Add an option to silence OutputDebugString output (#88)

Some applications (MSYS compilers, MiKTeX) output a lot of distracting
information via OutputDebugString(). Add a flag to catchsegv to silence
it.

README.md

@@ -157,6 +157,7 @@ Here's the how to use it:
       -z           write minidumps
       -Z DIRECTORY write minidumps to specified directory
       -H           use debug heap
+      -q           silence messages from OutputDebugString
 
 ## Frequently Asked Questions
 

src/catchsegv/catchsegv.cpp

@@ -151,7 +151,8 @@ Usage(void)
           "  -m           ignore modal dialogs\n"
           "  -z           write minidumps\n"
           "  -Z DIRECTORY write minidumps to specified directory\n"
-          "  -H           use debug heap\n",
+          "  -H           use debug heap\n"
+          "  -q           silence messages from OutputDebugString\n",
           stderr);
 }
 
@@ -264,7 +265,7 @@ wmain(int argc, wchar_t **argv)
 
     bool debugHeap = false;
     while (1) {
-        int opt = getoptW(argc, argv, L"?1dhHmt:zZ:v");
+        int opt = getoptW(argc, argv, L"?1dhHmt:zZ:vq");
 
         switch (opt) {
         case L'h':
@@ -295,6 +296,9 @@ wmain(int argc, wchar_t **argv)
             debugOptions.minidump = true;
             debugOptions.minidumpDir = optarg;
             break;
+        case L'q':
+            debugOptions.no_debug_string = true;
+            break;
         case L'?':
             if (optopt == L'?') {
                 Usage();

src/common/debugger.cpp

@@ -736,6 +736,7 @@ DebugMainLoop(void)
                 lprintf("OUTPUT_DEBUG_STRING PID=%lu TID=%lu\n", DebugEvent.dwProcessId,
                         DebugEvent.dwThreadId);
             }
+            if (debugOptions.no_debug_string) break;
 
             pProcessInfo = &g_Processes[DebugEvent.dwProcessId];
 

src/common/debugger.h

@@ -31,6 +31,7 @@ struct DebugOptions {
     const wchar_t *minidumpDir = nullptr;
     HANDLE hEvent = nullptr; // Signal an event after process is attached
     DWORD dwThreadId = 0;    // Resume thread after process is attached
+    bool no_debug_string = false; // Silence OutputDebugString messages
 };
 
 EXTERN_C DebugOptions debugOptions;