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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug c++/55252] New: Caret diagnostic doesn't show useful location when macro clashes with name in system header
Date: Fri, 09 Nov 2012 18:07:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55252

             Bug #: 55252
           Summary: Caret diagnostic doesn't show useful location when
                    macro clashes with name in system header
    Classification: Unclassified
           Product: gcc
           Version: 4.8.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: redi@gcc.gnu.org


(preprocessed source doesn't show the error due to the system_header pragma)


$ cat test.cc
#define bar 1
#include "header.h"
$ cat header.h
#pragma GCC system_header
int bar = 0;
$ g++ test.cc
test.cc:1:13: error: expected unqualified-id before numeric constant
 #define bar 1
             ^

This is no help because it doesn't point you to the line in header.h that
clashes with 'bar'

Without the system_header pragma you get

test.cc:1:13: error: expected unqualified-id before numeric constant
 #define bar 1
             ^
header.h:2:5: note: in expansion of macro 'bar'
 int bar = 0;
     ^

Which at least shows both locations, although the first diagnostic is still
confusing ... are the two locations backwards?  The "expected unqualified-id
before numeric constant" should point to "int bar = 0;"