[gimp/wip/bug792787-debug-stacktrace-GUI] app, tools: add support for ExcHndl/DrMinGW for Win32 debugging.

[Jehan Pagès <jehanp src gnome org>]

commit 3129d69f845c89764768f1cc330195d01ef23cdc
Author: Jehan <jehan girinstud io>
Date:   Fri Jan 26 21:20:52 2018 +0100

    app, tools: add support for ExcHndl/DrMinGW for Win32 debugging.
    
    The feature already exists in our code and produces backtraces upon a
    crash into a file. The only difference is that we are now getting the
    file contents and showing it in our new debug dialog, so that it works
    similarly on all platform (and therefore making the debug info visible
    to people, otherwise they would never report, even though the data is
    generated).
    The difference with gdb/lldb is that it doesn't allow backtraces at
    random points (for debugging non-fatal yet bad errors). Also the API has
    just 2 functions and in particular an ExcHndlInit() but no way to unload
    the feature. So we don't need the debugging page in Preferences because
    the switch option would not work. On Windows, the feature will be
    decided at build time only.
    
    Last point: the code is untested on Windows so far. I assume it would
    work, but there is at least one point I am unsure of: will ExcHndl have
    already generated the backtrace file when gimpdebug runs? If not, I will
    have to let gimp die first to be able to get the backtrace.

 app/app.c                        |    6 ++++--
 app/app.h                        |    3 ++-
 app/dialogs/preferences-dialog.c |    5 +++++
 app/errors.c                     |   13 ++++++++++---
 app/errors.h                     |    3 ++-
 app/main.c                       |   14 ++++++++------
 tools/Makefile.am                |    6 ++++++
 tools/gimpdebug.c                |   19 +++++++++++++++----
 8 files changed, 52 insertions(+), 17 deletions(-)
---
diff --git a/app/app.c b/app/app.c
index 345326f..593863a 100644
--- a/app/app.c
+++ b/app/app.c
@@ -173,7 +173,8 @@ app_run (const gchar         *full_prog_name,
          gboolean             use_debug_handler,
          gboolean             show_playground,
          GimpStackTraceMode   stack_trace_mode,
-         GimpPDBCompatMode    pdb_compat_mode)
+         GimpPDBCompatMode    pdb_compat_mode,
+         const gchar         *backtrace_file)
 {
   GimpInitStatusFunc  update_status_func = NULL;
   Gimp               *gimp;
@@ -247,7 +248,8 @@ app_run (const gchar         *full_prog_name,
 
   gimp_cpu_accel_set_use (use_cpu_accel);
 
-  errors_init (gimp, full_prog_name, use_debug_handler, stack_trace_mode);
+  errors_init (gimp, full_prog_name, use_debug_handler,
+               stack_trace_mode, backtrace_file);
 
   /*  Check if the user's gimp_directory exists
    */
diff --git a/app/app.h b/app/app.h
index 9f96216..47d9ebf 100644
--- a/app/app.h
+++ b/app/app.h
@@ -49,7 +49,8 @@ void  app_run       (const gchar         *full_prog_name,
                      gboolean             use_debug_handler,
                      gboolean             show_playground,
                      GimpStackTraceMode   stack_trace_mode,
-                     GimpPDBCompatMode    pdb_compat_mode);
+                     GimpPDBCompatMode    pdb_compat_mode,
+                     const gchar         *backtrace_file);
 
 
 #endif /* __APP_H__ */
diff --git a/app/dialogs/preferences-dialog.c b/app/dialogs/preferences-dialog.c
index 078c6d7..6c4a6a3 100644
--- a/app/dialogs/preferences-dialog.c
+++ b/app/dialogs/preferences-dialog.c
@@ -1229,6 +1229,11 @@ prefs_dialog_new (Gimp       *gimp,
   /***************/
   /*  Debugging  */
   /***************/
+  /* No debugging preferences are needed on win32. Either GIMP has been
+   * built with DrMinGW support (HAVE_EXCHNDL) or not. If it has, then
+   * the backtracing is enabled and can't be disabled. It assume it will
+   * work only upon a crash.
+   */
 #ifndef G_OS_WIN32
   vbox = gimp_prefs_box_add_page (GIMP_PREFS_BOX (prefs_box),
                                   /* TODO: icon needed. */
diff --git a/app/errors.c b/app/errors.c
index 4dea4e6..1e2a12c 100644
--- a/app/errors.c
+++ b/app/errors.c
@@ -52,6 +52,7 @@ static Gimp                *the_errors_gimp   = NULL;
 static gboolean             use_debug_handler = FALSE;
 static GimpStackTraceMode   stack_trace_mode  = GIMP_STACK_TRACE_QUERY;
 static gchar               *full_prog_name    = NULL;
+static gchar               *backtrace_file    = NULL;
 
