Re: XCode debugger won't launch my app
Re: XCode debugger won't launch my app
- Subject: Re: XCode debugger won't launch my app
- From: Jim Ingham <email@hidden>
- Date: Thu, 6 May 2004 10:50:21 -0700
We have a bug which looks somewhat like this. The conditions of the
bug are:
1) you have a framework with a default load address of 0x0 - this is
the default when you don't specify anything with the -seg1addr linker
flag.
2) You are setting a breakpoint in the framework.
3) The breakpoint is at a low address in the framework
The bug is that gdb writes its breakpoints into the debugee program
right when the program starts up. But at startup, the framework & the
main app both are loading at 0x0, so their code overlaps. So as the
app starts up we are going to write the shared library's breakpoint
onto what will be the main executable's code. Normally this doesn't
matter, because when the framework actually loads, dyld will slide the
framework somewhere else, and we will get the load notification and
shift the breakpoint accordingly.
But if the breakpoint in the shared library is low enough that it
overlaps the dyld load commands of the application (these are stored at
the beginning of an executable or framework in Mach-O) then the
breakpoint gets written on top of the dyld load commands of the
executable as it is starting up, and the executable doesn't get as far
as loading all its shared libraries, because the load information is
corrupted. Generally it crashes somewhere in dyld like you are seeing.
The correct fix for the bug is for gdb to hold off setting breakpoints
in shared libraries till it gets the load notification for them. But
that's not going to help you much right now...
The short-term workaround for you is just to give your framework some
load address that gets it out of the way of the main executable.
Pretty much anything will do. For the other project I work on that has
lots of shared libraries, we use
-seg1addr 0xa000000
for the first framework, and the 0xb000000, etc. This doesn't seem to
collide with anything. You set this in the Other Linker Flags section
of the Framework Targets build settings. Try setting this for your
framework, and then rebuilding it, and see if you can start up again.
If this does not fix the problem, and you don't mind giving us a look
at your project, please file a bug with your project files.
Thanks,
Jim
On May 6, 2004, at 9:38 AM, Fred Leboucher wrote:
Got a really weird problem coming up today.. First the app wouldn't
load in the debugger telling me that it could not load the framework
that goes with the app (in the error msg, the name was cut at
".fr\340" instead of ".framework"). This one only occured once. I made
a Clean All/Build and retried, and then it started crashing with this
backtrace :
#0 0x8fe27624 in __dyld_strrchr ()
#1 0x8fe03970 in __dyld_get_framework_name ()
#2 0x8fe02df8 in __dyld_try_framework_search ()
#3 0x8fe0320c in __dyld_load_library_image ()
#4 0x8fe068cc in __dyld_load_images_libraries ()
#5 0x8fe02cd8 in __dyld_load_executable_image ()
#6 0x8fe01a30 in __dyld__dyld_init ()
I also set the variable DYLD_PRINT_LIBRARIES to 1, and here's what I
get :
loading libraries for
DYLD_INSERT_LIBRARIES=/Developer/Applications/Xcode.app/Contents/
PlugIns/GDBMIDebugging.pbplugin/Contents/Resources/
PBGDBIntrospectionSupport.A.dylib
loading library:
/Developer/Applications/Xcode.app/Contents/PlugIns/
GDBMIDebugging.pbplugin/Contents/Resources/
PBGDBIntrospectionSupport.A.dylib
loading libraries for image: /bin/bash
loading library: /usr/lib/libncurses.5.dylib
loading library: /usr/lib/libSystem.B.dylib
loading libraries for image:
/Developer/Applications/Xcode.app/Contents/PlugIns/
GDBMIDebugging.pbplugin/Contents/Resources/
PBGDBIntrospectionSupport.A.dylib
loading libraries for image: /usr/lib/libncurses.5.dylib
loading libraries for image: /usr/lib/libSystem.B.dylib
loading library: /usr/lib/system/libmathCommon.A.dylib
loading libraries for image: /usr/lib/system/libmathCommon.A.dylib
Temporarily disabling shared library breakpoints: 1
Running...
loading libraries for
DYLD_INSERT_LIBRARIES=/Developer/Applications/Xcode.app/Contents/
PlugIns/GDBMIDebugging.pbplugin/Contents/Resources/
PBGDBIntrospectionSupport.A.dylib
loading library:
/Developer/Applications/Xcode.app/Contents/PlugIns/
GDBMIDebugging.pbplugin/Contents/Resources/
PBGDBIntrospectionSupport.A.dylib
loading libraries for image:
/Users/fred/XDolphin/build/MyApp.app/Contents/MacOS/MyApp
Program received signal: "EXC_BAD_ACCESS".
The app launches fine on its own, but since then I can't manage to
launch in the debugger, no matter what I do...
Anyone would have any idea on how to make it work back ?
Thanks !
Fred Leboucher
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--
Jim Ingham email@hidden
Developer Tools
Apple Computer
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