Re: [pph] Make libcpp symbol validation a warning (issue5235061)

[Diego Novillo <dnovillo at google dot com>]

On 11-10-13 17:55 , Gabriel Charette wrote:

> I'm not sure exactly how you skip headers already parsed now (we
> didn't used to when I wrote this code and that was the only problem
> remaining in the line_table (i.e. duplicate entries for guarded
> headers in the non-pph compile)), but couldn't you count the number of
> skipped entries and assert (line_table->used - used_before) +
> numSkipped == expected_in) ?

The problem is that the compilation process of foo.h -> foo.pph may 
generate different line tables than a compile that includes foo.pph. 
For instance,

foo.h:
#include "1.pph"
#include "2.pph"
#include "3.pph"

foo.cc:
#include "2.pph"
#include "foo.pph"


When we compile foo.h, the line table incorporates the effects of 
including 2.pph, and that's what we save to foo.pph.  However, when 
compiling foo.cc, the first thing we do is include 2.pph, so when 
processing the include for foo.pph, we will completely skip over 2.pph.

That's why we cannot really have the same line table that we had when we 
generated foo.pph.


Diego.