How to properly debug a binary generated by `go test -c` using GDB?

Question

The go test command has support for the -c flag, described as follows:

-c  Compile the test binary to pkg.test but do not run it.
    (Where pkg is the last element of the package's import path.)

As far as I understand, generating a binary like this is the way to run it interactively using GDB. However, since the test binary is created by combining the source and test files temporarily in some /tmp/ directory, this is what happens when I run list in gdb:

Loading Go Runtime support.
(gdb) list
42      github.com/<username>/<project>/_test/_testmain.go: No such file or directory.

This means I cannot happily inspect the Go source code in GDB like I'm used to. I know it is possible to force the temporary directory to stay by passing the -work flag to the go test command, but then it is still a huge hassle since the binary is not created in that directory and such. I was wondering if anyone found a clean solution to this problem.

Answer 1

Unfortunately, this appears to be a known issue that's not going to be fixed. See this discussion:

https://groups.google.com/forum/#!topic/golang-nuts/nIA09gp3eNU

I've seen two solutions to this problem.

1) create a .gdbinit file with a set substitute-path command to redirect gdb to the actual location of the source. This file could be generated by the go tool but you'd risk overwriting someone's custom .gdbinit file and would tie the go tool to gdb which seems like a bad idea.

2) Replace the source file paths in the executable (which are pointing to /tmp/...) with the location they reside on disk. This is straightforward if the real path is shorter then the /tmp/... path. This would likely require additional support from the compiler / linker to make this solution more generic.

It spawned this issue on the Go Google Code issue tracker, to which the decision ended up being:

https://code.google.com/p/go/issues/detail?id=2881

This is annoying, but it is the least of many annoying possibilities. As a rule, the go tool should not be scribbling in the source directories, which might not even be writable, and it shouldn't be leaving files elsewhere after it exits. There is next to nothing interesting in _testmain.go. People testing with gdb can break on testing.Main instead.

Russ Status: Unfortunate

So, in short, it sucks, and while you can work around it and GDB a test executable, the development team is unlikely to make it as easy as it could be for you.