Re: Testing for GCC-like attributes and compiler switches

[Andrew W. Nosenko]

2010/10/15 Václav Haisman <address@hidden>:
> Hi.
>
> I am having difficulty testing for compiler features like
> __declspec(dllimport) and switches like -Wall or -Werror.
>
> The problem has started like this. I wanted to test compiler for
> __declspec(dllimport) (for Windows) and if that fails for
> __attribute__((visibility("default"))) (for *nix/GCC). With GCC this works
> because it does support both, it supports __declspec(dllimport) even outside
> Windows. But with e.g. Clang, this fails. Clang accepts the code of the
> test-case with just warning like:
>
> "conftest.cpp:20:12: warning: 'dllexport' attribute ignored"
>
> The test-case passes but the compiler does not support the feature.

Can you inspect the resulting object file somehow (sorry, I'm not a
Windows guru)?  For example by trying to use result like the
program-customer intended to do.  I.e. in the case of windows try to
build trivial dll, the program-user and link them together (and,
possible, run)?

>
> I thought I could "fix" this by trying to test for -Werror first and giving
> it to the compiler for the test-case. However there is the problem with
> detecting/collecting -Werror equivalent switches for all the various
> compilers. Before I started with that, I have noticed the Sun Studio C++
> compiler happily accepts -Wall (the test for it passes) even though it warns
> that it does not know such option. So this method is useless.
>
> How is one supposed to test these things with autoconf?
>
> It seems to me that the only truly workable option is to fall back to
> deciding the flags and features of a given compiler from combination of
> platform, compiler name and compiler version. Am I right or am I missing
> something, some technique or something else?
>

-- 
Andrew W. Nosenko <address@hidden>