Re: [RFA] New substitute-path commands

[Joel Brobecker <brobecker@adacore.com>]

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Hello,

Here is a second take at this new functionality, updated as suggested:

> set substitute-path FROM TO
> 
>   [We can make it use buildargv for uniform quoting of TO and FROM. 
>   I'd recommend that.]
> 
> unset substitute-path FROM
> 
> show substitute-path

Added bonus, I included a documentation patch for review.

2006-07-06  Joel Brobecker  <brobecker@adacore.com

        * source.c (substitute_path_from): New static variable.
        (substitute_path_to): Likewise.
        (xrewrite_source_path): New function.
        (find_and_open_source): Add source path rewriting support.
        (show_substitute_path_command): New function.
        (unset_substitute_path_command): New function.
        (set_substitute_path_command): New function.
        (_initialize_source): Add new substitute-path commands.

Documentation ChangeLog entry:

        * gdb.texinfo (Source Path): Add documentation for new
        substitute-path commands.

Tested on x86-linux, no regression.

Thanks,
-- 
Joel

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Index: source.c
===================================================================
RCS file: /cvs/src/src/gdb/source.c,v
retrieving revision 1.75
diff -u -p -r1.75 source.c
--- source.c	15 May 2006 15:50:13 -0000	1.75
+++ source.c	7 Jul 2006 04:50:31 -0000
@@ -73,6 +73,11 @@ static void show_directories (char *, in
 
 char *source_path;
 
+/* Support for source path substitution commands.  */
+
+static char *substitute_path_from = NULL;
+static char *substitute_path_to = NULL;
+
 /* Symtab of default file for listing lines of.  */
 
 static struct symtab *current_source_symtab;
@@ -828,6 +833,47 @@ source_full_path_of (char *filename, cha
   return 1;
 }
 
+/* If the user specified a source path substitution rule, then
+   try applying it on PATH, and return the new path.  This new
+   path must be deallocated afterwards.
+   
+   Return NULL if no substitution rule was specified by the user,
+   or of this rule didn't apply to the given PATH.  */
+   
+static char *
+xrewrite_source_path (const char *path)
+{
+  char *from_start;
+  char *new_path;
+
+  /* If no path substitution rule was specified, then no rewrite
+     is actually needed.  */
+
+  if (substitute_path_from == NULL)
+    return NULL;
+
+  /* Search for the first occurence of SUBSTITUTE_PATH_FROM.
+     No substitution needed of not found.  */
+
+  from_start = strstr (path, substitute_path_from);
+
+  if (from_start == NULL)
+    return NULL;
+
+  /* Compute the rewritten path and return it.  */
+
+  new_path = (char *) xmalloc (strlen (path) + 1
+                               + strlen (substitute_path_to)
+                               - strlen (substitute_path_from));
+  strncpy (new_path, path, from_start - path);
+  strcpy (new_path + (from_start - path),
+          substitute_path_to);
+  strcat (new_path,
+          from_start + strlen (substitute_path_from));
+
+  return new_path;
+}
+
 /* This function is capable of finding the absolute path to a
    source file, and opening it, provided you give it an 
    OBJFILE and FILENAME. Both the DIRNAME and FULLNAME are only
@@ -844,7 +890,7 @@ source_full_path_of (char *filename, cha
      FULLNAME is set to the absolute path to the file just opened.
 
    On Failure
-     A non valid file descriptor is returned. ( the return value is negitive ) 
+     A non valid file descriptor is returned. ( the return value is negative ) 
      FULLNAME is set to NULL.  */
 int
 find_and_open_source (struct objfile *objfile,
@@ -857,8 +903,22 @@ find_and_open_source (struct objfile *ob
   int result;
 
   /* Quick way out if we already know its full name */
+
   if (*fullname)
     {
+      {
+        /* The user may have requested that source paths be rewritten
+           according to a substitution rule he provided.  Check if
+           this is the case, and do the rewrite if appropriate.  */
+        char *rewritten_fullname = xrewrite_source_path (*fullname);
+
+        if (rewritten_fullname != NULL)
+           {
+             xfree (*fullname);
+             *fullname = rewritten_fullname;
+           }
+      }
+
       result = open (*fullname, OPEN_MODE);
       if (result >= 0)
 	return result;
@@ -869,6 +929,27 @@ find_and_open_source (struct objfile *ob
 
