static inline in headers in C

A small function in a header must be static inline, or every including file collides.

#include <stddef.h>

static inline int clamp(int value, int low, int high) {
    if (value < low) {
        return low;
    }
    if (value > high) {
        return high;
    }
    return value;
}

static inline size_t min_size(size_t a, size_t b) {
    return (a < b) ? a : b;
}

int clamped_sum(int a, int b) {
    return clamp(a, 0, 100) + clamp(b, 0, 100);
}

How it works

1. static gives each translation unit its own copy.
2. inline invites the compiler to expand it in place.
3. This is the type-safe alternative to a function-like macro.

Keywords and builtins used here

• clamp
• clamped_sum
• if
• inline
• int
• min_size
• return
• size_t
• static

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

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