[vbox-dev] Help with BSTR and PCRTUTF16

Ribhi Kamal rbhkamal at gmail.com
Mon Apr 15 09:06:08 PDT 2013


Hi all,
I'm making a DLL wrapper around vboxmanage using Visual Studio 2010. For
some reason VS gives me error C2664/C2440 when it is trying to convert from
BSTR to PCRTUTF16.
1>C:\vboxbuild\virtualbox\latest\src\include\VBox/com/Guid.h(112): error
C2664: 'RTUuidFromUtf16' : cannot convert parameter 2 from 'BSTR' to
'PCRTUTF16'
1>          Types pointed to are unrelated; conversion requires
reinterpret_cast, C-style cast or function-style cast
1>C:\vboxbuild\virtualbox\latest\src\include\VBox/com/Guid.h(198): error
C2440: '<function-style-cast>' : cannot convert from 'RTUTF16 [37]' to
'com::Bstr'
1>          No constructor could take the source type, or constructor
overload resolution was ambiguous

I worked around that by using the casings below. But I was wondering why
compiling vboxmanage doesn't produce the same errors. I tried to make my
compile options match the vbox build options as much as possible but I'm
sure I missed something. Below is are my options used to compile part of
the project:

/Zi /nologo /W3 /WX-
/O2 /Oy-
/Gm- /EHsc /MD /GS
/fp:precise
/Zc:wchar_t
/Zc:forScope-
/GR
-wd4065 -wd4996 -wd4250
/Fp"Release\VboxCom.pch" /Fa"Release\" /Fo"Release\"
/Fd"Release\vcWindows7.1SDK.pdb" /Gd /analyze- /errorReport:queue
 /D "__WIN__" /D "RT_OS_WINDOWS" /D "_WIN32_WINNT=0x0501" /D "WIN32" /D
"__WIN32__" /D "RT_ARCH_X86" /D "__X86__" /D "_X86_" /D "_LIB" /D "VBOX" /D
"VBOX_OSE" /D "VBOX_WITH_64_BITS_GUESTS" /D "IN_RING3" /D "UNICODE" /D
"NDEBUG=1" /D "_REENTRANT" /D "_UNICODE"

Any help would be greatly appreciated. Below are the castings that I had to
make (V4.2.12):

--------------------------- include/VBox/com/Guid.h
---------------------------
index c55d69d..01884d2 100644
@@ -109,7 +109,7 @@ public:
     Guid(const Bstr &that)
     {
         int rc = !that.isEmpty()
-               ? ::RTUuidFromUtf16(&mUuid, that.raw())
+               ? ::RTUuidFromUtf16(&mUuid, (PCRTUTF16)that.raw())
                : VERR_INVALID_UUID_FORMAT;
         if (RT_FAILURE(rc))
             ::RTUuidClear(&mUuid);
@@ -195,7 +195,7 @@ public:

         RTUTF16 buf[RTUUID_STR_LENGTH];
         ::RTUuidToUtf16(&mUuid, buf, RTUUID_STR_LENGTH);
-        return Bstr(buf);
+        return Bstr((CBSTR)buf);
     }

     bool isEmpty() const

------------- src/VBox/Frontends/VBoxManage/VBoxManageDebugVM.cpp
-------------
index 5901c53..72addfe 100644
@@ -87,7 +87,7 @@ static RTEXITCODE handleDebugVM_GetRegisters(HandlerArg
*pArgs, IMachineDebugger
                     size_t cchMaxName  = 8;
                     for (size_t i = 0; i < aBstrNames.size(); i++)
                     {
-                        size_t cchName = RTUtf16Len(aBstrNames[i]);
+                        size_t cchName =
RTUtf16Len((PCRTUTF16)aBstrNames[i]);
                         if (cchName > cchMaxName)
                             cchMaxName = cchName;
                     }

------------------------ src/VBox/Main/glue/string.cpp
------------------------
index 9865af5..51af313 100644
@@ -179,7 +179,7 @@ void Utf8Str::copyFrom(CBSTR a_pbstr)
                 && vrc != VERR_NO_MEMORY)
             {
                 /* ASSUME: input is valid Utf-16. Fake out of memory
error. */
-                AssertLogRelMsgFailed(("%Rrc %.*Rhxs\n", vrc,
RTUtf16Len(a_pbstr) * sizeof(RTUTF16), a_pbstr));
+                AssertLogRelMsgFailed(("%Rrc %.*Rhxs\n", vrc,
RTUtf16Len((PCRTUTF16)a_pbstr) * sizeof(RTUTF16), a_pbstr));
             }

             m_cch = 0;
@@ -221,7 +221,7 @@ HRESULT Utf8Str::copyFromEx(CBSTR a_pbstr)
                 && vrc != VERR_NO_MEMORY)
             {
                 /* ASSUME: input is valid Utf-16. Fake out of memory
error. */
-                AssertLogRelMsgFailed(("%Rrc %.*Rhxs\n", vrc,
RTUtf16Len(a_pbstr) * sizeof(RTUTF16), a_pbstr));
+                AssertLogRelMsgFailed(("%Rrc %.*Rhxs\n", vrc,
RTUtf16Len((PCRTUTF16)a_pbstr) * sizeof(RTUTF16), a_pbstr));
             }

             m_cch = 0;

-- 
-- Ribhi
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