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Re: [PATCH]: Separate target and host config files

Zack Weinberg wrote:
Nathan Sidwell <> writes:

This patch fixes the problem by adding a new '' template and
amending the configure machinery to create auto-target.h from that, and
inlude that file in 'tconfig.h'.  This allowed me to remove the #include
auto-host.h from the target side libraries.  I also uncovered a couple
of typos with the runtime checking configure processing.

If I understand the patch correctly, the definitions in auto-target.h
are a strict subset of the definitions in auto-host.h.  I'm not sure I
see the point.  Is it merely that some of those definitions are unsafe
to expose to target libraries?  If so, could you illustrate why?

Correct they are a subset. However, auto-host also contains such delights as BYTEORDER, CHAR_BIT, and various type #defines like ssize_t. It seems dangerous to expose more than the minimum necessary to the target-side files. The current situation of just including auto-host.h where it is absolutely needed is not practical going forward, as essentially all target side files include tsystem.h, which now provides definitions for runtime gcc_assert and gcc_unreachable. It requires ENABLE_RUNTIME_CHECKING to know what those should expand to.

Also, again if I understand correctly, I'd prefer that the subsetting
be done not by configure, but by a separate operation controlled from
the Makefile, e.g. by adding more special-case logic to
for tconfig.h.  This is primarily because I don't trust autoheader not
to decide it knows better, and splat a complete copy of onto, ruining all your careful subsetting.

The subsetting is done manually, by manually editing the template file (as it says in the comment therein). autoheader will only autogenerate the _first_ template mentioned in AC_CONFIG_HEADERS, as autoheader's documentation states. In this case that will remain

An alternative mechanism for creating auto-target.h would be to
grep auto-host.h for the desired #defines.  But this strikes me as
reinventing the wheel -- autoconf already has machinery to generate
a header file from a template, and that's what I've employed.

Also also, could we please *not* increase the number of files
with a confusing name relationship to their thing.h?  Call it if it must exist.

yeah, I was in a quandry about that, and I had originally named it as you suggest. But, that then makes it inconsistent with the current mapping of>auto-host.h. IMHO having a similar mapping to that was more desireable -- but there wasn't much in it :) Perhaps we should take the opportunity of renaming to and removing that confusion too! If we do that, I'd prefer to address it as a separate patch.

Let me know how you'd like to proceed


Nathan Sidwell    ::   ::     CodeSourcery LLC    ::

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