[PATCH][RFC] Extend locations where to seach for Fortran pre-include.

[Martin Liška]

On 11/22/18 3:35 PM, Joseph Myers wrote:
> On Thu, 22 Nov 2018, Martin Liška wrote:
> 
>>> (Multilib suffixes on include directories for C are more or less an 
>>> implementation detail of how fixed headers are arranged in the case where 
>>> sysroot headers suffixes are used; they aren't really expected to be a 
>>> stable interface such that third-party software might install anything 
>>> using them, but I'm not sure if this preinclude is meant to come from 
>>> external software or be installed by GCC. 
>>
>> It will come from glibc-devel package, and it's expected to be installed in:
>> usr/include/finclude/ for 64-bit header
>> and /usr/include/finclude/32/ for the 32-bit header.
> 
> So, to be clear, is that
> 
> <sysroot><sysroot-headers-suffix><native-system-header-dir>/finclude/$($CC $CFLAGS $CPPFLAGS -print-multi-directory)
> 
> ?  (Where glibc would be what uses the $CC $CFLAGS $CPPFLAGS 
> -print-multi-directory to determine where to install the file.)
> 
> If so, you need to make sure that all of those pieces are properly used.
> 
> * The sysroot and headers suffix in the case of a sysrooted toolchain.  
> (Sysroot headers suffixes are for e.g. the case of a toolchain with both 
> glibc and uClibc multilibs, so needing multiple sets of headers.  Most 
> toolchains with multiple sysroots using the same libc only need a single 
> set of headers and don't use sysroot headers suffixes, only sysroot 
> suffixes (non-headers), with appropriate arrangements being made for all 
> the per-multilib headers, such as gnu/lib-names-*.h and gnu/stubs-*.h, to 
> be copied into the common include directory.)
> 
> * The native system header directory (which is /include not /usr/include 
> for GNU Hurd, for example; see config.gcc).
> 
> * Then finclude with the multilib (non-OS) suffix.
> 
> And you need to consider what's right for non-sysrooted toolchains.  If 
> native, the above is right, but without the sysroot-related components.  
> But what about a non-sysrooted cross toolchain?  Certainly using the 
> native directory would be wrong there.
> 
> Also, what's right in the multiarch directory arrangements case - should 
> it be 
> <sysroot><sysroot-headers-suffix><native-system-header-dir>/<multiarch>/finclude 
> instead?  Would one of the Debian / Ubuntu GCC maintainers like to 
> comment?
> 
> Are there corresponding versions with /usr/local/include 
> (LOCAL_INCLUDE_DIR, in general), before those with 
> NATIVE_SYSTEM_HEADER_DIR?  Even in the driver, the list of directories in 
> cppdefault.c should at least serve as a guide to which directories you 
> want to search and which get sysroots added (of course, the C++-specific 
> ones are irrelevant here).
> 

Hi.

Looks the problematic is quite complex as I can understand. I prepared a patch
that should hopefully follow advises provided.

Thoughts?
Thanks,
Martin
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