Windows API: Strange behaviour after calling GetModuleFileNameExA

[Regan Heath]

This is totally whacky...  using the code posted below I get the 
following output:

a 4
b 2000
c
d
e 883C00 300
f 883C00 300
g 883C00 300
h 884FF0 4296896

The output for both g and h are written with:
writefln("h %p %d", processFileName.ptr, processFileName.length);

The line between the two which causes this behaviour is
processFileName = "Unknown".dup;

PID of 4 is of course "System".

Removing the call to GetModuleFileNameExA prevents the problem.

My guess is that GetModuleFileNameExA is corrupting the stack somehow, 
perhaps the implib didn't correctly convert the dll to a lib.  I used:

implib /noi /system psapi.lib C:\windows\system32\psapi.dll

The full code:

import std.stdio;
import std.c.windows.windows;

extern (Windows) HANDLE OpenProcess(uint dwDesiredAccess, BOOL 
bInheritHandle, uint dwProcessId);

extern (C)
{
   BOOL EnumProcesses(DWORD* pProcessIds, DWORD cb, DWORD* pBytesReturned);
   DWORD GetModuleFileNameExA(HANDLE hProcess, HMODULE hModule, char* 
fileName, uint size);
}

void main(char[][] args)
{
   char[] processFileName;
   uint[] processIds;
   uint[] processIds2;
   uint byteCount;

   processIds.length = 256;

   int ret = EnumProcesses(processIds.ptr, 
processIds.length*uint.sizeof, &byteCount);
   if(ret!=0)
   {
     processIds.length = byteCount/uint.sizeof;
     processIds2 = processIds.dup;

     foreach(i, pid; processIds)
     {
       if(pid==0) continue;
       writefln("a %d", pid);
       HANDLE hProcess = OpenProcess(0x410 /* QueryInformation | VMRead 
*/, false, pid);
       writefln("b %d", cast(int)hProcess);
       if(cast(int)hProcess>0)
       {
         writefln("c");
         processFileName.length = 300;
         writefln("d");
         uint namelength = 0;
         writefln("e %p %d", processFileName.ptr, 
processFileName.length);
         namelength = GetModuleFileNameExA(hProcess, cast(HMODULE)0, 
processFileName.ptr, processFileName.length);
         writefln("f %p %d", processFileName.ptr, 
processFileName.length);
         if (namelength == 0)
         {
           writefln("g %p %d", processFileName.ptr, processFileName.length);
           processFileName = "Unknown".dup;
           writefln("h %p %d", processFileName.ptr, processFileName.length);
         }
         else
         {
           writefln("i");
           processFileName.length = namelength;
           writefln("j");
         }
         break;
         writefln("%d. (%d) => %s", i, pid, processFileName);
         CloseHandle(hProcess);
       }
     }
   }
}