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Re: [WIP] glibc: Use /lib/ld-linux-armhf.so.3 for ARM's -mfloat-abi=hard ABI.
On Thu, 26 Apr 2012, Carlos O'Donell wrote:
> (b) Detect dynamic linker used by compiler.
>
> The following new configure test detects the dynamic linker
> used by the compiler given the current set of options.
> We store the result in libc_cv_compiler_dynlinker_default
> for later use in ARM's preconfigure.
This is far too complicated. GCC isn't detecting what dynamic linker
glibc has, after all. We should simply test if the compiler predefines
__ARM_PCS_VFP, which is easy to do in the ARM preconfigure.
> I caught a couple of problems early and fixed them though,
> like not using AC_MSG_ERROR for the configure failure cases
> because you might be installing headers and not have a compiler
> capable of compiling an application yet. This does imply that
> you *might* not get the right set of headers if such headers
> changed depending on the dynamic linker selected (which
> they shouldn't).
>
> Comments?
It shouldn't (ideally) be necessary to configure glibc, or GCC, more than
once when bootstrapping. See Roland's comments at
<http://sourceware.org/ml/libc-alpha/2012-03/msg00960.html>. That means
we don't want any configure tests that will give the wrong results in a
bootstrap configuration (where you don't have a preexisting libc so can't
link things using it) - where there are existing tests we should remove
them, and we should avoid adding more.
Testing preprocessor defines is safe. Linking without -nostdlib isn't
safe in configure tests. While it looks like GCC will still pass the
default -dynamic-linker option to ld when using -nostdlib, I don't think
you should really rely on that either.
--
Joseph S. Myers
joseph@codesourcery.com