Don't hard code the number of stack frames after wxOnAssert().

The number of frames between the code containing the assert and the code
generating the stack trace is not the same under different platforms and so
hardcoding 8 for it in wxAppTraitsBase::GetAssertStackTrace() worked for wxMSW
but not e.g. wxGTK.

Instead, just ignore all frames up to and including the one for wxOnAssert()
itself. This makes the code work correctly on all platforms and it also won't
need to be modified whenever any extra functions are added/removed
(wxGTK-specific code in utilsgtk.cpp used wrong number of frames too, even
though it was presumably correct once before).

src/gtk/utilsgtk.cpp

@@ -20,6 +20,7 @@
 #include "wx/apptrait.h"
 #include "wx/process.h"
 #include "wx/sysopt.h"
+#include "wx/vector.h"
 
 #include "wx/gtk/private/timer.h"
 #include "wx/evtloop.h"
@@ -254,30 +255,68 @@ class StackDump : public wxStackWalker
 public:
     StackDump(GtkAssertDialog *dlg) { m_dlg=dlg; }
 
+    void ShowStackInDialog()
+    {
+        ProcessFrames(0);
+
+        for ( wxVector<Frame>::const_iterator it = m_frames.begin();
+              it != m_frames.end();
+              ++it )
+        {
+            gtk_assert_dialog_append_stack_frame(m_dlg,
+                                                 it->name.utf8_str(),
+                                                 it->file.utf8_str(),
+                                                 it->line);
+        }
+
+        m_frames.clear();
+    }
+
 protected:
     virtual void OnStackFrame(const wxStackFrame& frame) wxOVERRIDE
     {
-        wxString fncname = frame.GetName();
-
-        // append this stack frame's info in the dialog
-        if (!frame.GetFileName().empty() || !fncname.empty())
+        const wxString name = frame.GetName();
+        if ( name.StartsWith("wxOnAssert") )
         {
-            gtk_assert_dialog_append_stack_frame(m_dlg,
-                                                fncname.utf8_str(),
-                                                frame.GetFileName().utf8_str(),
-                                                frame.GetLine());
+            // Ignore all frames until the wxOnAssert() one, just as we do in
+            // wxAppTraitsBase::GetAssertStackTrace().
+            m_frames.clear();
+            return;
         }
+
+        // Also ignore frames which don't have neither the function name nor
+        // the file name, showing them in the dialog wouldn't provide any
+        // useful information.
+        if ( name.empty() && frame.GetFileName().empty() )
+            return;
+
+        m_frames.push_back(Frame(frame));
     }
 
 private:
     GtkAssertDialog *m_dlg;
+
+    struct Frame
+    {
+        explicit Frame(const wxStackFrame& f)
+            : name(f.GetName()),
+              file(f.GetFileName()),
+              line(f.GetLine())
+        {
+        }
+
+        wxString name;
+        wxString file;
+        int line;
+    };
+
+    wxVector<Frame> m_frames;
 };
 
 static void get_stackframe_callback(void* p)
 {
     StackDump* dump = static_cast<StackDump*>(p);
-    // skip over frames up to including wxOnAssert()
-    dump->ProcessFrames(6);
+    dump->ShowStackInDialog();
 }
 
 #endif // wxDEBUG_LEVEL && wxUSE_STACKWALKER