Propagating a C++ exception through C code

Question

Hello everyone,
I wrote an XML parser using expat for a project I'm working on, and I've set up the callbacks to use C++. If the document is missing attributes on certain tags, it throws an exception. However, the exception does not propagate through the expat calls on the stack; instead, terminate() is called. So I have two questions:
- Are functions with C linkage implicitly defined as throw () when used in C++ on OS X?
- What's the common way to get around this problem?
I should also note that this problem only occurs on OS X; it works fine on GNU/Linux.
Here's some simple example code that demonstrates the issue:
http://pastebin.com/m3c791e93
Thanks,
Rob

Answer 1

Rob Hoelz wrote:
In this case, GNU/Linux may be a mess and/or wrong, but it also happens to be the primary platform for my application. OS X happens to be a close second. =D
It doesn't matter. It is still wrong. You should code to correctness rather than popularity. How do you know this "feature" won't get fixed in Linux one day. It would be better to specify '-fexceptions' if you need it. There will be no harm done if this option is redundant on Linux.
While applying -fexceptions may be a perfect solution for my simple example, I don't know if it's entirely feasible for my application. If I were to do this, I'd have to distribute Expat with my application and compile it with the appropriate changes. I suppose my reluctance to do so has come from relying on the package management facilities present in GNU/Linux for so long, and maybe I just need to get into a different mindset when targeting OS X.
You can always link expat as a static library. It is tiny and I doubt you would even notice it was there. If you don't really need a true SAX parser, you could use one of the other XML libraries.
It seems that the -fexceptions option is used when compiling Expat with the traditional configure/make/make install cycle if GCC is the compiler. So apparently the problem is not OS X or OS X's version of GCC, but rather the distribution of Expat that I have on my machine.
It is a Linux issue, not an expat issue. I tried your code on Linux without expat and without '-fexceptions'. It worked as you said it would. Now, "trying it on Linux" really means nothing. Each individual Linux box is essentially its own, unique OS. If you need exceptions in expat, you need to compile your own expat with '-fexceptions' and link it as a static library. It is pretty painless. Otherwise, you risk random failure one some machine at some point in the present or future.