support: Add xstrndup, xunlink, xreadlink, support_create_temp_directory

10 files changed, 207 insertions, 5 deletions

diff --git a/support/Makefile b/support/Makefile
index 027a663..dafb173 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -109,19 +109,22 @@ libsupport-routines = \
   xpthread_once \
   xpthread_rwlock_init \
   xpthread_rwlock_rdlock \
-  xpthread_rwlock_wrlock \
   xpthread_rwlock_unlock \
+  xpthread_rwlock_wrlock \
   xpthread_rwlockattr_init \
   xpthread_rwlockattr_setkind_np \
   xpthread_sigmask \
   xpthread_spin_lock \
   xpthread_spin_unlock \
+  xreadlink \
   xrealloc \
   xrecvfrom \
   xsendto \
   xsetsockopt \
   xsocket \
   xstrdup \
+  xstrndup \
+  xunlink \
   xwaitpid \
   xwrite \
 
@@ -138,6 +141,7 @@ tests = \
   tst-support_capture_subprocess \
   tst-support_format_dns_packet \
   tst-support_record_failure \
+  tst-xreadlink \
 
 ifeq ($(run-built-tests),yes)
 tests-special = \
diff --git a/support/support.h b/support/support.h
index 4b5f04c..bbba803 100644
--- a/support/support.h
+++ b/support/support.h
@@ -68,6 +68,7 @@ void *xrealloc (void *p, size_t n);
 char *xasprintf (const char *format, ...)
   __attribute__ ((format (printf, 1, 2), malloc));
 char *xstrdup (const char *);
+char *xstrndup (const char *, size_t);
 
 __END_DECLS
 
diff --git a/support/support_chroot.c b/support/support_chroot.c
index f3ef551..f6fad18 100644
--- a/support/support_chroot.c
+++ b/support/support_chroot.c
@@ -46,10 +46,11 @@ support_chroot_create (struct support_chroot_configuration conf)
 {
   struct support_chroot *chroot = xmalloc (sizeof (*chroot));
 
-  chroot->path_chroot = xasprintf ("%s/tst-resolv-res_init-XXXXXX", test_dir);
-  if (mkdtemp (chroot->path_chroot) == NULL)
-    FAIL_EXIT1 ("mkdtemp (\"%s\"): %m", chroot->path_chroot);
-  add_temp_file (chroot->path_chroot);
+  {
+    char *template = xasprintf ("%s/tst-resolv-res_init-XXXXXX", test_dir);
+    chroot->path_chroot = support_create_temp_directory (template);
+    free (template);
+  }
 
   /* Create the /etc directory in the chroot environment.  */
   char *path_etc = xasprintf ("%s/etc", chroot->path_chroot);
diff --git a/support/temp_file.c b/support/temp_file.c
index fdb2477..cbd54e2 100644
--- a/support/temp_file.c
+++ b/support/temp_file.c
@@ -86,6 +86,19 @@ create_temp_file (const char *base, char **filename)
   return fd;
 }
 
+char *
+support_create_temp_directory (const char *base)
+{
+  char *base_copy = xstrdup (base);
+  if (mkdtemp (base_copy) == NULL)
+    {
+      printf ("error: mkdtemp (\"%s\"): %m", base);
+      exit (1);
+    }
+  add_temp_file (base_copy);
+  return base_copy;
+}
+
 /* Helper functions called by the test skeleton follow.  */
 
 void
diff --git a/support/temp_file.h b/support/temp_file.h
index 6fed8df..dfefe58 100644
--- a/support/temp_file.h
+++ b/support/temp_file.h
@@ -32,6 +32,11 @@ void add_temp_file (const char *name);
    *FILENAME.  */
 int create_temp_file (const char *base, char **filename);
 
+/* Create a temporary directory and schedule it for deletion.  BASE
+   must end with the six characters "XXXXXX".  Return the name of the
+   temporary directory.  The caller should free the string.  */
+char *support_create_temp_directory (const char *base);
+
 __END_DECLS
 
