TOC
Summary
This post is a note about debugging C and Objective-C code of Emacs with LLDB.
If you want info about Emacs and dap-mode, see this post:
As an example, I wrote the procedure for “step executing” that the EmacsApp does not have a mainWindow in applicationDidFinishLaunching in nsterm.m.
By the way, I used GDB at the beginning of debugging, but I couldn’t check the values of Objective-C variables. Therefore, I switched to LLDB from GDB.
Prerequisites
- macOS Big Sur (v11.6, Intel CPU)
- Xcode v13.2.1
- LLDB v1300.0.42.3
- Emacs v28.0.90 (Emacs pretest 28.0.90 is out – GNU mailing lists)
Steps
Build Emacs (C/Objective-C) with debug symbol.
./configure CFLAGS="-g3 -O0"\
--with-ns\
--with-modules\
--without-x\
--without-selinux\
--without-mail-unlink\
--without-mailhost\
--without-pop\
--without-mailutils\
--without-compress-install
make -j$(sysctl -n machdep.cpu.thread_count) bootstrap
make installLaunch lldb.
$ lldb nextstep/Emacs.app/Contents/MacOS/Emacs
(lldb) target create "nextstep/Emacs.app/Contents/MacOS/Emacs"
Current executable set to '/path/to/your/emacs/nextstep/Emacs.app/Contents/MacOS/Emacs' (x86_64).
(lldb)Set breakpoint.
(lldb) b nsterm.m:5626Run Emacs via lldb.
# `-Q` is init option for Emacs
# More detail is https://www.gnu.org/software/emacs/manual/html_node/emacs/Initial-Options.html
(lldb) run -Q
Process 60822 launched: '/path/to/your/emacs/nextstep/Emacs.app/Contents/MacOS/Emacs' (x86_64)
2022-01-01 22:07:24.890807+0900 Emacs[60822:1208222] (
)
2022-01-01 22:07:24.925930+0900 Emacs[60822:1208222] SecTaskLoadEntitlements failed error=22 cs_flags=20, pid=60822
2022-01-01 22:07:24.926053+0900 Emacs[60822:1208222] SecTaskCopyDebugDescription: Emacs[60822]/0#-1 LF=0
Process 60822 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
frame #0: 0x0000000100348d3b Emacs`-[EmacsApp applicationDidFinishLaunching:](self=0x0000000101318500, _cmd="applicationDidFinishLaunching:", notification=@"NSApplicationDidFinishLaunchingNotification") at nsterm.m:5626:4
5623 #ifdef NS_IMPL_GNUSTEP
5624 ((EmacsApp *)self)->applicationDidFinishLaunchingCalled = YES;
5625 #endif
-> 5626 [NSApp setServicesProvider: NSApp];
5627
5628 [self antialiasThresholdDidChange:nil];
5629 #ifdef NS_IMPL_COCOA
Target 0: (Emacs) stopped.Print value.
(lldb) po NSApp
<EmacsApp: 0x101318500>
(lldb) po [EmacsApp superclass]
NSApplication
(lldb) po [[EmacsApp sharedApplication] mainWindow]
nilStep-over
(lldb) n
Process 60822 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = step over
frame #0: 0x0000000100348d52 Emacs`-[EmacsApp applicationDidFinishLaunching:](self=0x0000000101318500, _cmd="applicationDidFinishLaunching:", notification=@"NSApplicationDidFinishLaunchingNotification") at nsterm.m:5628:4
5625 #endif
5626 [NSApp setServicesProvider: NSApp];
5627
-> 5628 [self antialiasThresholdDidChange:nil];
5629 #ifdef NS_IMPL_COCOA
5630 [[NSNotificationCenter defaultCenter]
5631 addObserver:self
Target 0: (Emacs) stopped.Continue Emacs.
(lldb) c
Process 60822 resuming
2022-01-01 22:17:28.303972+0900 Emacs[60822:1208222] SecTaskLoadEntitlements failed error=22 cs_flags=20, pid=60822
2022-01-01 22:17:28.304077+0900 Emacs[60822:1208222] SecTaskCopyDebugDescription: Emacs[60822]/0#-1 LF=0
2022-01-01 22:17:28.462339+0900 Emacs[60822:1208222] SecTaskLoadEntitlements failed error=22 cs_flags=20, pid=60822
2022-01-01 22:17:28.462428+0900 Emacs[60822:1208222] SecTaskCopyDebugDescription: Emacs[60822]/0#-1 LF=0
2022-01-01 22:17:28.670099+0900 Emacs[60822:1208222] MTLIOAccelDevice bad MetalPluginClassName property (null)
2022-01-01 22:17:28.720344+0900 Emacs[60822:1208222] +[MTLIOAccelDevice registerDevices]: Zero Metal services found
Quit lldb.
(lldb) q
