On Thu, 12 Nov 2020 at 15:39, Bill Schmidt via Gcc <gcc@gcc.gnu.org> wrote:
>
> Hi! I'm working on a project where it's desirable to generate a
> target-specific header
> file while building GCC, and install it with the rest of the target-specific
> headers
> (i.e., in lib/gcc/<target>/11.0.0/include). Today it appears that only those
> headers
> listed in "extra_headers" in config.gcc will be placed there, and those are
> assumed to
> be found in gcc/config/<target>. In my case, the header file will end up in
> my build
> directory instead.
>
> Questions:
>
> * Has anyone tried something like this before? I didn't find anything.
> * If so, can you please point me to an example?
> * Otherwise, I'd be interested in advice about providing new infrastructure
> to support
> this. I'm a relative noob with respect to the configury code, and I'm
> sure my
> initial instincts will be wrong. :)
I don't know how relevant it is to your requirement, but libstdc++
creates a target-specific $target/bits/c++config.h header for each
multilib target, but it installs them alongside the rest of the C++
library headers, not in lib/gcc/<target>/.
It's done with a bunch of shell commands that takes the
autoconf-generated config.h file, combines it with a template file
that's in the source repo (libstdc++-v3/include/bits/c++config) and
then modifies it with sed. See the ${host_builddir}/c++config.h target
in libstdc++-v3/include/Makefile.am for the gory details. The other
make targets below it (for gthr-single.h and gthr-posix.h) are also
target-specific.
Those headers are listed in the ${allcreated} variable which is a
prerequisite of the all-local target, and then in the install target
they get copied into place.
