gdb: source code location mapping on startup

When you run gdb, you usually have to add source code directories using the “dir” command. This is okay if your code lies within a single directory, but if the code you’re debugging jumps across files in various directories, you’ll end up running “dir” several times, and this can be quite cumbersome.
The solution isn’t as simple as specifying the top-level (root) directory where your source code is checked out, because gdb won’t try to find matching source files recursively in the directory tree. gdb only checks the current directory (i.e. where you launched gdb from), and other directories specified via “dir” for matching source files.
Fortunately, there’s an elegant and simple solution to this problem:
To add directories to gdb automatically, so that you don't have to point out the source code dirs manually each time you start gdb, just specify the “substitute-path” like this in your .gdbinit file:

set substitute-path 
/sandbox/builds/appframework_dev/  /data/source/branches/appframework_dev

This tells gdb that the source files that it was initially expecting at “/sandbox/builds/appframework_dev” (which is the location of the source code on the build machine, where you got the binaries that you are debugging), are mapped to the local directory (on your test machine) at “/data/source/branches/appframework_dev”

see this relevant discussion on stackoverflow for this and other approaches to this problem

EDIT: it appears that I had already blogged this little nugget of gdb goodness last year, along with a few more interesting gdb tidbits