Create and use first-versions.h with macros for function symbol versions

[Andreas Schwab]

On Apr 21 2017, Joseph Myers <joseph@codesourcery.com> wrote:

> This patch arranges for the glibc build to generate a header
> first-versions.h that defines macros for the earliest symbol version
> in which each public symbol (GLIBC_[0-9]* symbol version, name only
> uses C identifier characters) is available.
>
> This is used in sysdeps/ieee754/ldbl-opt/math-type-macros-double.h to
> replace the manually defined LDOUBLE_*_libm_version macros for various
> functions defined using type-generic templates, the purpose of which
> is to use in LONG_DOUBLE_COMPAT tests "was this function originally
> added before glibc supported long double != double on this platform?".

This won't always be the first version of a symbol, so the first version
can be non-fitting.

Andreas.

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Andreas Schwab, schwab@linux-m68k.org
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