On Mon, 27 Jan 2025, Kang-Che Sung wrote:
On Mon, Jan 27, 2025 at 12:18 PM <[email protected]> wrote:
+ passwd_argv[0] = (char *) "passwd";
+ passwd_argv[1] = (char *) "--";
+ passwd_argv[2] = (char *) login_name;
+ passwd_argv[3] = NULL;
The type of a string literal is already char *, so the first two don't need
the cast. You could even write it more compactly, like this:
char *passwd_argv[] = { "passwd", "--", (char *)login_name, NULL };
Technically, string literals are of type "const char *", not "char *".
Perhaps in C++ that is true, but not C. Ref C23, s6.4.5 "String literals",
For character string literals, the array elements have type char, ...
You can try a few compiler experiments if you like.
And when you assign string literals to "char *" like that,
unpredictable behavior can happen when the strings get modified by
some other function.
Yes. If they're allocated in rodata you'll likely get a SEGV.
Perhaps what you really intended is this?
const char *passwd_argv[] = { "passwd", "--", login_name, NULL };
That would be much more intuitive, readable, safer and so on, but then
you'll need a cast when pass it to the pre-const functions,
eg (char **)passwd_argv.
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