gdb: replace use of alloca with std::string in openp

This makes the code simpler and hopefully safer.

Change-Id: I30c7f0bc0c786621858d3f46d138f3b596dc49f5
Approved-By: Tom Tromey <tom@tromey.com>

diff --git a/gdb/source.c b/gdb/source.c
index b35d0a5f423cef1661a22303a3722cface24cd1c..c2f21279dadae79c4c0d015858027f2f3bab627c 100644 (file)
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -777,8 +777,7 @@ openp (const char *path, openp_flags opts, const char *string,
        const char *cwd)
 {
   int fd;
-  char *filename;
-  int alloclen;
+  std::string filename;
   /* The errno set for the last name we tried to open (and
      failed).  */
   int last_errno = 0;
@@ -812,16 +811,14 @@ openp (const char *path, openp_flags opts, const char *string,
 
       if (is_regular_file (string, &reg_file_errno))
        {
-         filename = (char *) alloca (strlen (string) + 1);
-         strcpy (filename, string);
-         fd = gdb_open_cloexec (filename, mode, 0).release ();
+         filename = string;
+         fd = gdb_open_cloexec (filename.c_str (), mode, 0).release ();
          if (fd >= 0)
            goto done;
          last_errno = errno;
        }
       else
        {
-         filename = NULL;
          fd = -1;
          last_errno = reg_file_errno;
        }
@@ -835,9 +832,6 @@ openp (const char *path, openp_flags opts, const char *string,
   /* Remove characters from the start of PATH that we don't need when PATH
      is appended to a directory name.  */
   string = prepare_path_for_appending (string);
-
-  alloclen = strlen (path) + strlen (string) + 2;
-  filename = (char *) alloca (alloclen);
   fd = -1;
   last_errno = ENOENT;
 
@@ -846,46 +840,20 @@ openp (const char *path, openp_flags opts, const char *string,
   for (const gdb::unique_xmalloc_ptr<char> &dir_up : dir_vec)
     {
       char *dir = dir_up.get ();
-      size_t len = strlen (dir);
       int reg_file_errno;
 
       if (strcmp (dir, "$cwd") == 0)
        {
          /* Name is $cwd -- insert current directory name instead.  */
-         int newlen;
-
-         /* First, realloc the filename buffer if too short.  */
-         len = strlen (cwd);
-         newlen = len + strlen (string) + 2;
-         if (newlen > alloclen)
-           {
-             alloclen = newlen;
-             filename = (char *) alloca (alloclen);
-           }
-         strcpy (filename, cwd);
+         filename = cwd;
        }
-      else if (strchr(dir, '~'))
+      else if (strchr (dir, '~'))
        {
-        /* See whether we need to expand the tilde.  */
-         int newlen;
-
-         gdb::unique_xmalloc_ptr<char> tilde_expanded (tilde_expand (dir));
-
-         /* First, realloc the filename buffer if too short.  */
-         len = strlen (tilde_expanded.get ());
-         newlen = len + strlen (string) + 2;
-         if (newlen > alloclen)
-           {
-             alloclen = newlen;
-             filename = (char *) alloca (alloclen);
-           }
-         strcpy (filename, tilde_expanded.get ());
+         /* See whether we need to expand the tilde.  */
+         filename = gdb::unique_xmalloc_ptr<char> (tilde_expand (dir)).get ();
        }
       else
        {
-         /* Normal file name in path -- just use it.  */
-         strcpy (filename, dir);
-
          /* Don't search $cdir.  It's also a magic path like $cwd, but we
             don't have enough information to expand it.  The user *could*
             have an actual directory named '$cdir' but handling that would
@@ -895,16 +863,19 @@ openp (const char *path, openp_flags opts, const char *string,
             $cdir must have already been expanded to the correct value.  */
          if (strcmp (dir, "$cdir") == 0)
            continue;
+
+         /* Normal file name in path -- just use it.  */
+         filename = dir;
        }
 
       /* Remove trailing slashes.  */
-      while (len > 0 && IS_DIR_SEPARATOR (filename[len - 1]))
-       filename[--len] = 0;
+      while (!filename.empty () && IS_DIR_SEPARATOR (filename.back ()))
+       filename.pop_back ();
 
-      strcat (filename + len, SLASH_STRING);
-      strcat (filename, string);
+      filename += SLASH_STRING;
+      filename += string;
 
-      if (is_regular_file (filename, &reg_file_errno))
+      if (is_regular_file (filename.c_str (), &reg_file_errno))
        {
          fd = gdb_open_cloexec (filename, mode, 0).release ();
          if (fd >= 0)
@@ -922,10 +893,10 @@ done:
       if (fd < 0)
        filename_opened->reset (NULL);
       else if ((opts & OPF_RETURN_REALPATH) != 0)
-       *filename_opened = gdb_realpath (filename);
+       *filename_opened = gdb_realpath (filename.c_str ());
       else
        *filename_opened
-         = make_unique_xstrdup (gdb_abspath (filename, cwd).c_str ());
+         = make_unique_xstrdup (gdb_abspath (filename.c_str (), cwd).c_str ());
     }
 
   errno = last_errno;