__GXX_ABI_VERSION: 1002 vs. 1008

[Nathan Ridge]

Hi,

I recently ran into an issue related to two compilers giving different values
for __GXX_ABI_VERSION [1].

The two compilers were gcc 5.1, which reported '1008', and clang 3.6, which
reported '1002'.

The issue is that a library (wxWidgets) produces a fatal runtime error if there
is a mismatch between the __GXX_ABI_VERSION of the compiler used to
build the library, and the compiler used to build the application using the
library.

What I'd like to know is:
  - what exactly does __GXX_ABI_VERSION signify?
  - why do gcc 5.1 and clang 3.6 report different values?
  - is the library's behaviour (of producing a fatal runtime error upon a
    mismatch) appropriate?

Thanks,
Nate

[1] http://thread.gmane.org/gmane.comp.lib.wxwidgets.general/83315