RFC: user auto-load directory

["Jim Blandy" <jimb at red-bean dot com>]

This patch adds a new parameter, 'maintenance set/show python
auto-load-user-directory', naming a directory that GDB searches for
Python scripts for loaded objfiles.  It just uses the basename of the
objfile.

I want to be able to define my own per-object pretty-printers, etc.,
but I don't want to have to copy or symlink .py files into object
directories that get blown away regularly, so the same-dir-as-object
rule doesn't work for me.  I don't want to mess with my
debug-file-directory settings.

Perhaps we should load the file we find in auto-load-user-directory
after also loading files we find by the existing rules?

If folks think the idea is good, I'll write docs.

gdb
        * python/python.c: #include "filenames.h" and "readline/readline.h".
        (gdbpy_auto_load_user_dir): New variable.
        (gdbpy_new_objfile): Check the auto-load user directory, too.
        (_initialize_python): Define 'maintenance set/show python
        auto-load-user-directory' command.  Add explanation of search
        process to help for 'maint set/show python auto-load'.

diff --git a/gdb/python/python.c b/gdb/python/python.c
index 9f1c8a4..c1793e8 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -39,6 +39,10 @@ static int gdbpy_should_print_stack = 1;
    opened, false otherwise.  */
 static int gdbpy_auto_load = 1;
 
+/* If not the empty string, this is the directory we should check
+   for the user's per-object Python code.  */
+static char *gdbpy_auto_load_user_dir;
+
 #ifdef HAVE_PYTHON
 
 #include "python.h"
@@ -58,6 +62,8 @@ static int gdbpy_auto_load = 1;
 #include "target.h"
 #include "gdbthread.h"
 #include "event-top.h"
+#include "filenames.h"
+#include "readline/readline.h"
 
 
 static PyMethodDef GdbMethods[];
@@ -740,6 +746,36 @@ gdbpy_new_objfile (struct objfile *objfile)
 
   input = fopen (filename, "r");
 
+  if (!input && gdbpy_auto_load_user_dir && gdbpy_auto_load_user_dir[0])
+    {
+      /* Check for a file in the user's auto-load directory.  */
+      char *user_dir = tilde_expand (gdbpy_auto_load_user_dir);
+      int user_dir_len = strlen (user_dir);
+      const char *basename, *p;
+      char *userfile;
+      
+      /* Find last component of object file's path.  */
+      basename = NULL;
+      for (p = filename; *p; p++)
+        if (IS_DIR_SEPARATOR (*p))
+          basename = p + 1;
+      if (! basename)
+        basename = filename;
+
+      /* Compute "AUTO-LOAD_USER_DIR/BASE-gdb.py".  Use the
+         GDBPY_AUTO_FILENAME appended above.  */
+      userfile = xmalloc (user_dir_len + 1 + (p - basename) + 1);
+      memcpy (userfile, user_dir, user_dir_len);
+      userfile[user_dir_len] = '/';
+      strcpy (userfile + user_dir_len + 1, basename);
+
+      xfree (user_dir);
+      xfree (filename);
+      filename = userfile;
+
+      input = fopen (filename, "r");
+    }
+
   if (!input && debug_file_directory)
     {
       /* Also try the same file in the separate debug info directory.  */
@@ -1433,11 +1469,32 @@ Enables or disables printing of Python stack traces."),
 			   &gdbpy_auto_load, _("\
 Enable or disable auto-loading of Python code when an object is opened."), _("\
 Show whether Python code will be auto-loaded when an object is opened."), _("\
-Enables or disables auto-loading of Python code when an object is opened."),
+When GDB reads debugging information for an executable or shared library,\n\
+it looks in various places for Python code to load associated with that\n\
+object file.  For an object file named OBJFILE in directory DIR, GDB\n\
+checks for a script under the following names:\n\
+  DIR/BASE-gdb.py\n\
+    (that is, in the same directory as the object file)\n\
+  PYTHON-AUTO-LOAD-USER-DIRECTORY/BASE-gdb.py\n\
+    (see 'help maintenance set python auto-load-user-directory')\n\
+  DEBUG-FILE-DIRECTORY/DIR/BASE-gdb.py\n\
+    (see 'help set debug-file-directory')\n\
+GDB loads the first one of these it finds."),
 			   NULL, NULL,
 			   &set_python_list,
 			   &show_python_list);
 
+  add_setshow_optional_filename_cmd ("auto-load-user-directory", class_maintenance,
+                                     &gdbpy_auto_load_user_dir, _("\
+Set directory holding user Python code to load when an object is opened."),
+                                     _("\
+Show directory holding user Python code to load when an object is opened."),
+                                     _("\
+See 'help maintenance set python auto-load' for details."),
+                                     NULL, NULL,
+                                     &set_python_list,
+                                     &show_python_list);
+
 #ifdef HAVE_PYTHON
   Py_Initialize ();
   PyEval_InitThreads ();