RunModalForDirector crashes with Program received signal: "EXC_BAD_ACCESS"

Question

I am new to objective-c programming and I am trying to fix a bug in some existing code. So apologies if the solution to my problem is simple.
The following section of code crashes with a Program received signal: “EXCBADACCESS” error message when trying to open a window and I don't know why.
[oPanel runModalForDirectory:nil file:nil types:fileTypes]
in the following function:
NSString * SelectDirectory()
NSString* fname;
fname = nil;
// printf("loading files\n");
NSArray *fileTypes = [NSArray arrayWithObjects:@"asc", nil];
// Create the File Open Panel class.
NSOpenPanel* oPanel = [NSOpenPanel openPanel];
[oPanel setCanChooseDirectories:YES];
[oPanel setCanChooseFiles:NO];
[oPanel setCanCreateDirectories:YES];
[oPanel setAllowsMultipleSelection:NO];
[oPanel setAlphaValue:0.95];
[oPanel setTitle:@"Select a directory to open"];
// Display the dialog. If the OK button was pressed, process the files.
if ( [oPanel runModalForDirectory:nil file:nil types:fileTypes] == NSOKButton )
NSLog(@"fname before assignment: %@",fname);
// Get an array containing the full filenames of all files and directories selected.
fname = [oPanel filename];
NSLog(@"fname after assignment: %@",fname);
else
fname = nil;
// printf("No directory Selected");
return (fname);
And the output from backtrace is:
gdb) backtrace
#0 0x005f7733 in gleRunVertexSubmitImmediate ()
#1 0x005f554a in gleLLVMArrayFunc ()
#2 0x005f554a in gleLLVMArrayFunc ()
#3 0x005f54d7 in gleSetVertexArrayFunc ()
#4 0x005d079a in gleDrawArraysOrElements_ExecCore ()
#5 0x005d2c8d in gleDrawArraysOrElementsVBOExec ()
#6 0x95609aa4 in glDrawElements ()
#7 0x00019521 in -[MyFooGLView drawRect:] (self=0x1ab740, _cmd=0x962df5d0, rect={origin = {x = 406, y = 0}, size = {width = 275, height = 5}}) at /Users/kinglab/Desktop/C3.3.5/MyFooGLView.m:2443
#8 0x97779bf8 in -[NSView _drawRect:clip:] ()
#9 0x97777469 in -[NSView _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectFor View:topView:] ()
#10 0x97777e9f in -[NSView _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectFor View:topView:] ()
#11 0x97777e9f in -[NSView _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectFor View:topView:] ()
#12 0x97776987 in -[NSThemeFrame _recursiveDisplayRectIfNeededIgnoringOpacity:isVisibleRect:rectIsVisibleRectFor View:topView:] ()
#13 0x977734ab in -[NSView _displayRectIgnoringOpacity:isVisibleRect:rectIsVisibleRectForView:] ()
#14 0x976b3e7b in -[NSView displayIfNeeded] ()
#15 0x976b3a29 in -[NSWindow displayIfNeeded] ()
#16 0x976b384c in _handleWindowNeedsDisplay ()
#17 0x95c31772 in __CFRunLoopDoObservers ()
#18 0x95c32acc in CFRunLoopRunSpecific ()
#19 0x95c33aa8 in CFRunLoopRunInMode ()
#20 0x96f2a2ac in RunCurrentEventLoopInMode ()
#21 0x96f29ffe in ReceiveNextEventCommon ()
#22 0x96f29f39 in BlockUntilNextEventMatchingListInMode ()
#23 0x976b16d5 in _DPSNextEvent ()
#24 0x976b0f88 in -[NSApplication nextEventMatchingMask:untilDate:inMode:dequeue:] ()
#25 0x978ee38d in -[NSApplication _realDoModalLoop:peek:] ()
#26 0x978e8acb in -[NSApplication runModalForWindow:] ()
#27 0x978d9bb6 in -[NSSavePanel(NSSavePanelRuntime) runModalForDirectory:file:types:] ()
#28 0x00004794 in SelectDirectory () at /Users/kinglab/Desktop/C3.3.5/FracController.m:42
#29 0x0000ecb5 in -[MyFooGLView LoadSurfBut:] (self=0x1ab740, _cmd=0x2db85, sender=0x12a130) at /Users/kinglab/Desktop/C3.3.5/MyFooGLView.m:633
#30 0x97782e8f in -[NSApplication sendAction:to:from:] ()
#31 0x97782dcc in -[NSControl sendAction:to:] ()
#32 0x97782c52 in -[NSCell _sendActionFrom:] ()
#33 0x977822ab in -[NSCell trackMouse:inRect:ofView:untilMouseUp:] ()
#34 0x97781afe in -[NSButtonCell trackMouse:inRect:ofView:untilMouseUp:] ()
#35 0x977813b8 in -[NSControl mouseDown:] ()
#36 0x9777faf7 in -[NSWindow sendEvent:] ()
#37 0x9774c6a5 in -[NSApplication sendEvent:] ()
#38 0x976a9fe7 in -[NSApplication run] ()
#39 0x976771d8 in NSApplicationMain ()
#40 0x0000202c in main (argc=1, argv=0xbfffe7cc) at /Users/kinglab/Desktop/C3.3.5/main.m:15

Answer 1

The problem doesn't seem to be with SelectDirectory(), it is with MyFooGLView. Perhaps that view is trying to do something that requires the event loop but you have it locked up in your modal dialog. Try using callbacks in a modeless dialog instead.