common: Don't abort StackWalk when StackFrame.AddrFrame.Offset is zero.

For code without frame pointer EBP might have any value, including zero.

This change allows to get at least the first entry of the stack when that
happens.

Fixes #29.

TODO.md

@@ -7,6 +7,7 @@
 
   - https://github.com/gcc-mirror/gcc/tree/master/libbacktrace
   - http://www.nongnu.org/libunwind/
+  - http://blog.reverberate.org/2013/05/deep-wizardry-stack-unwinding.html
 
 - Generate gdb core dumps
 

src/common/log.cpp

@@ -257,10 +257,6 @@ dumpStack(HANDLE hProcess, HANDLE hThread,
         )
             break;
 
-        // Basic sanity check to make sure  the frame is OK.  Bail if not.
-        if (StackFrame.AddrFrame.Offset == 0)
-            break;
-
         if (MachineType == IMAGE_FILE_MACHINE_I386) {
             lprintf(
                 "%08lX %08lX %08lX %08lX",
@@ -309,11 +305,9 @@ dumpStack(HANDLE hProcess, HANDLE hThread,
             dumpSourceCode(szFileName, dwLineNumber);
         }
 
-        if (StackFrame.AddrStack.Offset < PrevFrameStackOffset) {
-            break;
-        }
-
-        if (StackFrame.AddrPC.Offset == 0xBAADF00D) {
+        // Basic sanity check to make sure  the frame is OK.  Bail if not.
+        if (StackFrame.AddrStack.Offset < PrevFrameStackOffset ||
+            StackFrame.AddrPC.Offset == 0xBAADF00D) {
             break;
         }