Re: compiler standards (and/or min gcc version) supported with installedheaders ?

[Andreas Jaeger <aj at suse dot com>]

Here're some minor changes. Please review whether the language itself is 
clear,

Andreas

* glibc needs a recent GCC compiler version to build itself (right now
  at least 4.3 required, 4.6 or newer recommended)

* Userland applications and libraries that use glibc's headers and
  libraries can be build by a variety of compilers with the following
  notes:

  - The installed headers should work with any compiler that:
    * supports at least ISO C 90 (or C++98)
    * supports the type "long long"
  - GCC version 2.95.3 is the oldest compiler supported in general
    (for some more recent hardware architectures a more recent
    compiler will be needed)
  - Compiler dependend code needs to be protected by proper feature
    test macros. For example the various GCC __builtin_X functions can
    be used but need to be properly guarded.
  - The glibc header files might include special optimizations for
    newer compiler versions which might not be available for older
    compilers
  - The header files for glibc use GCC 4.3 as baseline for
    optimizations
  - Support for other compilers besides GCC might need extra patches
    which are welcome to be submitted for inclusion glibc
  - For headers shared with gnulib, other conditions do apply (the
    requirements from gnulib to support even older compilers)

To support different compilers, we would ideally not test - as today -
for a specific GCC version but for a specific feature.

So, instead of __GNUC_PREREQ(x,y) to check for a specific version in
some header file, the advise is to add a macro to features.h, like
__GLIBC_HAVE_BUILTIN_COMPLEX and use that - and that macro definition
is dependend on compiler versions.

--
 Andreas Jaeger aj@{suse.com,opensuse.org} Twitter/Identica: jaegerandi
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