Diff below fixes p7zip (clang 6.0).
OK?
Index: patches/patch-CPP_Windows_ErrorMsg_cpp
===================================================================
RCS file: patches/patch-CPP_Windows_ErrorMsg_cpp
diff -N patches/patch-CPP_Windows_ErrorMsg_cpp
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ patches/patch-CPP_Windows_ErrorMsg_cpp 7 Apr 2018 13:11:53 -0000
@@ -0,0 +1,30 @@
+$OpenBSD$
+
+Index: CPP/Windows/ErrorMsg.cpp
+--- CPP/Windows/ErrorMsg.cpp.orig
++++ CPP/Windows/ErrorMsg.cpp
+@@ -14,15 +14,15 @@ UString MyFormatMessage(DWORD errorCode)
+ AString msg;
+
+ switch(errorCode) {
+- case ERROR_NO_MORE_FILES : txt = "No more files"; break ;
+- case E_NOTIMPL : txt = "E_NOTIMPL"; break ;
+- case E_NOINTERFACE : txt = "E_NOINTERFACE"; break ;
+- case E_ABORT : txt = "E_ABORT"; break ;
+- case E_FAIL : txt = "E_FAIL"; break ;
+- case STG_E_INVALIDFUNCTION : txt = "STG_E_INVALIDFUNCTION"; break ;
+- case E_OUTOFMEMORY : txt = "E_OUTOFMEMORY"; break ;
+- case E_INVALIDARG : txt = "E_INVALIDARG"; break ;
+- case ERROR_DIRECTORY : txt = "Error Directory"; break ;
++ case (DWORD)(ERROR_NO_MORE_FILES) : txt = "No more files"; break ;
++ case (DWORD)(E_NOTIMPL) : txt = "E_NOTIMPL"; break ;
++ case (DWORD)(E_NOINTERFACE) : txt = "E_NOINTERFACE"; break ;
++ case (DWORD)(E_ABORT) : txt = "E_ABORT"; break ;
++ case (DWORD)(E_FAIL) : txt = "E_FAIL"; break ;
++ case (DWORD)(STG_E_INVALIDFUNCTION) : txt = "STG_E_INVALIDFUNCTION";
break ;
++ case (DWORD)(E_OUTOFMEMORY) : txt = "E_OUTOFMEMORY"; break ;
++ case (DWORD)(E_INVALIDARG) : txt = "E_INVALIDARG"; break ;
++ case (DWORD)(ERROR_DIRECTORY) : txt = "Error Directory"; break ;
+ default:
+ txt = strerror(errorCode);
+ }
