Enable wxStackWalker in MinGW64 builds

This class can be used even without SEH, provided debug help API is available,
so just make wxUSE_STACKWALKER dependent on wxUSE_DBGHELP instead of
unconditionally disabling it if SEH support is not available.

docs/changes.txt

@@ -74,6 +74,7 @@ wxGTK:
 
 wxMSW:
 
+- Enable wxStackWalker in MinGW64 builds.
 - Fix crash when using wxCHMHelpController() in 64 bit builds (Xlord2).
 - Fix MDI menu display after failure to create a child frame (troelsk).
 

include/wx/msw/chkconf.h

@@ -38,6 +38,14 @@
 #   endif
 #endif /* !defined(wxUSE_CRASHREPORT) */
 
+#ifndef wxUSE_DBGHELP
+#   ifdef wxABORT_ON_CONFIG_ERROR
+#       error "wxUSE_DBGHELP must be defined"
+#   else
+#       define wxUSE_DBGHELP 1
+#   endif
+#endif /* wxUSE_DBGHELP */
+
 #ifndef wxUSE_DC_CACHEING
 #   ifdef wxABORT_ON_CONFIG_ERROR
 #       error "wxUSE_DC_CACHEING must be defined"
@@ -146,9 +154,6 @@
 
 #    undef wxUSE_CRASHREPORT
 #    define wxUSE_CRASHREPORT 0
-
-#    undef wxUSE_STACKWALKER
-#    define wxUSE_STACKWALKER 0
 #endif /* compiler doesn't support SEH */
 
 #if defined(__GNUWIN32__)
@@ -292,6 +297,14 @@
 #endif  /* !wxUSE_DYNAMIC_LOADER */
 
 #if !wxUSE_DYNLIB_CLASS
+#   if wxUSE_DBGHELP
+#       ifdef wxABORT_ON_CONFIG_ERROR
+#           error "wxUSE_DBGHELP requires wxUSE_DYNLIB_CLASS"
+#       else
+#           undef wxUSE_DBGHELP
+#           define wxUSE_DBGHELP 0
+#       endif
+#   endif
 #   if wxUSE_DC_TRANSFORM_MATRIX
 #       ifdef wxABORT_ON_CONFIG_ERROR
 #           error "wxUSE_DC_TRANSFORM_MATRIX requires wxUSE_DYNLIB_CLASS"
@@ -383,6 +396,22 @@
 #   endif
 #endif /* wxUSE_ACTIVITYINDICATOR */
 
+#if wxUSE_STACKWALKER && !wxUSE_DBGHELP
+    /*
+        Don't give an error in this case because wxUSE_DBGHELP could be 0
+        because the compiler just doesn't support it, there is really no other
+        choice than to disable wxUSE_STACKWALKER too in this case.
+
+        Unfortunately we can't distinguish between the missing compiler support
+        and explicitly disabling wxUSE_DBGHELP (which would ideally result in
+        an error if wxUSE_STACKWALKER is not disabled too), but it's better to
+        avoid giving a compiler error in the former case even if it means not
+        giving it neither in the latter one.
+     */
+    #undef wxUSE_STACKWALKER
+    #define wxUSE_STACKWALKER 0
+#endif /* wxUSE_STACKWALKER && !wxUSE_DBGHELP */
+
 #if !wxUSE_THREADS
 #   if wxUSE_FSWATCHER
 #       ifdef wxABORT_ON_CONFIG_ERROR

interface/wx/stackwalk.h

@@ -25,13 +25,18 @@
     class from it and override this method.
 
     This class will not return anything except raw stack frame addresses if the
-    debug information is not available. Under Win32 this means that the PDB file
+    debug information is not available. Under Microsoft Windows this means that
-    matching the program being executed should be present.
+    the PDB file matching the program being executed should be present.
     Note that if you use Microsoft Visual C++ compiler, you can create PDB files
     even for the programs built in release mode and it doesn't affect the program
     size (at least if you don't forget to add @c /opt:ref option which is suppressed
     by using @c /debug linker option by default but should be always enabled for
-    release builds).
+    release builds). If your compiler doesn't provide a direct way of
+    generating PDB files but does produce debug information in the older "Code
+    View" format or compatible, which is the case for MinGW, you can use @c
+    cv2pdb tool available at https://github.com/rainers/cv2pdb to create PDB
+    for your binaries which will work well when using this class.
+
     Under Unix, you need to compile your program with debugging information
     (usually using @c -g compiler and linker options) to get the file and line
     numbers information, however function names should be available even without it.

src/msw/stackwalk.cpp

@@ -31,8 +31,7 @@
 #include "wx/stackwalk.h"
 
 #include "wx/msw/debughlp.h"
-
+#include "wx/msw/seh.h"
-#if wxUSE_DBGHELP
 
 // ============================================================================
 // implementation
@@ -103,6 +102,8 @@ void wxStackFrame::OnParam(wxSYMBOL_INFO *pSymInfo)
     m_paramTypes.Add(wxEmptyString);
     m_paramNames.Add(pSymInfo->Name);
 
