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Re: questions about some branches

Dmitry Malichenko wrote:
> Could you please help me with my questions about branches:
> 1) archer-pmuldoon-exception-rewind-master
> Purpose: Recover from fatal signals delivered via C++ exceptions in
> an inferior function call
> Question: What signals are meant here? Could you please describe an example?

This patch addresses undesirable behaviour in an inferior function call when a C++ exception is raised in that call. As GDB constructs a single "dummy-frame" for the inferior function call, it can prevent the unwinder from finding an out-of-frame C++ exception handler if an exception is raised in that call. The basic result then is that the C++ default exception handler is called -- which calls abort(). This signal is delivered to the inferior and terminated. As an out-of-frame handler can legitimately handle a C++ exception, and as the dummy-frame environment prevents the unwinder from locating any out-of-frame handlers, this behaviour is wrong. This patch prevents that by detecting calls to the default handler in an inferior function call, and if so detected pops the stack and restores context of the inferior to before the call (preventing termination).


void foo ()
   throw 1;

void bar ()
      foo ();
   catch (...)
      cout << "oops";

In GDB, if you were to do this:

print foo()

The inferior would be terminated, as the unwinder would not be able to find an exception handler for the throw 1. The result is the inferior is terminated.

BTW I submitted this patch upstream just last week

> There are also some general questions:
>  - Had somebody merged the branches mentioned above together?

I believe Jan has merged several for the Fedora 11 release. But he can better answer there.

> - What is the difference between Master and Archer branch?

I think Archer branch is defunct, and master tracks GDB upstream (when someone updates it from upstream)

> - Is it supposed to merge Archer with GDB (main branch) in future?

The intent is to get all branches merged upstream in the future. Several are in process now, and as more mature they will be too.

Hope this helps!


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