invalid conversion from 'const char*' to 'char*'
Have a code as shown below. I have problem passing the arguments.
stringstream data;
char *addr=NULL;
strcpy(addr,retstring().c_str());
retstring()
is a function that returns a string.
//more code
printfunc(num,addr,data.str().c_str());
I get the error
invalid conversion from 'const char*' to 'char*'.
initializing argument 3 of 'void Printfunc(int, char*, char*)'on argument 3 of the function
on the above line. The function is called as shown below
void Printfunc(int a, char *loc, char *stream)
please let me know if I need to change any initialization.
Well, data.str().c_str()
yields a char const*
but your function Printfunc()
wants to have char*
s. Based on the name, it doesn't change the arguments but merely prints them and/or uses them to name a file, in which case you should probably fix your declaration to be
void Printfunc(int a, char const* loc, char const* stream)
The alternative might be to turn the char const*
into a char*
but fixing the declaration is preferable:
Printfunc(num, addr, const_cast<char*>(data.str().c_str()));
string::c.str()
returns a string of type const char *
as seen here
A quick fix: try casting printfunc(num,addr,(char *)data.str().c_str())
;
While the above may work, it is undefined behaviour, and unsafe.
Here's a nicer solution using templates:
char * my_argument = const_cast<char*> ( ...c_str() );
First of all this code snippet
char *addr=NULL;
strcpy(addr,retstring().c_str());
is invalid because you did not allocate memory where you are going to copy retstring().c_str().
As for the error message then it is clear enough. The type of expression data.str().c_str() is const char * but the third parameter of the function is declared as char *. You may not assign an object of type const char * to an object of type char *. Either the function should define the third parameter as const char * if it does not change the object pointed by the third parameter or you may not pass argument of type const char *.