Re: [PATCH] Wrong search order for #include_next

[Alexey Neyman <alex dot neyman at auriga dot ru>]

On Friday 18 March 2005 13:18, Neil Booth wrote:
> Alexey Neyman wrote:-
>> The problem arises when an #include_next directive is used from a 
>> file that was included in quotes itself. In this case, this means:
>> 
>> tst.c: #include <limits.h>
>> $GCCINC/limits.h: #include "syslimits.h"
>> $GCCINC/syslimits.h: #include_next <limits.h>
>> 
>> The problem is that the paths supplied to the 
>> cpp_set_include_chains() routine  
>> are not inserted into the directory hash. Therefore, when 
>> syslimits.h is included, a new cpp_dir entry is created and
>> prepended to the quote_include list by the make_cpp_dir() routine.
>> The resulting search path list looks like:
>>
>> [$GCCINC] --> [/usr/local/include] --> [$GCCINC] --> [/usr/include]
>> 
>> The syslimits.h file is found in the 1st entry ($GCCINC) and 
>> retains a pointer to that entry in its 'dir' field. When the
>> `#include_next <limits.h>' is attempted, the search starts at the
>> dir->next directory, which is /usr/local/include in this example.
>> Therefore, the <limits.h> is found in the 3rd entry, which is again
>> $GCCINC. 
> 
> This is intended behaviour.  Once you have #include "" the include 
> chain is prepended with the current directory, and searching starts
> there. Since that is where in the include chain it was found,
> #include_next correctly starts after that point.
> 
> The real bug is the use of "" includes in what appears to be a
> system header.  limits.h should angled includes.

Well, at least this contradicts to what 'make cpp' says. Its 
occasional user won't have knowledge of its internals, therefore I'd 
view this behavior as rather puzzling: the search path list states 
that directories dir1, dir2, dir3 are searched in that order; but 
#include_next from a file in dir2 finds the included file in dir2 
again.

And, this patch retains the prepending of directory-of-this-file to 
the search list, therefore normal quoted includes are searched from 
there. What is changed is that if such a directory that was prepended 
to the search path actually appears in either include search path 
(including in quotes, angles or both), the search for #include_next 
starts from that entry.

Regards,
Alexey.

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