Bug#906472: horst: FTBFS in buster/sid (unable to open 'stdarg.h')

[Luc Van Oostenryck <luc.vanoostenryck@gmail.com>]

On Fri, Sep 14, 2018 at 09:45:44PM +0200, Uwe Kleine-König wrote:
> Hello,
> 
> [Cc += sparse mailing list]

Sorry for the late answer.
 
> > > Santiago Vila wrote...
> > > 
> > > > 	make -j1 check
> > > > make[1]: Entering directory '/<<PKGBUILDDIR>>'
> > > > sparse -g -O2 -fdebug-prefix-map=/<<PKGBUILDDIR>>=. -fstack-protector-strong -Wformat -Werror=format-security -std=gnu99 -Wall -Wextra -g -I. -DDO_DEBUG -I/usr/include/libnl3 *.[ch]
> > > > /usr/include/err.h:25:11: error: unable to open 'stdarg.h'
> > > 
> > > To reproduce this it's important to remove gcc-7 from the build chroot
> > > (apt purge libgcc-7-dev ; apt --purge autoremove).
> > > 
> > > Problem is, sparse appearently uses hardcoded paths and looks for
> > > stdarg.h in (among other places)

Well, sparse needs to know where it can find the system header files.
There is an option for this: -gcc-base-dir (and -multiarch-dir).
Usually you will want to use either some that are installed by your
distro or the one that match the exact GCC version you're using.

By *default*, if no -gcc-base-dir is used, sparse use the same dir
as the one used by the GCC used to compile sparse itself. It's only
this default that is hardcoded.

> > > Solution is to rebuild sparse, building horst was successful then.
> > > If this is true (please check!), the interesting question is why this
> > > wasn't a problem in earlier gcc version bumps.
> 
> I think this is a known limitation of sparse and there are three
> ways to fix this (in my order of preference):
> 
>  a) let horst use cgcc -no-compile instead of sparse; or
>  b) let sparse depend on libgcc-7-dev (or whatever provides the
>     necessary files); or
>  c) use autodetection which gcc is used and pick its files.
>
> I'm not sure if a) fixes the problem. It fixed another problem we had
> with horst's usage of sparse in the past though[1].
> 
> The downside of c) is that running this autodetection on every call to
> sparse is probably slowing down sparse a bit which isn't nice.

In case the default can't be used, like here, I think the best is
to add in your Makefile something like:
	GCC_BASE_DIR=$(shell $(CC) -print-file-name=)
	SPARSE_FLAGS= -gcc-base-dir $(GCC_BASE_DIR)
	...
		sparse $(SPARSE_FLAGS) ...

This doesn't need to be done at each invocation of sparse (but will be done
at each top-level make invocation).

Regards,
-- Luc