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Asked: 2026-06-14T12:32:01+00:00

When reading nginx source code, I find this line: #define NGX_INT32_LEN sizeof(-2147483648) – 1

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When reading nginx source code, I find this line:

#define NGX_INT32_LEN   sizeof("-2147483648") - 1

why using sizeof(“-2147483648”) – 1?

not sizeof(-2147483648) – 1

not -2147483648 – 1

not -2147483649
or else?

What’s the difference?

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1 Answer

  1. Editorial Team

    Basically -2147483648 is the widest, in terms of characters required for its representation, of any of the signed 32-bit integers. This macro NGX_INT32_LEN defines how many characters long such an integer can be.

    It does this by taking the amount of space needed for that string constant, and subtracting 1 (because sizeof will provided space for the trailing NUL character). It’s quicker than using:

    strlen("-2147483648")

    because not all compilers will translate that into the constant 11.

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