gdb on mac 10.9 fails with “not in executable format: File format not recognized” for 32+64 arch

Question

$ file app
app: Mach-O universal binary with 2 architectures
app (for architecture i386):    Mach-O executable i386
app (for architecture x86_64):  Mach-O 64-bit executa         


        

Answer 1

Unfortunately, the non-Apple version of GNU gdb is currently unable to debug universal (or 'fat') binaries (ones that contain both 32-bit and 64-bit executables).

One option is to use lipo to extract a single architecture and run gdb on that:

lipo -thin x86_64 -output app-x86_64 ./app

or

lipo -thin i386 -output app-i386 ./app

If you'd prefer to debug the combined executable, you could try using LLDB, or an Apple version of gdb.

Answer 2

As OP commented, using Apple's gdb will fix the problem.

Here are instructions to build Apple gdb 6.3.50.20050815-cvs from source on OS 10.9:

NOTE: You will need to install Xcode and set up a build environment. If you have Homebrew installed, run brew doctor to see if "Your system is ready to brew."

1. Download the gdb-1822 source tarball from: http://opensource.apple.com/tarballs/gdb/gdb-1822.tar.gz

2. Extract this into a temporary directory. Open a terminal and cd into gdb-1822/src.

3. Run the configure script:

   ./configure --prefix="$HOME/.local/stow/gdb-1822" --disable-debug --disable-dependency-tracking --with-system-readline
   

   (The last three configure arguments are from the homebrew-dupes formula: https://github.com/Homebrew/homebrew-dupes/blob/master/gdb.rb )

4. Run make:

   make
   make install
   

5. Follow the instructions at https://sourceware.org/gdb/wiki/BuildingOnDarwin#Creating_a_certificate to create a gdb-cert code signing certificate.

6. cd into $HOME/.local/stow/gdb-1822/bin and sign the gdb executable:

   codesign -s gdb-cert gdb
   

7. cd into $HOME/.local/stow and stow the gdb-1822 folder:

   stow gdb-1822
   

8. Add $HOME/.local/bin to your PATH and either restart the terminal or clear Bash's cache to the location of gdb:

   hash -d gdb