   if (dirname != NULL)
     {
+      /* If necessary, rewrite the compilation directory name according
+         to the source path substitution rules specified by the user.
+
+         Normally, we should really try to do the rewrite on the entire
+         path as opposed to just the directory name, but that's making
+         things much more complicated since we now have to concat the
+         dirname and filename, apply the substitution rule, and then do
+         [...] ???  How do we split the path back into dirname and filename?
+         In practice, the source path substitution feature should be used
+         when the entire tree has been moved, in which case only the root
+         part of the tree path will need to be rewritten.  So this should
+         not be a problem in practice.  */
+
+      char *rewritten_dirname = xrewrite_source_path (dirname);
+
+      if (rewritten_dirname != NULL)
+        {
+          make_cleanup (xfree, rewritten_dirname);
+          dirname = rewritten_dirname;
+        }
+      
       /* Replace a path entry of  $cdir  with the compilation directory name */
 #define	cdir_len	5
       /* We cast strstr's result in case an ANSIhole has made it const,
@@ -1587,6 +1668,65 @@ reverse_search_command (char *regex, int
   fclose (stream);
   return;
 }
+
+/* Print the current source path substitution rule.  */
+
+static void
+show_substitute_path_command (char *args, int from_tty)
+{
+  if (substitute_path_from == NULL)
+    printf_filtered (_("No source path substitution rule specified.\n"));
+  else
+    printf_filtered (_("`%s' in source paths now substituted with `%s'.\n"),
+                     substitute_path_from, substitute_path_to);
+}
+
+/* Delete the current source path substitution rule.  */
+
+static void
+unset_substitute_path_command (char *args, int from_tty)
+{
+  if (substitute_path_from != NULL)
+    {
+      xfree (substitute_path_from);
+      substitute_path_from = NULL;
+    }
+
+  if (substitute_path_to != NULL)
+    {
+      xfree (substitute_path_to);
+      substitute_path_to = NULL;
+    }
+}
+
+/* Add a new source path substitution rule.  */
+
+static void
+set_substitute_path_command (char *args, int from_tty)
+{
+  char *from_path, *to_path;
+  char **argv = buildargv (args);
+
+  if (argv == NULL || argv[0] == NULL || argv [1] == NULL)
+    error (_("Incorrect usage, too few arguments in command"));
+
+  if (argv[2] != NULL)
+    error (_("Incorrect usage, too many arguments in command"));
+
+  /* Remove any previous substitution rule.  */
+
+  unset_substitute_path_command (NULL, from_tty);
+
+  /* Insert the new substitution rule, and print a confirmation message
+     to the user.  */
+
+  substitute_path_from = xstrdup (argv[0]);
+  substitute_path_to = xstrdup (argv[1]);
+  freeargv (argv);
+
+  show_substitute_path_command (NULL, from_tty);
+}
+
 \f
 void
 _initialize_source (void)
@@ -1666,4 +1806,19 @@ Show number of source lines gdb will lis
 			    NULL,
 			    show_lines_to_list,
 			    &setlist, &showlist);
+
+  add_cmd ("substitute-path", class_files, set_substitute_path_command,
+           _("\
+Add a source path substitution rule. If a substitution rule was previously\n\
+set, it is overridden."), &setlist);
+
+  add_cmd ("substitute-path", class_files, unset_substitute_path_command,
+           _("\
+Remove the current source path substitution rule.  Has no effect\n\
+if no path substitution rule was previously specified."),
+           &unsetlist);
+
+  add_cmd ("substitute-path", class_files, show_substitute_path_command,
+           _("Show the current source path substitution rule."),
+           &showlist);
 }

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Index: doc/gdb.texinfo
===================================================================
RCS file: /cvs/src/src/gdb/doc/gdb.texinfo,v
retrieving revision 1.340
diff -u -p -r1.340 gdb.texinfo
--- doc/gdb.texinfo	21 Jun 2006 13:57:21 -0000	1.340
+++ doc/gdb.texinfo	7 Jul 2006 04:51:00 -0000
@@ -5033,6 +5033,23 @@ To add other directories, use the @code{
 The search path is used to find both program source files and @value{GDBN}
 script files (read using the @samp{-command} option and @samp{source} command).
 
+In addition to the source path, @value{GDBN} provides a set of commands
+that manage a source path substitution rule.  Instead of attempting to
+locate the source file using the original source path as described above,
+it will first apply the substitution rule to that source path, and use
+the resulting path instead.  By default, there is no substitution rule
+defined, but this can be very useful in the case when your source tree
+has been moved to a different location from the one where the sources
+were compiled. To define a source path substitution rule, use the
+@code{set substitute-path} command.
+
+Using the previous example, suppose the @file{foo-1.0} tree has been
+moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
+GDB to replace @file{/usr/src} in all source path names with
+@file{/mnt/cross}.  The first lookup will then be
+@file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
+of @file{/usr/src/foo-1.0/lib/foo.c}.
+
 @table @code
 @item directory @var{dirname} @dots{}
 @item dir @var{dirname} @dots{}
@@ -5068,6 +5085,21 @@ Reset the source path to its default val
 @item show directories
 @kindex show directories
 Print the source path: show which directories it contains.
+
+@item set substitute-path @var{FROM} @var{TO}
+@kindex set substitute-path
+Define a source path substitution rule.  The new substitution rule
+replaces any rule previously defined.
+
+@item unset substitute-path
+@kindex unset substitute-path
+If a source path substitution rule is active, then cancel it.
+This command has no effect otherwise.
+
+@item show substitute-path
+@kindex show substitute-path
+Print the source path substitution rule if defined.
+
 @end table
 
 If your source path is cluttered with directories that are no longer of