lib.d

import core.demangle : demangle;
import core.stdc.string: strlen;

extern(C) int demangle_symbol(const(char*) mangled, char* buffer, size_t bufferLength)
{
    if (mangled == null) return 0;
    auto ret = demangle( cast(char[]) mangled[0 .. strlen(mangled)], buffer[0 .. bufferLength] );
    buffer[ret.length] = 0;
    return 1;
}

makefile

build:
	dmd -c lib.d
	dmd -oflibd_demangle.so lib.o -shared

install:
	cp libd_demangle.so /usr/lib/