CODEWITHSUNDEEP
c++debugginggdb
Praxeolitic
Praxeolitic

Reputation: 24089

Saving and restarting a paused gdb session

My understanding is that gdb can monitor the complete state of a running program. Can I save a gdb session that is paused at a breakpoint and resume the session later?

My first attempt was simply generating a core dump in a first gdb session that was paused at a breakpoint and then using the core dump to start a second gdb session.

Saving core file in gdb

This resulted in the following error.

Program terminated with signal SIGTRAP, Trace/breakpoint trap.

So breakpoint information is inserted into the program state, interesting. On my second attempt I did the same but this time I added the same breakpoint to the second session as were in the first session.

Getting gdb to save a list of breakpoints?

Still, I get the same error.

Can I save and restart a gdb session? If so, how?

I don't think this is directly relevant but I'm also getting this warning.

warning: core file may not match specified executable file.

Is gdb simply stating that such a thing is possible in general or does gdb believe this may have happened in the running session? I'm confident that the same executable that produced the core dump is being run under gdb.

Edit: For anyone else who comes along, this question: Save a process' memory for later use? adds to Mats Petersson's answer and links to this article: http://blogs.msdn.com/b/oldnewthing/archive/2004/04/20/116749.aspx which is an interesting read. The linked question also has the suggestion of wrapping the process up in a VM.

Upvotes: 6

Views: 2918

Answers (1)

Mats Petersson
Mats Petersson

Reputation: 129464

I doubt that will ever work. Handles for files and any other resources (semaphores, shared memory, serial ports, network connections and lots of other things) that the program has opened/created will be lost when you save the core-file. You can inspect it, but you can't "continue". A core-file is simply a copy of all the memory that original program was using. Anything else is "lost" when the program terminates. In other words, a core-file will only be useful to inspect things later on, but you can't run, step or continue in a core-file debug session. Only "look at things". And if you can't execute, breakpoints won't really work either... ;)

Upvotes: 5

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