Question

Possible Duplicate:
How to get rid of deprecated conversion from string constant to ‘char*’ warnings in GCC?

I use following function from library which i cannot change:

HRESULT DynamicTag(char * pDesc, int * const pTag ); 

I use it as follows. I have created the object of the class provided by the library that implements the above function.

int tag =0;
g_pCallback->DynamicTag("MyLogger", &tag);

I am getting following warning:

warning: deprecated conversion from string constant to 'char*'

What is the best way of getting rid of above warning? I don’t want to allocate memory dynamically.

Info: I am using Vxworks6.8 compiler

Answer 1

Dealing with unknown library

When passing literals and not other const string, and you are not sure if the library is modifiying the string, is easy to create a stack allocated temporary copy of the literal in C++ (inspired by How to get rid of `deprecated conversion from string constant to ‘char*’` warnings in GCC?):

char strMyLogger[]="MyLogger";
g_pCallback->DynamicTag(strMyLogger, &tag);

Use explicit cast to work around a weak library prototype

On most compilers explicit conversions avoid warnings, like:

 g_pCallback->DynamicTag(const_cast<char *>("MyLogger"), &tag);

Note: You can use this only when you are sure the function is really never modifying the string passed (i.e. when the function could be declared as const char *, but it is not, perhaps because the library writer has forgotten to add it). An attempt to modify a string literal is an undefined behaviour and on many platforms it results in a crash. If you are not sure, you need to make a writeable copy of the string, which may be dynamically allocated or even stack allocated, when you know some upper limit for the string size.