C Control Strings?

[tj9413]

I know that in other languages such as Java when I use System.out.println(); and I put a variable inside of it like an int that holds the number 22 it will print 22 to the console.

In C if I do the same thing with printf(); I need to specify the type in the string such as printf("%d", n); I also know that Java has its own printf function.

What I am trying to get at here is how the C control String works compared to other languages such as Java where you don't have to provide the type identifier in the System.out.println(); and it automatically recognizes the variable is an int.

Is this part of C's way of efficiency and does it not actually check the type and rely's on the programmer to understand the type they are providing?

[grumpy]

There is no means in standard C for a function to recognise the type of arbitrary arguments without assistance. Similarly, C does not support function overloading (two functions of the same name but different argument types, where the arguments passed by the caller determine which version is called).

It is not related to "C's way of efficiency", except possibly in the sense of keeping compilers as simple as possible, and able to be ported to more operating systems than most other languages.

[c99tutorial]

Is this part of C's way of efficiency and does it not actually check the type and rely's on the programmer to understand the type they are providing?

With some compilers like GCC, the compiler can do some checking on the printf format strings and arguments at compile time if you turn on warnings. E.g. writing printf("%d", x) would issue a warning if x is actually a pointer to an int.

With C this type of checking is normally done at compile time.

[whiteflags]

Not using a format string even when you can get away with it (like when you want to print a string by itself) is dangerous because you could fall victim to a format string attack.

[grumpy]

With some compilers like GCC, the compiler can do some checking on the printf format strings and arguments at compile time if you turn on warnings. E.g. writing printf("%d", x) would issue a warning if x is actually a pointer to an int.

With C this type of checking is normally done at compile time.

That's not what the OP is asking about. The question is why it is not possible for the compiler to deduce the required format from the type of the actual value supplied. For example, printf(2) would produce formatted int, printf(2.5) would produce a formatted float, printf('a') would output a single char -- all without the need for a format string to tell printf() what the arguments are.