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Re: [RFC] Do we care about binary compatibility of code produced by cross-compilers?
- From: Paolo Carlini <paolo dot carlini at oracle dot com>
- To: Ian Lance Taylor <iant at google dot com>
- Cc: libstdc++ <libstdc++ at gcc dot gnu dot org>
- Date: Sun, 24 Aug 2008 15:23:50 +0200
- Subject: Re: [RFC] Do we care about binary compatibility of code produced by cross-compilers?
- References: <48A05898.9000705@oracle.com> <m37iane6sw.fsf@google.com>
-- Ian,
For example, while I don't know offhand whether this affects binary
compatibility, it is incorrect to not test GCC_CHECK_TLS when being
built by a cross-compiler. It's true that you can't get a complete
TLS test when being built by a cross-compiler, because you can't test
the kernel. However, GCC_CHECK_TLS has a reasonable fallback for that
case: if the compiler and the binutils support TLS, it assumes that
TLS is fully supported. GCC_CHECK_TLS should be invoked
unconditionally, not only if GLIBCXX_IS_NATIVE. The same is true of
many other--though not necessarily all--tests currently controlled by
GLIBCXX_IS_NATIVE.
I tried to make some progress in mainline, please have a look again.
As regards GCC_CHECK_TLS, at the moment I don't understand the test well
enough to take an immediate action: in general I moved to unconditional
testing (e.g., both native and crosses) either tests using only
AC_TRY_COMPILE, or using GCC_TRY_COMPILE_OR_LINK, or linking only in
non-default cases, controlled by a configure-time switch.
I don't think GCC_CHECK_TLS belongs to one of those "straightforward"
cases, or, in other terms, I cannot convince myself that it's safe to
move it as-is. Can you further help with it?
Thanks,
Paolo.