Skip to content

Instantly share code, notes, and snippets.

@mike-myers-tob
Last active June 13, 2024 15:27
Show Gist options
  • Save mike-myers-tob/9a6013124bad7ff074d3297db2c98247 to your computer and use it in GitHub Desktop.
Save mike-myers-tob/9a6013124bad7ff074d3297db2c98247 to your computer and use it in GitHub Desktop.
Steps to get GDB actually working in April 2021 on macOS (Intel x86-64 only)

Debug with GDB on macOS 11

The big reason to do this is that LLDB has no ability to "follow-fork-mode child", in other words, a multi-process target that doesn't have a single-process mode (or, a bug that only manifests when in multi-process mode) is going to be difficult or impossible to debug, especially if you have to run the target over and over in order to make the bug manifest. If you have a repeatable bug, no big deal, break on the fork from the parent process and attach to the child in a second lldb instance. Otherwise, read on.

Install GDB

Don't make the mistake of thinking you can just brew install gdb. Currently this is version 10.2 and it's mostly broken, with at least two annoying bugs as of April 29th 2021, but the big one is https://sourceware.org/bugzilla/show_bug.cgi?id=24069

$ xcode-select install  # install the XCode command-line tools
$ brew install --force --build-from-source domq/gdb/gdb  # a patched version based on 10.1

It's now installed at /usr/local/bin/gdb.

Create and Install a Self-Signed Code-Signing Certificate

  1. Start the Keychain Access application, found in /Applications/Utilities.
  2. From the Keychains list on the left, right-click on the System item and select Unlock Keychain "System".
  3. Choose Keychain Access > Certificate Assistant > Create a Certificate... from the menu.
  4. Choose a name (e.g. gdb-cert), set Identity Type to Self Signed Root, set Certificate Type to Code Signing and select the Let me override defaults. Click several times on Continue until you get to the Specify a Location For The Certificate screen, then set Keychain to System.
  5. If for some reason you create the certificate in the System keychain directly, create it in the Login keychain, then export it. You can then import it into the System keychain.
  6. Finally, using the context menu for the certificate, select Get Info, open the Trust item, and set Code Signing to Always Trust.
  7. From the Keychains list on the left, right-click on the System item and select Lock Keychain "System".
  8. You must quit the Keychain Access application and restart the system, in order to use the certificate.

Create the entitlements plist file (for macOS 10.14 and newer)

We'll call it gdb-entitlement.xml:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN"
"http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>com.apple.security.cs.allow-jit</key>
    <true/>
    <key>com.apple.security.cs.allow-unsigned-executable-memory</key>
    <true/>
    <key>com.apple.security.cs.allow-dyld-environment-variables</key>
    <true/>
    <key>com.apple.security.cs.disable-library-validation</key>
    <true/>
    <key>com.apple.security.cs.disable-executable-page-protection</key>
    <true/>
    <key>com.apple.security.cs.debugger</key>
    <true/>
    <key>com.apple.security.get-task-allow</key>
    <true/>
</dict>
</plist>

Codesign and entitle the GDB executable

$ codesign --entitlements gdb-entitlement.xml -fs gdb-cert $(which gdb)

This seems to work even though that's Homebrew's link to the actual file on disk:

% ls -la $(which gdb)
lrwxr-xr-x  1 mmyers  admin  26 Apr 28 16:16 /usr/local/bin/gdb -> ../Cellar/gdb/10.2/bin/gdb
% codesign -vvv /usr/local/Cellar/gdb/10.2/bin/gdb
/usr/local/Cellar/gdb/10.2/bin/gdb: valid on disk
/usr/local/Cellar/gdb/10.2/bin/gdb: satisfies its Designated Requirement

Finally, Run GDB

$ gdb hello_world
(gdb) break main
(gdb) run

Troubleshooting

  • GDB will not understand "fat" executables. You can "lipo -thin x86_64" them.
  • If you tried debugging with gdb, but you get a "No symbol table is loaded" error, you might need to compile programs with the -ggdb option in gcc. I didn't have this issue personally.
  • If after hitting run in gdb, you get "Starting program: /path/to/your/executable [args] [New Thread 0x2303 of process 795]" followed by a blank line which does not respond to anything, then you have hit GDB bug 24069. Check that you built the patched version from source.
@michaelschem
Copy link

@4nuG same problem. All mac chips (those starting with M) are arm and not x86_64.

