• QAston (8/8) Jul 16 2013 I'd like to dynamically load procedures from a dll in my app. To
• Adam D. Ruppe (34/34) Jul 16 2013 I'm looking at the dmd source now...
• QAston (12/17) Jul 16 2013 Thank you for the reply!

"QAston" <qaston gmail.com> writes:

I'd like to dynamically load procedures from a dll in my app. To 
load a symbol from a DLL i need it's mangled name. D currently 
offers .mangleof which I currently use to generate the name. It 
works very good, but only for short symbols. Is there any way to 
get the final mangled name of a symbol during compilation, or 
maybe there's some documentation describing how compression is 
done (code'd be fine too)? http://dlang.org/abi.html doesn't 
cover the compression scheme.

"Adam D. Ruppe" <destructionator gmail.com> writes:

I'm looking at the dmd source now...

The compression is done in the backend, file cgobj.c

The conditions are:


#define LIBIDMAX 128
     if (len > LIBIDMAX)
     {
         // Attempt to compress the name
         name2 = id_compress(name, len);
  // snip
         if (len2 > LIBIDMAX)            // still too long
         {
             /* Form md5 digest of the name and store it in the
              * last 32 bytes of the name.
              */

// snip impl, open the source to see specific details




/******************************************
  * Compress an identifier.
  * Format: if ASCII, then it's just the char
  *      if high bit set, then it's a length/offset pair
  * Returns:
  *      malloc'd compressed identifier
  */

char *id_compress(char *id, int idlen)
{



The implementation, same source file, looks like it compresses by 
looking for longest duplicate strings and then removes them, 
using the offset instead.



The reason I snipped the implementations here is the backend is 
under a more restrictive license so I don't want to get into 
copying that. But with just what I've said here combined with 
guess+check against dmd's output it might be enough to do a clean 
room implementation.



Or if Walter can give us permission to copy/paste this into a D 
file we could use id directly.

"QAston" <qaston gmail.com> writes:

On Tuesday, 16 July 2013 at 13:58:10 UTC, Adam D. Ruppe wrote:
 The reason I snipped the implementations here is the backend is 
 under a more restrictive license so I don't want to get into 
 copying that. But with just what I've said here combined with 
 guess+check against dmd's output it might be enough to do a 
 clean room implementation.

Thank you for the reply!

My current clean room implementation is limited to:

const(char)* mangledSymbol(alias symbol)()
{
     static assert(((symbol.mangleof) ~ "\0").length < 128, "long 
names won't be available in a library!");
     return ((symbol.mangleof) ~ "\0").ptr;
}

as it turned out i_didn't_need_that_descriptive_names. I'm 
posting it here, so maybe it'll be easier for some people to 
follow the currently bumpy road of DLLs in D :)