GDB complaining about missing raise.c

To do full source code debugging of the C library on Ubuntu, there are just a few steps to take:

1. Install the debuginfo version of libc6.

   It’s probably already installed – the gdb package on Ubuntu has a dependency on it – but in case it isn’t, run sudo apt install libc6-dbg.

2. Prepare the package system to download and process source code packages, if this hasn’t previously been done.

   sudo apt install dpkg-dev
   grep deb-src /etc/apt/sources.list
   

   Grep’s output should show (and there may be additional matches that we don’t need to worry about):

   deb-src http://archive.ubuntu.com/ubuntu/ bionic main restricted
   deb-src http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted
   

   If the grep shows that these deb-src lines are commented out with #:

   # deb-src http://archive.ubuntu.com/ubuntu/ bionic main restricted
   # deb-src http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted
   

   then edit /etc/apt/sources.list to remove the # at the beginning of these lines and then run sudo apt update .

3. Download the source code corresponding to the installed version of the C library.

   First, create a directory anywhere – I’ll use /opt/src here.

   Then do the following:

   cd /opt/src
   apt source libc6
   

   If the apt command gives an error message like

   E: You must put some ‘source’ URIs in your sources.list

   then my instructions in step 2 may have become outdated; post a comment here.

   When the download is complete, run this:

   find $PWD -maxdepth 1 -type d -name 'glibc*'
   

   Remember this name – it’ll be something like /opt/src/glibc-2.23

4. Determine where gdb expects to find the source code and make appropriate adjustments.

   Run gdb, have it run your program until it stops, and at the gdb prompt do this:

   (gdb) info source
   Current source file is ../sysdeps/unix/sysv/linux/raise.c
   Compilation directory is /build/glibc-KM3i_a/glibc-2.23/signal
   

   So gdb is expecting the source code to be in /build/glibc-KM3i_a/glibc-2.23 . There are two ways to fix this:

   • Move (or use a symlink) so that the source code is (or appears to be) in /build/glibc-KM3i_a/glibc-2.23 .

     or

   • Tell gdb how to substitute the correct source directory pathname:

     (gdb) set substitute-path /build/glibc-KM3i_a/glibc-2.23 /opt/src/glibc-2.23
     

   Now, go back to your frame, and gdb should show the source code line:

   (gdb) frame 1
   #1 0xb7e2fea9 in __GI_raise (sig=6) at ../sysdeps/unix/sysv/linux/raise.c:54
            return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);