@siddharth7061
Copy link

Hi I am using macOS Catalina 10.15.7
I had to create the certificate in login as it was showing error while doing it in system. How do i import it to system, please explain.

@mayakrunal
Copy link

@siddharth7061 I think you can just import it into key chain, if it's on your local laptop.

https://support.apple.com/guide/keychain-access/add-certificates-to-a-keychain-kyca2431/mac

@mayakrunal
Copy link

@ferdnyc
Copy link

ferdnyc commented Oct 21, 2022

# download the script
https://github.com/conda-forge/gdb-feedstock/blob/main/recipe/macos-codesign/macos-setup-codesign.sh

# replace the certificate name
sed -i 's/gdb-codesign/gdb-cert/g' macos-setup-codesign.sh

@hitzhangjie

Note that, at least with the current version of https://github.com/conda-forge/gdb-feedstock/blob/main/recipe/macos-codesign/macos-setup-codesign.sh, that sed command should be:

sed -i 's/gdb_codesign/gdb-cert/g' macos-setup-codesign.sh

Since the script (now?) uses an underscore instead of a dash.

Probably makes sense to do this, in fact:

sed -i 's/gdb_codesign/gdb_cert/g' macos-setup-codesign.sh

And then use the name gdb_cert instead.

@optimux
Copy link

optimux commented Nov 27, 2022

Hang issue:
If after hitting run in gdb, you get "Starting program: /path/to/your/executable [args] [New Thread 0x2303 of process 795]" followed by a blank line which does not respond to anything, then you have hit GDB bug 24069.

This problem has an easy fix, type in terminal:
echo "set startup-with-shell-off" >> ~/.gdbinit
source ~/.gdbinit

Restart gdb you'll find it's working. This issue is quite annoying, I spent weeks on this but failed. Tools must be easy to use not to keep us from working!

@optimux
Copy link

optimux commented Dec 4, 2022

Hi guys,
I just ran into a wired issue: <error reading variable: failed to get range bounds>. For variables of size 1 in local subroutines or shared from other modules, I can print its value; whereas for variables of size >1 (like 2D arrays or 1D vector), either in local subroutines or from shared modules, it says error reading variable: failed to get range bounds when I tried to print. Do you guys have any ideas? This is quite annoying.

info: macOS Monterey 12.0.1 + gdb 12.1 + intel chip + fortran90

The same code works properly on CentOS9 + gdb 10.2.

Thanks!

@phil-blain
Copy link

Hi @optimux, this looks like a general regression in GDB, not specific to macOS. If you can replicate it (using the same GDB version) on Linux, then I encourage you to report it to the GDB bug tracker, see:

@ken-salterdiazsolutions
Copy link

ken-salterdiazsolutions commented Jan 3, 2023

I'm running gdb 12.1 from brew install gdb. I have my .gdbinit file with set startup-with-shell off. I have setup Visual Studio Code to use gdb. It launches and I see this:

=thread-group-added,id="i1"
GNU gdb (GDB) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin22.1.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word".
=cmd-param-changed,param="startup-with-shell",value="off"
Warning: Debuggee TargetArchitecture not detected, assuming x86_64.
=cmd-param-changed,param="pagination",value="off"
[New Thread 0x2303 of process 42682]

and there it does nothing else. Any thoughts?

@ken-salterdiazsolutions
Copy link

ken-salterdiazsolutions commented Jan 3, 2023

Additionally, if I try to debug outside of Visual Studio Code, I get this:

GNU gdb (GDB) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
Type "show copying" and "show warranty" for details.
This GDB was configured as "x86_64-apple-darwin22.1.0".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://www.gnu.org/software/gdb/bugs/>.
Find the GDB manual and other documentation resources online at:
    <http://www.gnu.org/software/gdb/documentation/>.

For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from greetings...
Reading symbols from /Users/kensalter/repos/nim/bin/greetings.dSYM/Contents/Resources/DWARF/greetings...
(gdb) run
Starting program: /Users/kensalter/repos/nim/bin/greetings 
[New Thread 0x2703 of process 42833]

^C[New Thread 0x2403 of process 42833]
warning: unhandled dyld version (17)
Server listening on port 8080

Notice, I have to feed a Command+C to kill the shell task so that my program actually runs.

