.  */
+__thread const uint16_t * __libc_tsd_CTYPE_B
+  = (const uint16_t *) _nl_C_LC_CTYPE_class + 128;
+__thread const int32_t * __libc_tsd_CTYPE_TOLOWER
+  = (const int32_t *) _nl_C_LC_CTYPE_tolower + 128;
+__thread const int32_t * __libc_tsd_CTYPE_TOUPPER
+  = (const int32_t *) _nl_C_LC_CTYPE_toupper + 128;
 
 
 void

ctype/tst-ctype-tls-dlmopen.c

@@ -0,0 +1,2 @@
+#define DO_STATIC_TEST 0
+#include "tst-ctype-tls-skeleton.c"

ctype/tst-ctype-tls-dlopen-static.c

@@ -0,0 +1,2 @@
+#define DO_STATIC_TEST 1
+#include "tst-ctype-tls-skeleton.c"

ctype/tst-ctype-tls-mod.c

@@ -0,0 +1,37 @@
+/* Wrappers for <ctype.h> macros in a secondary namespace.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <ctype.h>
+
+int
+my_isalpha (int ch)
+{
+  return isalpha (ch);
+}
+
+int
+my_toupper (int ch)
+{
+  return toupper (ch);
+}
+
+int
+my_tolower (int ch)
+{
+  return tolower (ch);
+}

ctype/tst-ctype-tls-skeleton.c

@@ -0,0 +1,67 @@
+/* Test that <ctype.h> in a secondary namespace works.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* Before this file is included, define DO_STATIC_TEST to 0 or 1.
+   With 0, dlmopen is used for the test.  With 1, dlopen is used.  */
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/xdlfcn.h>
+#include <support/xthread.h>
+
+static int (*my_isalpha) (int);
+static int (*my_toupper) (int);
+static int (*my_tolower) (int);
+
+static void *
+checks (void *ignore)
+{
+  TEST_VERIFY (my_isalpha ('a'));
+  TEST_VERIFY (!my_isalpha ('0'));
+  TEST_COMPARE (my_toupper ('a'), 'A');
+  TEST_COMPARE (my_toupper ('A'), 'A');
+  TEST_COMPARE (my_tolower ('a'), 'a');
+  TEST_COMPARE (my_tolower ('A'), 'a');
+  return NULL;
+}
+
+static int
+do_test (void)
+{
+  char *dso = xasprintf ("%s/ctype/tst-ctype-tls-mod.so", support_objdir_root);
+#if DO_STATIC_TEST
+  void *handle = xdlopen (dso, RTLD_LAZY);
+#else
+  void *handle = xdlmopen (LM_ID_NEWLM, dso, RTLD_LAZY);
+#endif
+  my_isalpha = xdlsym (handle, "my_isalpha");
+  my_toupper = xdlsym (handle, "my_toupper");
+  my_tolower = xdlsym (handle, "my_tolower");
+
+  checks (NULL);
+  xpthread_join (xpthread_create (NULL, checks, NULL));
+
+  xdlclose (handle);
+  free (dso);
+
+  return 0;
+}
+
+#include <support/test-driver.c>