@thomasanderson, feel like taking a look at this?

I reproduced this on 14.04. I also saw that `info line chrome_main.cc:50` did work as expected. So perhaps there's something weird going on with when when symbols are loaded in the component builds, or something?

For me with Goobuntu 14.04 and gdb 7.9-gg19, "info line CompositedLayerMapping.cpp:0" works correctly.  "info line v8.cpp:0" does print garbage.  My first guesses would be bugs in gdb, gdb's handling of split-dwarf, or in the toolchain's emission of split-dwarf.  However, I tried disabling split-dwarf (gn arg use_debug_fission=false) and it did not change the behavior.  So my second guesses are bugs in gdb and the toolchain's emission of DWARF independent of split-dwarf.

Note that it's normal to not see all the symbols when using gdb "cold", i.e. before you start the program.  The program has to be running for gdb to know about all the shared objects (components).  So for me "No source file named CompositedLayerMapping.cpp." does happen before starting the program, but it finds that file fine once the program has started.  Try e.g. "b _start" or "b main" and then "run".

I also note that there is no source file named "v8.cpp".  There is a "v8.cc" and "i lin v8.cc:0" works fine.  I don't know why gdb's error message is replaced with garbage for the particular case of "i lin v8.cpp:0" when other nonexistent file names give the proper error message.  So my third guess is some obscure gdb bug in the error case but no actual problem because I haven't seen (reproduced) a failure of something that actually ought to work.

Thanks, mcgrathr@. It sounds like there's not really anything for us to do here other than punt this upstream to gdb.