Can't interupt the target process after attach on Linux+GDB

[gregg-miskelly]

After attaching to a process on Linux+GDB (Ubuntu 7.7.1-0ubuntu5~14.04.2), we don't have a way of breaking into the target process.

The result of this bug is that we can't get into break state to set breakpoints, or any of the other tasks we might want. So only breakpoints set before start debugging will work.

The only way I found that we could work around this is to -

1. Configure gdb to stop on SIGINT using: handle SIGINT stop
2. Using kill from the shell to interrupt the target:
   kill -TRAP

Some of the things I tried:

1. Enabling target-async before the attach. I tried both on the command line and before issuing the command.
2. Sending Ctrl-C. My debuggee has signal handlers installed, which could be the problem, but I couldn't get this to work.

[hth313]

At the vscode-cpptools I filed the following: microsoft/vscode-cpptools#334 which may be related.

I tried browsing around in the git history, but I could not find a particular commit related to this issue, so I do not know for sure.