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Dealing with compilers that pretend to be GCC
From: |
Ludovic Courtès |
Subject: |
Dealing with compilers that pretend to be GCC |
Date: |
Thu, 19 Jan 2012 15:24:48 +0100 |
User-agent: |
Gnus/5.110018 (No Gnus v0.18) Emacs/24.0.90 (gnu/linux) |
Hello,
A number of compilers claim to be GCC, without actually being GCC. This
has come to a point where they can hardly be distinguished–until one
actually tries to use them.
I had the following macro to determine whether plug-in support is
available:
https://gforge.inria.fr/scm/viewvc.php/trunk/m4/gcc.m4?view=markup&revision=5169&root=starpu&pathrev=5202
The macro is fairly elaborate. Yet, ICC 12.0.1 and Clang 3.4 both pass
the test, because:
- They support ‘--version’;
- They define ‘__GNUC__’, which defeats Autoconf’s
‘_AC_LANG_COMPILER_GNU’.
- They support ‘-print-file-name’, and have ‘-print-file-name=plugin’
return GCC’s (!) plug-in header directory. To that end, ICC simply
runs ‘gcc -print-file-name=plugin’, while Clang appears to be doing
some guesswork.
It turns out that ICC manages to build a working GCC plug-in, so after
all, it may be “entitled” to define ‘__GNUC__’, in a broad sense.
Conversely, Clang doesn’t support several GNU extensions, such as nested
functions, so it quickly fails to compile code.
Based on that, I modified my feature test like this:
https://gforge.inria.fr/scm/viewvc.php/trunk/m4/gcc.m4?root=starpu&r1=5169&r2=5203
I don’t see what can be done on “our” side (perhaps Autoconf’s feature
test could be strengthened, but how?), but I wanted to document this
state of affairs.
Thanks,
Ludo’.
- Dealing with compilers that pretend to be GCC,
Ludovic Courtès <=
Re: Dealing with compilers that pretend to be GCC, Joseph S. Myers, 2012/01/24