Use the native Windows way to determine the stacktrace

Note: as we target MINGW here, we still want to look up the symbols via
the DWARF method (the native Windows way would be to call the
SymFromAddr() function, but that would require .pdb files which MINGW
does not produce).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

Author: dscho

backtrace.c

@@ -96,6 +96,43 @@ unwind (struct _Unwind_Context *context, void *vdata)
   return _URC_NO_REASON;
 }
 
+#if NATIVE_WIN32_STACKTRACE
+static int win32_unwind(struct backtrace_data *bdata)
+{
+  static int initialized;
+  static USHORT (*RtlCaptureStackBackTrace)(ULONG, ULONG, PVOID*, PULONG);
+  void *pcs[62];
+  int i, count;
+
+  if (!initialized) {
+    HMODULE kernel32 =
+      LoadLibraryExW(L"kernel32.dll", NULL, LOAD_LIBRARY_SEARCH_SYSTEM32);
+    if (kernel32)
+      RtlCaptureStackBackTrace =
+        (void *)GetProcAddress(kernel32, "RtlCaptureStackBackTrace");
+    initialized = 1;
+    if (!RtlCaptureStackBackTrace)
+      return -1;
+  }
+
+  count = RtlCaptureStackBackTrace(2,
+    sizeof(pcs) / sizeof(pcs[0]), pcs, NULL);
+  for (i = 0; i < count; i++) {
+    uintptr_t pc = (uintptr_t)pcs[i];
+
+    if (!bdata->can_alloc)
+      bdata->ret = bdata->callback (bdata->data, pc, NULL, 0, NULL);
+    else
+      bdata->ret = backtrace_pcinfo (bdata->state, pc, bdata->callback,
+                                     bdata->error_callback, bdata->data);
+    if (bdata->ret != 0)
+      return _URC_END_OF_STACK;
+  }
+
+  return _URC_NO_REASON;
+}
+#endif
+
 /* Get a stack backtrace.  */
 
 int
@@ -124,6 +161,9 @@ backtrace_full (struct backtrace_state *state, int skip,
       bdata.can_alloc = 1;
     }
 
+#if NATIVE_WIN32_STACKTRACE
+  if (win32_unwind(&bdata) < 0)
+#endif
   _Unwind_Backtrace (unwind, &bdata);
   return bdata.ret;
 }

internal.h

@@ -56,6 +56,12 @@ POSSIBILITY OF SUCH DAMAGE.  */
 # endif
 #endif
 
+#if defined(__WIN32__) && !defined(__MSYS__) && !defined(__CYGWIN__)
+#define NATIVE_WIN32_STACKTRACE 1
+#else
+#define NATIVE_WIN32_STACKTRACE 0
+#endif
+
 #ifndef HAVE_SYNC_FUNCTIONS
 
 /* Define out the sync functions.  These should never be called if