How can I make CDT / GDB not complain about missing glibc sources? - gdb

Question

I'm debugging this app in Eclise CDT (which is using GDB), and I'm getting the following:
... etc. ...
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Program received signal SIGINT, Interrupt.
2169 rtld.c: No such file or directory.
dl_main (phdr=<optimized out>, phnum=<optimized out>, user_entry=<optimized out>, auxv=<optimized out>) at rtld.c:2169
Temporary breakpoint 3, main (argc=3, argv=0x7fffffffd4a8) at /home/eyalroz/src/bbp-reader/src/main.cpp:104
... etc. ...
So, it looks like GDB was looking for the source file for glibc's rtld.c . I can download the sources, but - what do I do with them? Where do I put them?
(I'm using Kubuntu 16.04 Linux).

Answer 1

Here are some steps, they will work (theoretically) with any package:
Enable Sources for your package manager
I use Synaptic on XUbuntu, but you should be able to find equivalent for KUbuntu and your package manager, or edit the /etc/ files directly.
a. Open Synaptic
b. From Settings Menu -> Choose Repositories
c. Check the Source code check box.
d. Press close and reload source lists
Download source code for libc6-dev. In an empty directory, without sudo, run apt-get source libc6-dev. This will download tar file and apply all the patches for your platform. After this you should have a glibc-2.23/ (or similar) directory
In Eclipse CDT setup source lookup to map what the directory at build time of the C library was to where you have downloaded. To do this:
Step into the C Library function you want to debug (in my example I am using puts), you should end up with the source not found editor like this:
That editor shows you the build path. Press Locate File... button and browse for the specific source file where you downloaded it above. That should show you the source file.
Step 5 saved the path in the launch configuration for the containing directory. As glibc is large and contains multiple directories, you may want to apply this change to all directories. To do that:
Using the path displayed in Step 4, up until the glibc directory (/build/glibc-Qz8a69/glibc-2.23 in my example) add a path mapping globally in Eclipse CDT by:
Open Preferences -> C/C++ -> Debug -> Source Lookup Path
Press Add...
Choose Path Mapping, press OK and enter whatever name you want.
Press Add
Enter the path from step 7 in the Compilation Path and the corresponding directory on your machine in Local file system path. And press OK. It should now look like this:
Debug away.
Alternatively you can make the change just to an individual launch configuration.
Command Line GDB
You can do the same with GDB at the command line, after downloading source. Here is a trace:
$ gdb -q ./HelloSO
Reading symbols from ./HelloSO...done.
(gdb) b main
Breakpoint 1 at 0x40052a: file ../src/HelloSO.c, line 15.
(gdb) set substitute-path /build/glibc-Qz8a69/glibc-2.23 /tmp/x/glibc-2.23
(gdb) r
Starting program: /scratch/jacob/workspace/HelloSO/Debug/HelloSO
Breakpoint 1, main () at ../src/HelloSO.c:15
15 puts("!!!Hello World!!!"); /* prints !!!Hello World!!! */
(gdb) s
_IO_puts (str=0x4005c4 "!!!Hello World!!!") at ioputs.c:33
33 {
(gdb) s
35 _IO_size_t len = strlen (str);
(gdb)