Cannot convert argument 1 from 'const char[13] to 'char*'

Question

I am attempting to implement some TWAIN functionality into a QT project. I have opened this code from the provider and compiled it. However when I past the code into my project it wont compile.

Basically I have 3 files CommonTWAIN.h, TwainAPP.cpp, and DSMInterface.cpp.

In CommonTwain.h I define a constant I believe, called. kTWAIN_DSM_DLL_NAME

/* CommonTWAIN.h */
#ifdef TWH_CMP_MSC
  #ifdef TWH_64BIT
    #define kTWAIN_DSM_DLL_NAME "TWAINDSM.dll"
  #else
    #define kTWAIN_DSM_DLL_NAME "TWAINDSM.dll"
  #endif // #ifdef TWH_64BIT
#elif defined(TWH_CMP_GNU)
  #define kTWAIN_DSM_DLL_NAME "libtwaindsm.so"
#else
  #error Sorry, we don't recognize this system...
#endif

In TwainApp.cpp I use that constant in a function call.

/*   TwainApp.cpp   */
LoadDSMLib(kTWAIN_DSM_DIR kTWAIN_DSM_DLL_NAME)

That function calls code that is in DSMInterface.cpp defined by

/*   DSMInterface.h   */
bool LoadDSMLib(char* _pszLibName);

I get stuck with this error

However The code also provides a visual studio solution that I can open and compile. This works as expected with the same code. So I am assuming I just have something configured wrong. This is fairly out of what I am comfortable with but I do think I am missing something simple.

So far I have tried adding QMAKE_CXXFLAGS += -permissive to the project file. no luck.

Answer 1

I don't like that cast much. I'm sure it will work fine in practise (well, almost sure) but I don't like it on principle.

Instead, I would do something like this:

std::string libname = kTWAIN_DSM_DIR kTWAIN_DSM_DLL_NAME;
LoadDSMLib(libname.data());

If you ❤️ QString then you can probably use that instead.

Answer 2

you should be able to cast it away:

LoadDSMLib((char*)(kTWAIN_DSM_DIR kTWAIN_DSM_DLL_NAME))

as long as the function isn't trying to modify the string it should be fine.