Re: testsuite: introduce hostedlib effective target

[Jonathan Wakely <jwakely@redhat.com>]

On Wed, 8 Nov 2023 at 15:48, Jonathan Wakely <jwakely@redhat.com> wrote:
>
> On Wed, 8 Nov 2023 at 15:30, Alexandre Oliva <oliva@adacore.com> wrote:
> >
> > On Nov  7, 2023, Jonathan Wakely <jwakely@redhat.com> wrote:
> >
> > > An alternative approach for the g++ testsuite would be to provide a
> > > set of dummy headers for the non-freestanding ones, so that all the
> > > hosted-only headers are provided by the testsuite itself, but consist
> > > of a single line:
> >
> > > #error not available in freestanding
> >
> > > Then match on that and XFAIL. So the individual tests themselves
> > > wouldn't need the dg-skip-if added to them, they would just
> > > automatically XFAIL if they use a hosted-only header.
> >
> > *nod*.  That wouldn't cover all the circumstances, alas: there are tests
> > that fail in freestanding mode not because of headers, but because
> > -fcontracts (currently?) links libstdc++exp in, and that library is not
> > even built in freestanding mode.
>
> Hmm, yes, that seems like a bug. Either we should provide
> libstdc++exp.a for freestanding builds (with a simplified contract
> violation handler that doesn't print to stdout), or the front end
> should not add -lstdc++exp when -ffreestanding is used (which would
> require teh user, or the testsuite in your case, to provide a custom
> contract violation handler), or it should be an error to use
> -fcontracts and -ffreestanding together.
>
> The libstdc++-v3/src/experimental/contract.cc file *already* supports
> freestanding, we just don't actually build it for freestanding. We can
> do that.

Which might be as simple as:

--- a/libstdc++-v3/src/Makefile.am
+++ b/libstdc++-v3/src/Makefile.am
@@ -34,14 +34,13 @@ backtrace_dir = libbacktrace
else
backtrace_dir =
endif
-
-experimental_dir = experimental
else
filesystem_dir =
backtrace_dir =
-experimental_dir =
endif

+experimental_dir = experimental
+
## Keep this list sync'd with acinclude.m4:GLIBCXX_CONFIGURE.
SUBDIRS = c++98 c++11 c++17 c++20 c++23 \
       $(filesystem_dir) $(backtrace_dir) $(experimental_dir)