[Buildroot] [PATCH 1/2] package/Makefile.in should grab HOST_DIR headers using -isystem instead of -I.
Yann E. MORIN
yann.morin.1998 at free.fr
Mon Aug 1 22:19:17 UTC 2016
David, All,
On 2016-08-01 23:59 +0200, Yann E. MORIN spake thusly:
> On 2016-07-25 15:52 -0400, David Raeman spake thusly:
> > HOST_CFLAGS includes a search path for HOST_DIR/usr/include using -I. When
> > HOST_CFLAGS is used by a package, these flags are passed to the compiler ahead
> > of flags passed by the package's internal make system. If a package has a
> > header file with the same name as a header file in HOST_DIR, this causes the
> > toolchain to prefer the file from the system include directory because its -I
> > appears first on the command line. I believe conflicts should prefer the file
> > provided by the package. This can be accomplished by using -isystem, which is
> > more appropriate then -I for system-level include paths.
> [--SNIP--]
>
> In fact, this does not work, and the patch was reverted (for background).
>
> What we need is that gcc follows the following sequence when looking for
> headers:
>
> 1- search paths specified with -I by the package
>
> 2- search our $(HOST_DIR)/usr/include
>
> 3- search the host system /usr/include
>
> However, I can't find anything in the gcc manpage that allows to add the
> search path we need in (2).
>
> All I can see is -idirafter, to add search paths after all other
> non-system and system paths.
>
> So, probably the following would not be very far from what we'd have to
> do:
>
> -nostdinc -idirafter $(HOST_DIR)/usr/include -idirafter /usr/include
>
> This tells gcc to not look at the system include path, so it is left
> with only the paths specified by the package, and then as a fallback,
> out $(HOST_DIR)/usr/include, and then as a last resort, the host-system
> /usr/include dirs, since the last two are -idirafter:
>
> -idirafter dir
> Search dir for header files, but do it after all directories
> specified with -I and the standard system directories have
> been exhausted. dir is treated as a system include directory.
>
> Thoughts?
>
> David, would you care to see if:
>
> 1- it fixes your own problem?
No, it does not work as-is, because there is more that just /usr/include
as the standard headers search path. On my machine, gcc looks for:
$ printf "" |`gcc -print-prog-name=cc1` -v -o /dev/null >/dev/null
#include "..." search starts here:
#include <...> search starts here:
/usr/lib/gcc/x86_64-linux-gnu/5/include
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/5/include-fixed
/usr/include
End of search list.
[--SNIP--]
Adding those four makes the build suceeds, though...
But there is no simple way to get that list of search path either, so
that's a no-no for now... :-/
Furthermore, the C++ search dirs are even different:
$ printf "" |`gcc -print-prog-name=cc1` -v -o /dev/null >/dev/null
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/5
/usr/include/x86_64-linux-gnu/c++/5
/usr/include/c++/5/backward
/usr/lib/gcc/x86_64-linux-gnu/5/include
/usr/local/include
/usr/lib/gcc/x86_64-linux-gnu/5/include-fixed
/usr/include
End of search list.
Gah... :-(
Forget it, that was not a good idea... :-(
Regards,
Yann E. MORIN.
> 2- it fixes the python issues we've had with -isystem?
>
> Regards,
> Yann E. MORIN.
>
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| Yann E. MORIN | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software Designer | \ / CAMPAIGN | ___ |
| +33 223 225 172 `------------.-------: X AGAINST | \e/ There is no |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL | v conspiracy. |
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