This fixes the --disable-hosted-libstdcxx build so that it works with
--without-headers. Currently you need to also use --with-newlib, which
is confusing for users who aren't actually using newlib.
The AM_PROG_LIBTOOL checks are currently skipped for --with-newlib and
--with-avrlibc builds, with this change they are also skipped when using
--without-headers. It would be nice if using --disable-hosted-libstdcxx
automatically skipped those checks, but GLIBCXX_ENABLE_HOSTED comes too
late to make the AM_PROG_LIBTOOL checks depend on $is_hosted.
The checks for EOF, SEEK_CUR etc. cause the build to fail if there is no
<stdio.h> available. Unlike most headers, which get a HAVE_FOO_H macro,
<stdio.h> is in autoconf's default includes, so every check tries to
include it unconditionally. This change skips those checks for
freestanding builds.
Similarly, the checks for <stdint.h> types done by GCC_HEADER_STDINT try
to include <stdio.h> and fail for --without-headers builds. This change
skips the use of GCC_HEADER_STDINT for freestanding. We can probably
stop using GCC_HEADER_STDINT entirely, since only one file uses the
gstdint.h header that is generated, and that could easily be changed to
use <stdint.h> instead. That can wait for stage 1.
We also need to skip the GLIBCXX_CROSSCONFIG stage if --without-headers
was used, since we don't have any of the functions it deals with.
The end result of the changes above is that it should not be necessary
for a --disable-hosted-libstdcxx --without-headers build to also use
--with-newlib.
Finally, compile libsupc++ with -ffreestanding when --without-headers is
used, so that <stdint.h> will use <gcc-stdint.h> instead of expecting it
to come from libc.
libstdc++-v3/ChangeLog:
PR libstdc++/103866
* acinclude.m4 (GLIBCXX_COMPUTE_STDIO_INTEGER_CONSTANTS): Do
nothing for freestanding builds.
(GLIBCXX_ENABLE_HOSTED): Define FREESTANDING_FLAGS.
* configure.ac: Do not use AC_LIBTOOL_DLOPEN when configured
with --without-headers. Do not use GCC_HEADER_STDINT for
freestanding builds.
* libsupc++/Makefile.am (HOSTED_CXXFLAGS): Use -ffreestanding
for freestanding builds.
* configure: Regenerate.
* Makefile.in: Regenerate.
* doc/Makefile.in: Regenerate.
* include/Makefile.in: Regenerate.
* libsupc++/Makefile.in: Regenerate.
* po/Makefile.in: Regenerate.
* python/Makefile.in: Regenerate.
* src/Makefile.in: Regenerate.
* src/c++11/Makefile.in: Regenerate.
* src/c++17/Makefile.in: Regenerate.
* src/c++20/Makefile.in: Regenerate.
* src/c++98/Makefile.in: Regenerate.
* src/filesystem/Makefile.in: Regenerate.
* testsuite/Makefile.in: Regenerate.
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