@ferdnyc
Copy link

ferdnyc commented Jan 4, 2023

@ken-salterdiazsolutions

All of the previous times "unhandled dyld version" has come up, it's been an issue of GDB just plain being out of date with the latest Apple changes to the dynamic-loading API. Whether that requires a simple version bump in a macro, or more involved changes to the code to support new/modified API features, is an open question. But if you're seeing that, it's likely you need a newer gdb... assuming a version even exists, yet, which has been patched to support dyld version 17.

@ken-salterdiazsolutions
Copy link

@ken-salterdiazsolutions

All of the previous times "unhandled dyld version" has come up, it's been an issue of GDB just plain being out of date with the latest Apple changes to the dynamic-loading API. Whether that requires a simple version bump in a macro, or more involved changes to the code to support new/modified API features, is an open question. But if you're seeing that, it's likely you need a newer gdb... assuming a version even exists, yet, which has been patched to support dyld version 17.

It is the latest I know of from brew (12.1)..anyway I think I've given up. If I run it via cmd line and use the Command+C to get to the actual program, because the program is written in Nim, the vars and function names are mangled. Was investigating if Nim would be something to have in my toolkit, but on the Mac at least it seems to be a PITA as far as debugging is concerned. I had also tried LLDB but no love there either. Ah well...thanks for the reply!

@ferdnyc
Copy link

ferdnyc commented Jan 5, 2023

@ken-salterdiazsolutions

Mmm, well, I certainly don't know a whole lot about Nim. From a quick skim online, I gather that it basically compiles down to source code in a number of different languages (C, C++, JS, etc.), but C by default. If you're seeing mangled symbols, sounds like it may be compiling to C++ (or maybe Nim does its own mangling).

You've probably seen most of these already, but...

This blog post recommends using all of these options on the nim c command line, for generating debuggable binaries:

$ nim c -d:debug --lineDir:on --debuginfo --debugger:native myprogram.nim

This documentation page also suggests including --opt:none (but that may be the default for -d:debug anyway). It sounds like --debugger:native is the really important flag.

It also looks like there are pre-made convenience wrappers available, when using gdb with Nim:

Compile this code with --debugger:native and load it to nim-gdb.

nim c --debugger:native test.nim
nim-gdb test

If you cannot find nim-gdb, you can download Nim/bin/nim-gdb and Nim/tools/nim-gdb.py from Nim repository. If you don't use nim-gdb, execute source Nim/tools/nim-gdb.py command after you run gdb. nim-gdb is a bash script that execute GDB and let GDB load Nim/tools/nim-gdb.py. And nim-gdb.py is a Python script that make GDB print Nim variables nicely.

@domq
Copy link

domq commented Jan 19, 2023

Many thanks @mike-myers-tob and all participants to this gist. I just updated the relevant Wiki page with the correct and up-to-date contents for gdb-entitlement.xml as seen above.

@Vegz78
Copy link

Vegz78 commented Jan 19, 2023

Great work!!!

@VenkyDevHub
Copy link

Great!!! It is working on my Mac. Thanks very much for this procedure.

@gpertea
Copy link

gpertea commented Aug 24, 2023

No luck here, Catalina 10.15.7, latest gdb 13.2 installed with brew, trying to debug C++ program in latest Eclipse. When I try debugging, it just runs ignoring any breakpoints I set. If I check the option to stop at "main", it does stop as the debug session starts, but in a nonsensical place, and the call stack also does not make any sense. The dreaded "unhandled dlyd version" issue might have something to do with this failure, I guess..

[New Thread 0x2803 of process 67174]
[New Thread 0x1e03 of process 67174]
[New Thread 0x2503 of process 67174]
warning: unhandled dyld version (16)

Thread 3 hit Temporary breakpoint 4.1, 0x00000001000f1f75 in ....

Same behavior no matter what compiler I use (tried: Xcode clang++ 12.0 and brew g++ 13.1)

@PrabhuUdurg
Copy link

Sonoma 14.4.1 with gdb 14.2 still the same problem as in @gpertea case above

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment