Can link a project with .exe(built using GCC) and another .dll( built using VC)?

[ChrisW67]

Maybe, it really depends a lot on the specifics. I am assuming the EXE is a Qt project.
Is the DLL a COM/ActiveX object? If so, use ActiveQt.
Is the DLL pure C functions or is it C++? If the former then you will probably have better luck.
MingW mixing compilers

[babygal]

Maybe, it really depends a lot on the specifics. I am assuming the EXE is a Qt project.
Is the DLL a COM/ActiveX object? If so, use ActiveQt.
Is the DLL pure C functions or is it C++? If the former then you will probably have better luck.
MingW mixing compilers

I do not know if DLL is a COM or ActiveX object.How do I confirm? But I only know DLL comes with a .lib(Object File Library) and other header files.
DLL is in MSVC C++ .

[ChrisW67]

Do you have to register the DLL to use it? Com/ActiveX DLLs have a bunch of related registry entries that are created by registration. Try it if you don't know:

C:\Windows\system32> regsvr32 example.dll

C:\Windows\system32> regsvr32 example.dll

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Non-COM DLLs will generate an error message.

The binary interface of C++ code differs between GCC and MSVC++ so if the DLL is straight C++ you are probably out of luck.