Revert "Slightly refactor stackwalk64 capture frames implementation"

This reverts commit cbd5454.

Author: jeremy-rifkin

src/unwind/unwind.hpp

@@ -7,6 +7,7 @@
 #include <vector>
 
 #ifdef CPPTRACE_UNWIND_WITH_DBGHELP
+ #define UNWIND_MAY_NEED_CONTEXT_RECORD
  #define WIN32_LEAN_AND_MEAN
  #include <windows.h>
 #endif

src/unwind/unwind_with_dbghelp.cpp

@@ -23,34 +23,6 @@ namespace detail {
     #pragma warning(push)
     #pragma warning(disable: 4740) // warning C4740: flow in or out of inline asm code suppresses global optimization
     #endif
-    void capture_context(CONTEXT& context) {
-        #if defined(_M_IX86) || defined(__i386__)
-         context.ContextFlags = CONTEXT_CONTROL;
-         #if IS_MSVC
-          __asm {
-              label:
-              mov [context.Ebp], ebp;
-              mov [context.Esp], esp;
-              mov eax, [label];
-              mov [context.Eip], eax;
-          }
-         #else
-          asm(
-              "label:\n\t"
-              "mov{l %%ebp, %[cEbp] | %[cEbp], ebp};\n\t"
-              "mov{l %%esp, %[cEsp] | %[cEsp], esp};\n\t"
-              "mov{l $label, %%eax | eax, OFFSET label};\n\t"
-              "mov{l %%eax, %[cEip] | %[cEip], eax};\n\t"
-              : [cEbp] "=r" (context.Ebp),
-                [cEsp] "=r" (context.Esp),
-                [cEip] "=r" (context.Eip)
-          );
-         #endif
-        #else
-         RtlCaptureContext(&context);
-        #endif
-    }
-
     CPPTRACE_FORCE_NO_INLINE
     std::vector<frame_ptr> capture_frames(
         std::size_t skip,
@@ -68,7 +40,31 @@ namespace detail {
         if(exception_pointers) {
             context = *exception_pointers->ContextRecord;
         } else {
-            capture_context(context);
+            #if defined(_M_IX86) || defined(__i386__)
+             context.ContextFlags = CONTEXT_CONTROL;
+             #if IS_MSVC
+              __asm {
+                  label:
+                  mov [context.Ebp], ebp;
+                  mov [context.Esp], esp;
+                  mov eax, [label];
+                  mov [context.Eip], eax;
+              }
+             #else
+              asm(
+                  "label:\n\t"
+                  "mov{l %%ebp, %[cEbp] | %[cEbp], ebp};\n\t"
+                  "mov{l %%esp, %[cEsp] | %[cEsp], esp};\n\t"
+                  "mov{l $label, %%eax | eax, OFFSET label};\n\t"
+                  "mov{l %%eax, %[cEip] | %[cEip], eax};\n\t"
+                  : [cEbp] "=r" (context.Ebp),
+                    [cEsp] "=r" (context.Esp),
+                    [cEip] "=r" (context.Eip)
+              );
+             #endif
+            #else
+             RtlCaptureContext(&context);
+            #endif
         }
         // Setup current frame
         STACKFRAME64 frame;
@@ -108,6 +104,11 @@ namespace detail {
 
         // Dbghelp is is single-threaded, so acquire a lock.
         auto lock = get_dbghelp_lock();
+        // For some reason SymInitialize must be called before StackWalk64
+        // Note that the code assumes that
+        // SymInitialize( GetCurrentProcess(), NULL, TRUE ) has
+        // already been called.
+        //
         auto syminit_info = ensure_syminit();
         HANDLE thread = GetCurrentThread();
         while(trace.size() < max_depth) {