 #endif /* SUPPORT_TEMP_FILE_H */
diff --git a/support/tst-xreadlink.c b/support/tst-xreadlink.c
new file mode 100644
index 0000000..cb2c12a
--- /dev/null
+++ b/support/tst-xreadlink.c
@@ -0,0 +1,72 @@
+/* Test the xreadlink function.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+
+static int
+do_test (void)
+{
+  char *dir = support_create_temp_directory ("/tmp/tst-xreadlink-XXXXXX");
+  char *symlink_name = xasprintf ("%s/symlink", dir);
+  add_temp_file (symlink_name);
+
+  /* The limit 10000 is arbitrary and simply there to prevent an
+     attempt to exhaust all available disk space.  */
+  for (int size = 1; size < 10000; ++size)
+    {
+      char *contents = xmalloc (size + 1);
+      for (int i = 0; i < size; ++i)
+        contents[i] = 'a' + (rand () % 26);
+      contents[size] = '\0';
+      if (symlink (contents, symlink_name) != 0)
+        {
+          if (errno == ENAMETOOLONG)
+            {
+              printf ("info: ENAMETOOLONG failure at %d bytes\n", size);
+              free (contents);
+              break;
+            }
+          FAIL_EXIT1 ("symlink (%d bytes): %m", size);
+        }
+
+      char *readlink_result = xreadlink (symlink_name);
+      TEST_VERIFY (strcmp (readlink_result, contents) == 0);
+      free (readlink_result);
+      xunlink (symlink_name);
+      free (contents);
+    }
+
+  /* Create an empty file to suppress the temporary file deletion
+     warning.  */
+  xclose (xopen (symlink_name, O_WRONLY | O_CREAT, 0));
+
+  free (symlink_name);
+  free (dir);
+
+  return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/support/xreadlink.c b/support/xreadlink.c
new file mode 100644
index 0000000..aec58a2
--- /dev/null
+++ b/support/xreadlink.c
@@ -0,0 +1,44 @@
+/* Error-checking, allocating wrapper for readlink.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <scratch_buffer.h>
+#include <support/check.h>
+#include <support/support.h>
+#include <xunistd.h>
+
+char *
+xreadlink (const char *path)
+{
+  struct scratch_buffer buf;
+  scratch_buffer_init (&buf);
+
+  while (true)
+    {
+      ssize_t count = readlink (path, buf.data, buf.length);
+      if (count < 0)
+        FAIL_EXIT1 ("readlink (\"%s\"): %m", path);
+      if (count < buf.length)
+        {
+          char *result = xstrndup (buf.data, count);
+          scratch_buffer_free (&buf);
+          return result;
+        }
+      if (!scratch_buffer_grow (&buf))
+        FAIL_EXIT1 ("scratch_buffer_grow in xreadlink");
+    }
+}
diff --git a/support/xstrndup.c b/support/xstrndup.c
new file mode 100644
index 0000000..d59a283
--- /dev/null
+++ b/support/xstrndup.c
@@ -0,0 +1,30 @@
+/* strndup with error checking.
+   Copyright (C) 2016-2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/support.h>
+
+#include <string.h>
+
+char *
+xstrndup (const char *s, size_t length)
+{
+  char *p = strndup (s, length);
+  if (p == NULL)
+    oom_error ("strndup", length);
+  return p;
+}
diff --git a/support/xunistd.h b/support/xunistd.h
index c947bfd..05c2626 100644
--- a/support/xunistd.h
+++ b/support/xunistd.h
@@ -38,6 +38,11 @@ int xopen (const char *path, int flags, mode_t);
 void xstat (const char *path, struct stat64 *);
 void xmkdir (const char *path, mode_t);
 void xchroot (const char *path);
+void xunlink (const char *path);
+
+/* Read the link at PATH.  The caller should free the returned string
+   with free.  */
+char *xreadlink (const char *path);
 
 /* Close the file descriptor.  Ignore EINTR errors, but terminate the
    process on other errors.  */
diff --git a/support/xunlink.c b/support/xunlink.c
new file mode 100644
index 0000000..f94ee11
--- /dev/null
+++ b/support/xunlink.c
@@ -0,0 +1,27 @@
+/* Error-checking wrapper for unlink.
+   Copyright (C) 2017 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <support/check.h>
+#include <support/xunistd.h>
+
+void
+xunlink (const char *path)
+{
+  if (unlink (path) != 0)
+    FAIL_EXIT1 ("unlink (\"%s\"): %m", path);
+}