On Mon, 15 Jun 2015, Nathan Ridge wrote:
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?
-fabi-version=n https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html
- why do gcc 5.1 and clang 3.6 report different values?
Clang's value is likely meaningless, they copied all the macros that gcc was defining at the time of 4.2.
- is the library's behaviour (of producing a fatal runtime error upon a mismatch) appropriate?
I think it is a bad idea, it ignores -fabi-compat-version and causes trouble for users, whereas the ABI changes only affect corner cases and usually result in compilation failure, not weird runtime behaviors. Do they also check _GLIBCXX_USE_CXX11_ABI? But it is their choice, I can understand wanting to eliminate as many outside sources of bugs as possible before investigating issues. Now that g++ uses -fabi-version=0 by default, there will probably be enough pressure that they will have to remove that error (at least downgrade it to a warning), or all distributions will do that for them.
-- Marc Glisse
