Re: Debugging stack traces
Re: Debugging stack traces
- Subject: Re: Debugging stack traces
- From: Greg Parker <email@hidden>
- Date: Wed, 2 Dec 2009 17:21:44 -0800
On Dec 2, 2009, at 4:55 PM, Graham Cox wrote:
> When I get a stack trace in a crash report, as exampled below, can I use the offsets (+71, +50) to locate the relevant line in the source code? What do these numbers actually mean?
>
> 1 com.apptree.drawkit 0x001c7bb9 -[DKDrawableObject encodeWithCoder:] + 71
> 2 com.mapdiva.ortelius 0x0003c81d -[DKOSymbol encodeWithCoder:] + 50
That's the offset in bytes of the CPU instruction in that function - the crashing instruction in the top frame, and the instruction after the call in the other frames.
You can recover the line number if you have the binary and dSYM file that match the version from the crash.
(The values below are all fake.)
1. Find the binary's UUID in the Binary Images section of the crash log.
Binary Images:
0x1000 - 0x1ff7 +com.apptree.drawkit ??? (???) <A84E261F-B98E-8ECD-3A40-24C65353BE3E> /path/to/DrawKit.framework/Contents/MacOS/DrawKit
2. Find the binary for the version with that UUID.
% dwarfdump -u /path/to/DrawKit.framework
UUID: D0358F4B-FCBB-321A-5F9E-E4C36C20ADE9 (x86_64) /path/to/DrawKit.framework/Contents/MacOS/DrawKit
UUID: A84E261F-B98E-8ECD-3A40-24C65353BE3E (i386) /path/to/DrawKit.framework/Contents/MacOS/DrawKit
3. Find the dSYM file with that UUID. A Spotlight search for the UUID may work.
% dwarfdump -u /path/to/DrawKit.framework.dSYM
UUID: D0358F4B-FCBB-321A-5F9E-E4C36C20ADE9 (x86_64) /path/to/DrawKit.framework.dSYM/Contents/Resources/DWARF/DrawKit
UUID: A84E261F-B98E-8ECD-3A40-24C65353BE3E (i386) /path/to/DrawKit.framework.dSYM/Contents/Resources/DWARF/DrawKit
4. Run gdb with that architecture, binary, and dSYM.
% gdb -arch i386 /path/to/DrawKit.framework
(gdb) add-dsym /path/to/DrawKit.framework.dSYM
5. Ask gdb for the line number for that function+offset. (Note the actual address may not match the one in the crash log.)
(gdb) x/i '-[DKDrawableObject encodeWithCoder:]' + 71
0x4bb9 <-[DKDrawableObject encodeWithCoder:]+71> ...
(gdb) info line *0x4bb9
Line 55 of "DKDrawableObject.m" starts at address 0x4bb9 <-[DKDrawableObject encodeWithCoder:]+71> and ends at 0x4bc9 <-[DKDrawableObject encodeWithCoder:]+87>
--
Greg Parker email@hidden Runtime Wrangler
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