Add a little USE_DIA for anyone building on VS express to disable

* The DIA SDK is only available on VS pro and above, but it's only needed
  to be able to resolve symbols in the pdblocate helper program. So we add
  a little define that makes pdblocate instantly quit, and then symbol
  resolution just fails.

pdblocate/pdblocate.cpp

@@ -22,6 +22,7 @@
  * THE SOFTWARE.
  ******************************************************************************/
 
+#define USE_DIA 1
 
 #include <windows.h>
 #include <string>
@@ -34,15 +35,21 @@
 #include <assert.h>
 
 #include <dbghelp.h>
-#include <dia2.h>
-#include <atlconv.h>
-
 #include <shlobj.h>
 
 #include <vector>
 using std::vector;
 using std::wstring;
 
+#if USE_DIA
+// if you don't have dia2.h (only included with VS pro and above)
+// set USE_DIA to 1. Everything will compile but symbol resolution
+// for callstacks will not work.
+// If you need this, you could always drop in a pre-compiled pdblocate
+// from a normal build as this file/project changes very rarely.
+#include <dia2.h>
+#include <atlconv.h>
+
 // must match definition in callstack.h
 struct AddrInfo
 {
@@ -475,4 +482,10 @@ int WINAPI wWinMain( __in HINSTANCE hInstance, __in_opt HINSTANCE hPrevInstance,
 
 	CloseHandle(pipe);
 	return 0;
-}
+}
+#else
+int WINAPI wWinMain(__in HINSTANCE hInstance, __in_opt HINSTANCE hPrevInstance, __in LPWSTR lpCmdLine, __in int nShowCmd)
+{
+	return 2;
+}
+#endif

renderdoc/os/win32/win32_callstack.cpp

@@ -433,6 +433,8 @@ void Win32CallstackResolver::OpenPdblocateHandle()
 
 void *Win32CallstackResolver::SendRecvPipeMessage(wstring message)
 {
+	if(pdblocatePipe == NULL) return NULL;
+
 	DWORD written = 0;
 	DWORD msgLen = (DWORD)message.length()*sizeof(wchar_t);
 	BOOL success = WriteFile(pdblocatePipe, message.c_str(), msgLen, &written, NULL);
@@ -541,6 +543,9 @@ Win32CallstackResolver::Win32CallstackResolver(char *moduleDB, size_t DBSize, ws
 
 	OpenPdblocateHandle();
 
+	if(pdblocatePipe == NULL)
+		return;
+
 	// loop over all our modules
 	for(char *end = moduleDB + DBSize;
 		moduleDB < end;