Dejagnu: use -isystem to include system header files.

[Nick Clifton]

Hi Richard,

>> Or maybe 
>>builtins-config.h could include say <stdio.h> rather than <limits.h> so 
>>that it would pickup the newlib version and not the gcc version ?

> That might be OK for this case, but I'm not sure if will solve the
> problem generally.

I have confirmed that using <stdio.h> in place of <limits.h> does fix 
the unexpected failures.

Is there actually a general problem ?  The issue seems to be which 
version of <limits.h> is included by a test case using the dejagnu test 
harness.  If we include the newlib version then tests that use strict 
ANSI parsing will fail.  If we include the version in the gcc build 
directory then tests that assume that <limits.h> has come from newlib 
will fail.

It seems to me that using -isystem to include header files in the newlib 
include directories is the correct thing to do.  They are system header 
files after all.  Assuming that you can determine whether you are going 
to link with a C-library created by newlib by #include'ing <limits.h> 
seems dodgy to me.  Using <stdio.h> instead of <limits.h> is a 
workaround, but really the testcases ought to provide some weak aliases 
for the missing functions and then the _NEWLIB_VERSION check would be 
unnecessary.  (It would limit the tests to only being run by targets 
which support weak aliases but I do not consider this to be a serious 
restriction).

> I think the gcc/include directory must be added implicitly from the -B
> option.  It would appear that these add -isystem type include
> directories, so it might be just a matter of ordering the -B and
> -isystem options appropriately.

But - how would this help in the situation where -ansi and -pedantic 
have been specified as well.  In those cases we do not want to get the 
limits.h file from newlib.

Cheers
   Nick