Socket programming in C/C++ - gcc char * warning [duplicate]

Question

Possible Duplicate:
Deprecated conversion from string constant to char * error

I'm writting a program in C/C++ which is attempting to communicate over a UDP socket.

The code I'm working on has a variable, char *servIP, which is set through an input parameter to the main function. However, I want the input parameter to be optional, so I have the code:

if(argc > 1)
    servIP = argv[1];           /* First arg: server IP address (dotted quad) */
else
    servIP = "127.0.0.1";

servIP later gets converted into a more network-usable form.

When I compile this, I get a warning saying "warning: deprecated conversion from string constant to char*".

I assume this isn't the correct way to enter that IP address; what is a better way?

Just a note that you could eventually check if the content of argv[1] is a valid IP address. — ForceMagic
– ForceMagic, Commented Oct 14, 2012 at 1:55
do you realise, that your question has nothing to do with "Socket programming", "UDP".. ? — Karoly Horvath
– Karoly Horvath, Commented Oct 14, 2012 at 3:08
Are you programming in C or in C++? They're two different languages. — Keith Thompson
– Keith Thompson, Commented Oct 14, 2012 at 3:26
problem solution, found thanks to @Karoly Horvath, is just to do: char ip[] = "127.0.0.1"; servIP = ip; — Gossamer Shadow
– Gossamer Shadow, Commented Oct 14, 2012 at 6:18

jspcal · Accepted Answer · 2012-10-14 01:37:43Z

4

declare servIP as a const char * instead of char * or, if that's not possible, strdup("127.0.0.1") (in the second case, just remember to free it later)

the effect of modifying a string literal is undefined, which is why c++ assigns the type "array of n const char" to a string literal. the compiler is warning you about the conversion from a const data type to a non-const one.

you can use std::string instead, and then when you need a C-style pointer to the underlying characters, you can use std::string::c_str().

edited Oct 14, 2012 at 1:37

answered Oct 14, 2012 at 1:26

jspcal

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