 
 /*  local function prototypes  */
@@ -82,7 +83,8 @@ void
 errors_init (Gimp               *gimp,
              const gchar        *_full_prog_name,
              gboolean            _use_debug_handler,
-             GimpStackTraceMode  _stack_trace_mode)
+             GimpStackTraceMode  _stack_trace_mode,
+             const gchar        *_backtrace_file)
 {
   const gchar * const log_domains[] =
   {
@@ -131,6 +133,7 @@ errors_init (Gimp               *gimp,
   use_debug_handler = _use_debug_handler ? TRUE : FALSE;
   stack_trace_mode  = _stack_trace_mode;
   full_prog_name    = g_strdup (_full_prog_name);
+  backtrace_file    = g_strdup (_backtrace_file);
 
   for (i = 0; i < G_N_ELEMENTS (log_domains); i++)
     g_log_set_handler (log_domains[i],
@@ -149,6 +152,9 @@ void
 errors_exit (void)
 {
   the_errors_gimp = NULL;
+
+  if (backtrace_file)
+    g_free (backtrace_file);
 }
 
 void
@@ -283,8 +289,9 @@ gimp_eek (const gchar *reason,
           /* If enabled (it is disabled by default), the GUI preference
            * takes precedence over the command line argument.
            */
-          gchar *args[6] = { "gimpdebug-2.0", full_prog_name, NULL,
-                             (gchar *) reason, (gchar *) message, NULL };
+          gchar *args[7] = { "gimpdebug-2.0", full_prog_name, NULL,
+                             (gchar *) reason, (gchar *) message,
+                             backtrace_file, NULL };
           gchar  pid[16];
           gint   exit_status;
 
diff --git a/app/errors.h b/app/errors.h
index db73583..18c8e2c 100644
--- a/app/errors.h
+++ b/app/errors.h
@@ -26,7 +26,8 @@
 void   errors_init      (Gimp               *gimp,
                          const gchar        *full_prog_name,
                          gboolean            use_debug_handler,
-                         GimpStackTraceMode  stack_trace_mode);
+                         GimpStackTraceMode  stack_trace_mode,
+                         const gchar        *backtrace_file);
 void   errors_exit      (void);
 
 void   gimp_fatal_error (const gchar        *message) G_GNUC_NORETURN;
diff --git a/app/main.c b/app/main.c
index 603ff60..7b68167 100644
--- a/app/main.c
+++ b/app/main.c
@@ -305,6 +305,7 @@ main (int    argc,
   gchar          *basename;
   GFile          *system_gimprc_file = NULL;
   GFile          *user_gimprc_file   = NULL;
+  gchar          *backtrace_file     = NULL;
   gint            i;
 
 #if defined (__GNUC__) && defined (_WIN64)
@@ -369,7 +370,6 @@ main (int    argc,
     time_t t;
     gchar *filename;
     gchar *dir;
-    gchar *path;
 
     /* This has to be the non-roaming directory (i.e., the local
        directory) as backtraces correspond to the binaries on this
@@ -383,14 +383,12 @@ main (int    argc,
     time (&t);
     filename = g_strdup_printf ("%s-crash-%" G_GUINT64_FORMAT ".txt",
                                 g_get_prgname(), t);
-    path = g_build_filename (dir, filename, NULL);
+    backtrace_file = g_build_filename (dir, filename, NULL);
     g_free (filename);
     g_free (dir);
 
     ExcHndlInit ();
-    ExcHndlSetLogFileNameA (path);
-
-    g_free (path);
+    ExcHndlSetLogFileNameA (backtrace_file);
   }
 #endif
 
@@ -567,7 +565,11 @@ main (int    argc,
            use_debug_handler,
            show_playground,
            stack_trace_mode,
-           pdb_compat_mode);
+           pdb_compat_mode,
+           backtrace_file);
+
+  if (backtrace_file)
+    g_free (backtrace_file);
 
   if (system_gimprc_file)
     g_object_unref (system_gimprc_file);
diff --git a/tools/Makefile.am b/tools/Makefile.am
index 2be8413..795b57d 100644
--- a/tools/Makefile.am
+++ b/tools/Makefile.am
@@ -10,6 +10,12 @@ bin_PROGRAMS = \
        gimptool-2.0 \
        gimp-debug-resume
 
+if !ENABLE_GIMP_CONSOLE
+if HAVE_EXCHNDL
+bin_PROGRAMS += gimpdebug-2.0
+endif
+endif
+
 gimp_debug_resume_SOURCES = gimp-debug-resume.c
 
 else
diff --git a/tools/gimpdebug.c b/tools/gimpdebug.c
index 5ae723f..077acae 100644
--- a/tools/gimpdebug.c
+++ b/tools/gimpdebug.c
@@ -56,13 +56,15 @@ main (int    argc,
   const gchar *pid;
   const gchar *reason;
   const gchar *message;
-  gchar       *trace;
+  const gchar *bt_file = NULL;
+  gchar       *trace   = NULL;
   gchar       *error;
   GtkWidget   *dialog;
 
-  if (argc != 5)
+  if (argc != 5 && argc != 6)
     {
-      g_print ("Usage: gimpdebug-2.0 [PROGRAM] [PID] [REASON] [MESSAGE]\n");
+      g_print ("Usage: gimpdebug-2.0 [PROGRAM] [PID] [REASON] [MESSAGE] [BT_FILE]\n\n"
+               "Note: the backtrace file is optional and only used in Windows.\n");
       exit (EXIT_FAILURE);
     }
 
@@ -70,9 +72,18 @@ main (int    argc,
   pid     = argv[2];
   reason  = argv[3];
   message = argv[4];
+
   error   = g_strdup_printf ("%s: %s", reason, message);
 
-  trace   = gimp_debug_get_stack_trace (program, pid);
+  if (argc == 6)
+    {
+      bt_file = argv[5];
+      g_file_get_contents (bt_file, &trace, NULL, NULL);
+    }
+  else
+    {
+      trace = gimp_debug_get_stack_trace (program, pid);
+    }
 
   if (trace == NULL || strlen (trace) == 0)
     exit (EXIT_FAILURE);