I'm trying to initialize an array of strings in C. I want to set one of the elements of the array from a variable, but I'm getting a compiler error. What's wrong with this?
char * const APP_NAME = "test_app";
char * const array_of_strings[4] = {
APP_NAME,
"-f", "/path/to/file.txt",
NULL
};
The error is error: initializer element is not constant.
The standard distinguishes const-qualified variables and compile time constants.
Evaluating a variable (APP_NAME) is not considered to be a compile time constant in the sense of the C standard. This
char const app_name[] = "test_app";
char const*const array_of_strings[4] = {
&app_name[0],
"-f", "/path/to/file.txt",
0,
};
would be allowed, since this is not evaluating app_name but only taking its address.
Also, you always should treat string literals as if they had type char const[]. Modifying them has undefined behavior, so you should protect yourself from doing so.
warning: initialization from incompatible pointer type. Any idea?I was able to get it to compile with this syntax using gcc 4.6.3:
char* const APP_NAME = "test_app";
char* const array_of_strings[4] = {
APP_NAME,
"-f", "/path/to/file.txt",
NULL
};
You could also try casting to a const (at your own risk) if the compiler rejects everything else:
char* const APP_NAME = "test_app";
char* const array_of_strings[4] = {
(char* const)APP_NAME,
"-f", "/path/to/file.txt",
NULL
};
