Thread overview
[Issue 6132] New: extern (C) Silently Ignored Within D Classes
Jun 09, 2011
Braxton Sherouse
Jun 26, 2011
Braxton Sherouse
Nov 26, 2011
dawg@dawgfoto.de
Nov 26, 2011
dawg@dawgfoto.de
Nov 29, 2011
dawg@dawgfoto.de
June 09, 2011
http://d.puremagic.com/issues/show_bug.cgi?id=6132

           Summary: extern (C) Silently Ignored Within D Classes
           Product: D
           Version: D2
          Platform: x86
        OS/Version: Mac OS X
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: nobody@puremagic.com
        ReportedBy: sherouse@email.virginia.edu


--- Comment #0 from Braxton Sherouse <sherouse@email.virginia.edu> 2011-06-09 09:17:03 PDT ---
Overview:

I'm running DMD32 v2.053 on Mac OS X 10.6.7 and found the following inconsistency in name mangling:

====
extern(C) int clock(); // is mangled to _clock

class Sprocket {
  extern(C) int clock(); // is mangled to __D4test8Sprocket5clockMUZi:
}
====

Expected Results:

The compiler should either:
1) mangle the declaration according to the C conventions by cause of the
"extern (C)", or:
2) emit a compilation error because C doesn't have classes.

Actual Results:

The declaration is silently compiled according to the D conventions.

Additional Information:

While either solution would be welcomed, I'm working in context where solution 1 would save a lot of effort; I'm generating language/library bindings at compile time through the use of template metaprogramming. The code builds a (more robust) interface in D, and is just using the extern (C) to declare C functions that will later be linked in from other libraries.

Maybe it would be possible for the compiler to allow this syntax when there is no function body, but fail when there is??


Many thanks!
-braxton

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--- Comment #1 from Braxton Sherouse <sherouse@email.virginia.edu> 2011-06-25 19:41:29 PDT ---
Another peculiarity to add:

class Sprocket {
    extern (C) static int clock(); // not added to the symbol table!
}

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dawg@dawgfoto.de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dawg@dawgfoto.de


--- Comment #2 from dawg@dawgfoto.de 2011-11-26 08:54:58 PST ---
The latter happens when you don't reference that function.

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--- Comment #3 from dawg@dawgfoto.de 2011-11-26 11:40:56 PST ---
*** Issue 7005 has been marked as a duplicate of this issue. ***

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--- Comment #4 from dawg@dawgfoto.de 2011-11-29 08:59:07 PST ---
Actually one needs to note, that extern(C) is not ignored for the calling
convention. It is only ignored for the mangling and the hidden this argument.
It even results in different delegate types for extern(C) and extern(D)
methods.

So on a struct method extern(C) behaves as __cdecl but not as extern(C).

A clean cut would be to disallow extern(C/Pascal/Windows) on structure level except for static methods.

If there were a real need for declaring the calling convention than that should become a different construct.

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