CODEWITHSUNDEEP
c++visual-studio-2010opencvlinkercalling-convention
user1595522
user1595522

Reputation: 21

Why is visual studio 2010 looking for __thiscall rather than __cdecl calling conventions?

Overall I am trying to link an opencv test program with the opencv libraries I compiled using 64-bit visual studio 2010 professional. An example error is:

1>webcamtest.obj : error LNK2001: unresolved external symbol "public: virtual bool __thiscall cv::VideoCapture::isOpened(void)const " (?isOpened@VideoCapture@cv@@UBE_NXZ)

The question is why __thiscall, when opencv_highui249.dll which it is linked with contains

Symbol name  : ?isOpened@VideoWriter@cv@@UEBA_NXZ (public: virtual bool __cdecl cv::VideoWriter::isOpened(void)const )

__cdecl makes sense, which suggests that the library is built correctly. When linking the test program, opencv_highui249.dll is being searched, so the build flags appear to be correct, but apparently I am missing something?

Upvotes: 2

Views: 1682

Answers (3)

mkaes
mkaes

Reputation: 14119

Are you sure you used x64 libraries?
Microsoft reduced the calling conventions in x64. See here. Basically everything is now __fastcall.
The compiler can still use __thiscall but it is ignored(MSDN link). So your test program is fine but your library looks wrong.

Upvotes: 1

Necrolis
Necrolis

Reputation: 26171

__thiscall is the default for class member functions in MSVC, you either need to compile OpenCV with the same settings, or explicitly use __cdecl in the header definitions.

Upvotes: 0

AshleysBrain
AshleysBrain

Reputation: 22591

__thiscall is the default calling convention in VS for member functions of classes. Perhaps the header files are missing the __cdecl specifier, or the compile flags are incorrectly set so a relevant #define for it isn't being set.

Upvotes: 0

Related Questions