+    wxString value;
+
     // if symbol information is corrupted and we crash, the exception is going
     // to be ignored when we're called from WalkFromException() because of the
     // exception handler there returning EXCEPTION_CONTINUE_EXECUTION, but we'd
@@ -111,22 +112,23 @@ void wxStackFrame::OnParam(wxSYMBOL_INFO *pSymInfo)
 #ifdef _CPPUNWIND
     try
 #else
-    __try
+    wxSEH_TRY
 #endif
     {
         // as it is a parameter (and not a global var), it is always offset by
         // the frame address
         DWORD_PTR pValue = m_addrFrame + pSymInfo->Address;
-        m_paramValues.Add(wxDbgHelpDLL::DumpSymbol(pSymInfo, (void *)pValue));
+        value = wxDbgHelpDLL::DumpSymbol(pSymInfo, (void *)pValue);
     }
 #ifdef _CPPUNWIND
     catch ( ... )
-#else
-    __except ( EXCEPTION_EXECUTE_HANDLER )
-#endif
     {
-        m_paramValues.Add(wxEmptyString);
     }
+#else
+    wxSEH_IGNORE
+#endif
+
+    m_paramValues.Add(value);
 }
 
 BOOL CALLBACK
@@ -306,6 +308,8 @@ void wxStackWalker::WalkFromException(size_t maxDepth)
 
 void wxStackWalker::Walk(size_t skip, size_t maxDepth)
 {
+    // We use it as a proxy for SEH support here.
+#if wxUSE_ON_FATAL_EXCEPTION
     // to get a CONTEXT for the current location, simply force an exception and
     // get EXCEPTION_POINTERS from it
     //
@@ -323,72 +327,38 @@ void wxStackWalker::Walk(size_t skip, size_t maxDepth)
         // never executed because the above expression always evaluates to
         // EXCEPTION_CONTINUE_EXECUTION
     }
-}
+#else // !wxUSE_ON_FATAL_EXCEPTION
+    // This code is based on frames.cpp from Edd Dawson's dbg library
+    // (https://bitbucket.org/edd/dbg/) which is distributed under Boost
+    // Software License.
 
-#else // !wxUSE_DBGHELP
+    CONTEXT ctx;
+#ifdef __WIN64__
+    RtlCaptureContext(&ctx);
+#else // Win32
+    // RtlCaptureContext() is not implemented correctly for x86 and can even
+    // crash when frame pointer is omitted, don't use it.
+    wxZeroMemory(ctx);
+    ctx.ContextFlags = CONTEXT_CONTROL;
 
-// ============================================================================
+    #ifdef __GNUC__
-// stubs
+        DWORD regEip, regEsp, regEbp;
-// ============================================================================
 
-// ----------------------------------------------------------------------------
+        asm volatile ("call 1f\n\t" "1: pop %0" : "=g"(regEip));
-// wxStackFrame
+        asm volatile ("movl %%esp, %0" : "=g"(regEsp));
-// ----------------------------------------------------------------------------
+        asm volatile ("movl %%ebp, %0" : "=g"(regEbp));
 
-void wxStackFrame::OnGetName()
+        ctx.Eip = regEip;
-{
+        ctx.Esp = regEsp;
-}
+        ctx.Ebp = regEbp;
+    #else
+        #error Missing implementation of RtlCaptureContext()
+    #endif
+#endif // Win64/32
 
-void wxStackFrame::OnGetLocation()
+    WalkFrom(&ctx, skip, maxDepth);
-{
-}
-
-bool
-wxStackFrame::GetParam(size_t WXUNUSED(n),
-                       wxString * WXUNUSED(type),
-                       wxString * WXUNUSED(name),
-                       wxString * WXUNUSED(value)) const
-{
-    return false;
-}
-
-void wxStackFrame::OnParam(wxSYMBOL_INFO * WXUNUSED(pSymInfo))
-{
-}
-
-void wxStackFrame::OnGetParam()
-{
-}
-
-// ----------------------------------------------------------------------------
-// wxStackWalker
-// ----------------------------------------------------------------------------
-
-void
-wxStackWalker::WalkFrom(const CONTEXT * WXUNUSED(pCtx),
-                        size_t WXUNUSED(skip),
-                        size_t WXUNUSED(maxDepth))
-{
-}
-
-void
-wxStackWalker::WalkFrom(const _EXCEPTION_POINTERS * WXUNUSED(ep),
-                        size_t WXUNUSED(skip),
-                        size_t WXUNUSED(maxDepth))
-{
-}
-
-#if wxUSE_ON_FATAL_EXCEPTION
-void wxStackWalker::WalkFromException(size_t WXUNUSED(maxDepth))
-{
-}
 #endif // wxUSE_ON_FATAL_EXCEPTION
-
-void wxStackWalker::Walk(size_t WXUNUSED(skip), size_t WXUNUSED(maxDepth))
-{
 }
 
-#endif // wxUSE_DBGHELP/!wxUSE_DBGHELP
-
 #endif // wxUSE_STACKWALKER