www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - link to C++ function in a namespace whose name is a D keyword

reply Carl Sturtivant <sturtivant gmail.com> writes:
Hello,

 From D I want to call e.g.

/* C++ prototype */
namespace ns {
     int try(int x);
}

without writing a C or C++ wrapper.

Presumably the following D doesn't work, because it doesn't 
mangle the name as if it's in the namespace ns.

pragma(mangle, "try") extern(C++, ns) int try_(int x);

So how to I get correct mangling here?
Jan 06
next sibling parent =?UTF-8?Q?Ali_=c3=87ehreli?= <acehreli yahoo.com> writes:
On 01/06/2016 10:35 AM, Carl Sturtivant wrote:
 Hello,

  From D I want to call e.g.

 /* C++ prototype */
 namespace ns {
      int try(int x);
 }

 without writing a C or C++ wrapper.

 Presumably the following D doesn't work, because it doesn't mangle the
 name as if it's in the namespace ns.

 pragma(mangle, "try") extern(C++, ns) int try_(int x);

 So how to I get correct mangling here?
This looks like an oversight to me. I tried the following workaround but it uses D mangling scheme: import core.demangle; // PROBLEM: No way of saying "mangle C++ name". pragma(mangle, mangle!(int function(int))("ns::body")) extern(C++, ns) int body_(int x); void main() { assert(ns.body_(42) == 42); } And yes, 'try' is a C++ keyword as well; so I moved to 'body. :) Ali
Jan 06
prev sibling next sibling parent Alex Parrill <initrd.gz gmail.com> writes:
On Wednesday, 6 January 2016 at 18:35:07 UTC, Carl Sturtivant 
wrote:
 Hello,

 From D I want to call e.g.

 /* C++ prototype */
 namespace ns {
     int try(int x);
 }

 without writing a C or C++ wrapper.

 Presumably the following D doesn't work, because it doesn't 
 mangle the name as if it's in the namespace ns.

 pragma(mangle, "try") extern(C++, ns) int try_(int x);

 So how to I get correct mangling here?
Isn't try a C++ keyword though? Wouldn't that make it impossible to use in an identifier?
Jan 06
prev sibling parent Jacob Carlborg <doob me.com> writes:
On 2016-01-06 19:35, Carl Sturtivant wrote:
 Hello,

  From D I want to call e.g.

 /* C++ prototype */
 namespace ns {
      int try(int x);
 }

 without writing a C or C++ wrapper.

 Presumably the following D doesn't work, because it doesn't mangle the
 name as if it's in the namespace ns.

 pragma(mangle, "try") extern(C++, ns) int try_(int x);

 So how to I get correct mangling here?
A really ugly workaround is: 1. Declare a extern(C++) function in the "ns" namespace with the same length as the name you want, "foo" for example extern (C++, ns) { int foo(int x); } 2. Print the mangling of the function pragma(msg, foo.mangleof); // __ZN2ns3fooEi on OS X 3. Replace "foo" with the name you actually want, "try" in this case __ZN2ns3fooEi -> __ZN2ns3tryEi 4. Use pragma(mangle) to set the mangled name pragma(mangle, "__ZN2ns3tryEi") extern (C++) int try_(int x); -- /Jacob Carlborg
Jan 06