Google C++ coding style, no exceptions rule. What about multithreading?

It should be noted that Google's style guide does not not preclude the handing of exceptions rather the throwing of exceptions. I.e. deal with the problem, but don't make it any worse by throwing more exceptions.

In the case of re-entering a non-recursive mutex: that is clearly a programmer error rather than some unexpected bolt from the blue. The exception should be allowed to propagate up to the calling code so that it can be seen and dealt with as a bug. It should be noted that the Google Test framework does not rely on exceptions, but it can certainly catch and report them.

While Google's style guide takes an extreme position, there is no doubt that exceptions can highly problematic when writing reusable libraries. For example, we found developing with WinCE 6.0 that exceptions got sliced on re-throwing and on ARM platforms couldn't be reliably thrown across DLL boundaries. In addition, catching an exception could take several milliseconds, so they definitely shouldn't be used for non-exceptional circumstances (i.e. 'expected' errors) where real-time performance is required. The clue's in the name really.

The practices in Google's style guide dates back to the early nineties of the previous century, when threads were rather exotic beasts. As such, it doesn't make sense to wonder how that style and threads would mix. If you use "modern" (21st century) techniques like threads, you don't use Google's style guide and vice versa.

IIRC the reason that Google does not use exceptions is that much of their codebase is not exception safe, and they cannot afford to rewrite it.

From their site:

On their face, the benefits of using exceptions outweigh the costs, especially in new projects. However, for existing code, the introduction of exceptions has implications on all dependent code. If exceptions can be propagated beyond a new project, it also becomes problematic to integrate the new project into existing exception-free code. Because most existing C++ code at Google is not prepared to deal with exceptions, it is comparatively difficult to adopt new code that generates exceptions.

Given that Google's existing code is not exception-tolerant, the costs of using exceptions are somewhat greater than the costs in a new project. The conversion process would be slow and error-prone. We don't believe that the available alternatives to exceptions, such as error codes and assertions, introduce a significant burden.

Our advice against using exceptions is not predicated on philosophical or moral grounds, but practical ones. Because we'd like to use our open-source projects at Google and it's difficult to do so if those projects use exceptions, we need to advise against exceptions in Google open-source projects as well. Things would probably be different if we had to do it all over again from scratch.

Personally speaking I much prefer function return codes than exceptions. But regardless of one's own preferences or coding styles, the important thing is to catch problems where they occur, don't let them propagate, persist or cause mayhem.

What I do, especially during development, is on detecting any sort of error in any sort of thread I get the process to freeze itself. On Linux I raise the SIGSTOP signal. The benefit of that is that I can then attach with a debugger and see the whole process in all its broken glory.