[PATCH v7.1] gdb: set filename-display shortpath support

[Azat Khuzhin <a3at dot mail at gmail dot com>]

Display only non-common part of filename and compilation directory

This will be useful for projects that use separate build directory
inside project (like build/cmake and others).

gdb/
	* source.h (symtab_to_shortpath): Add it.
	* source.c (filename_display): Add shortpath display.
	(symtab_to_filename_for_display): Use symtab_to_shortpath.
	* NEWS (set filename-display shortpath): New entry.

gdb/doc/
	* gdb.texinfo (Backtrace): Added description of
	'filename-display shortpath' in 'set/show backtrace' section.
---
V2: fixed coding style issues (thanks to Joel)
V3: fixed typo in initial condition for symtab_to_shortpath
V4: add changelog into message (lost because of --annotate)
V5: use helpers from filenames.h instead of strncmp and SLASH_STRING.
(Thanks to Eli, who pointed me out to this.)
V6: conding style fixed in changelog and header file (thanks to Tom)
V7: add NEWS and doc.

 gdb/NEWS            |  5 +++++
 gdb/doc/gdb.texinfo |  3 +++
 gdb/source.c        | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++---
 gdb/source.h        |  3 +++
 4 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/gdb/NEWS b/gdb/NEWS
index ae84e00..76d8f29 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -3,6 +3,11 @@
 
 *** Changes since GDB 7.6
 
+* New options
+
+set filename-display shortpath
+  Display only non-common part of filenames and compilation directory.
+
 * GDB now supports Fission DWP file format version 2.
   http://gcc.gnu.org/wiki/DebugFission
 
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 87d5145..f26d473 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -6852,6 +6852,9 @@ Display an absolute filename.
 
 @item show filename-display
 Show the current way to display filenames.
+
+@item set filename-display shortpath
+Display only non-common part of filenames and compilation directory.
 @end table
 
 @node Frame Filter Management
diff --git a/gdb/source.c b/gdb/source.c
index 6234bfc..0ea3f88 100644
--- a/gdb/source.c
+++ b/gdb/source.c
@@ -111,11 +111,13 @@ show_lines_to_list (struct ui_file *file, int from_tty,
 static const char filename_display_basename[] = "basename";
 static const char filename_display_relative[] = "relative";
 static const char filename_display_absolute[] = "absolute";
+static const char filename_display_shortpath[] = "shortpath";
 
 static const char *const filename_display_kind_names[] = {
   filename_display_basename,
   filename_display_relative,
   filename_display_absolute,
+  filename_display_shortpath,
   NULL
 };
 
@@ -1137,6 +1139,48 @@ symtab_to_fullname (struct symtab *s)
 /* See commentary in source.h.  */
 
 const char *
+symtab_to_shortpath (struct symtab *symtab)
+{
+  const char *prev_slash_name = symtab->filename;
+  const char *prev_slash_dir = symtab->dirname;
+  const char *slash_name = symtab->filename;
+  const char *slash_dir = symtab->dirname;
+  const char *shortpath = slash_name;
+
+  if (slash_dir == NULL)
+    return shortpath;
+
+  for (; *slash_name && *slash_dir; slash_name++, slash_dir++)
+    {
+      size_t min_part_len;
+
+      if (IS_DIR_SEPARATOR (*slash_name) != IS_DIR_SEPARATOR (*slash_dir))
+        break;
+      if (!IS_DIR_SEPARATOR (*slash_name))
+        continue;
+
+      ++slash_name;
+      ++slash_dir;
+      if (!*slash_name || !*slash_dir)
+        break;
+
+      min_part_len = min (slash_name - prev_slash_name,
+                          slash_dir - prev_slash_dir);
+      if (filename_ncmp (slash_name, slash_dir, min_part_len))
+        break;
+
+      shortpath = slash_name;
+
+      prev_slash_name = slash_name;
+      prev_slash_dir = slash_dir;
+    }
+
+  return shortpath;
+}
+
+/* See commentary in source.h.  */
+
+const char *
 symtab_to_filename_for_display (struct symtab *symtab)
 {
   if (filename_display_string == filename_display_basename)
@@ -1145,6 +1189,8 @@ symtab_to_filename_for_display (struct symtab *symtab)
     return symtab_to_fullname (symtab);
   else if (filename_display_string == filename_display_relative)
     return symtab->filename;
+  else if (filename_display_string == filename_display_shortpath)
+    return symtab_to_shortpath (symtab);
   else
     internal_error (__FILE__, __LINE__, _("invalid filename_display_string"));
 }
@@ -2093,9 +2139,11 @@ is not specified, print all substitution rules."),
 Set how to display filenames."), _("\
 Show how to display filenames."), _("\
 filename-display can be:\n\
-  basename - display only basename of a filename\n\
-  relative - display a filename relative to the compilation directory\n\
-  absolute - display an absolute filename\n\
+  basename  - display only basename of a filename\n\
+  relative  - display a filename relative to the compilation directory\n\
+  absolute  - display an absolute filename\n\
+  shortpath - display only non-common part of filenames and compilation \
+directory\n\
 By default, relative filenames are displayed."),
 			NULL,
 			show_filename_display_string,
diff --git a/gdb/source.h b/gdb/source.h
index 33cad09..b94c88f 100644
--- a/gdb/source.h
+++ b/gdb/source.h
@@ -52,6 +52,9 @@ extern char *rewrite_source_path (const char *path);
 
 extern const char *symtab_to_fullname (struct symtab *s);
 
+/* Returns only non-common part of filename and compilation directory. */
+extern const char *symtab_to_shortpath (struct symtab *symtab);
+
 /* Returns filename without the compile directory part, basename or absolute
    filename.  It depends on 'set filename-display' value.  */
 extern const char *symtab_to_filename_for_display (struct symtab *symtab);
-- 
1.8.4.3