Object-like macros in C

A define is textual substitution, done before the compiler sees your code.

#define MAX_STARS 3
#define GREETING "welcome"
#define BUFFER_SIZE (256 * 4)

int stars_available(void) {
    int buffer[8];
    (void) buffer;
    return MAX_STARS;
}

size_t greeting_length(void) {
    return sizeof GREETING - 1;
}

int buffer_bytes(void) {
    return BUFFER_SIZE;
}

How it works

1. There is no type and no scope, only replacement.
2. An enum or const is usually the better constant.
3. Undefining and redefining is legal, which is part of the danger.

Keywords and builtins used here

• buffer_bytes
• greeting_length
• int
• return
• size_t
• sizeof
• stars_available
• void

The run, in numbers

Lines

17

Characters to type

265

Tokens

50

Three-star pace

95 tpm

At the three-star pace of 95 tokens a minute, this run takes about 32 seconds.

Type this snippet

Step 1 of 4 in Macros, step 1 of 12 in Preprocessor & headers.

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