[Bug preprocessor/52566] New: #include in c++ namespace scope doesn't work properly

[Bug preprocessor/52566] New: #include in c++ namespace scope doesn't work properly

[shihjr at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

             Bug #: 52566
           Summary: #include in c++ namespace scope doesn't work properly
    Classification: Unclassified
           Product: gcc
           Version: 4.4.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: shihjr@gmail.com


# gcc --version
gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3

3 source files: ns1.h ns2.h test.cpp

---------------------------------------------------------
ns1.h:
#pragma once
class A
{
};
---------------------------------------------------------
ns2.h:
#pragma once
class A
{
};
---------------------------------------------------------
test.cpp:
namespace NS1
{
#include "ns1.h"
}
namespace NS2
{
#include "ns2.h"
}
int main()
{
    NS2::A a;
    return 0;
}
---------------------------------------------------------

# touch *   // important step, let ns1.h and ns2.h have same modification time
# gcc test.cpp
test.cpp: In function 'int main()':
test.cpp:11: error: 'A' is not a member of 'NS2'
test.cpp:11: error: expected ';' before 'a'

# gcc -c -E test.cpp
# 1 "test.cpp"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "test.cpp"
namespace NS1
{
# 1 "ns1.h" 1

class A
{
};
# 4 "test.cpp" 2
}
namespace NS2
{

}
int main()
{
    NS2::A a;
    return 0;
}

----------------------------------------------------
The NS2::A declaration isn't included in namespace NS2

[Bug preprocessor/52566] #include in c++ namespace scope doesn't work properly

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-12 16:30:32 UTC ---
this has nothing to do with namespace scope, it's #pragma once confusing two
separate files as one

[Bug preprocessor/52566] #include in c++ namespace scope doesn't work properly

[jakub at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jakub at gcc dot gnu.org

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> 2012-03-12 17:09:37 UTC ---
You either should have different content of the two headers, or don't use
#pragma once, or you need to have different timestamps.  In order to support
symlinks/hardlinks and also lame filesystems that lack them, the preprocessor
only looks at file sizes/timestamps and content if there are multiple #pragma
once (or #import) headers.

[Bug preprocessor/52566] #include in c++ namespace scope doesn't work properly

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-14 10:46:54 UTC ---
If you want to use #pragma once the simplest solution might be to put a unique
comment in each file, with e.g. just the filename, or a description of its
purpose

[Bug preprocessor/52566] #include with #pragma once and files' contents is the same

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |terra at gnome dot org

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
*** Bug 108101 has been marked as a duplicate of this bug. ***

[Bug preprocessor/52566] #include with #pragma once and files' contents is the same

[terra at gnome dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52566

--- Comment #5 from M Welinder <terra at gnome dot org> ---
From 108101:

Note also:

# gcc -MM c.c
c.o: c.c a.h

No b.h present!

I.e., Makefiles built with this will not pick up changes to the second file.