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Introduce spaceship comparison for Processes

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If currently two unsigned values are compared via `a - b`, in the case b
is actually bigger than a, the result will not be an negative number (as
-1 is expected) but a huge positive number as the subtraction is an
unsigned subtraction.

Avoid over-/underflow affected operations; use comparisons.
Modern compilers will generate sane code, like:
    xor     eax, eax
    cmp     rdi, rsi
    seta    al
    sbb     eax, 0
    ret
This commit is contained in:
Christian Göttsche
2020-11-04 17:46:24 +01:00
committed by BenBE
parent d785b1bbc3
commit 397b5c4bd0
7 changed files with 111 additions and 84 deletions
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16
Macros.h
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@ -4,19 +4,27 @@
#include <assert.h> // IWYU pragma: keep
#ifndef MINIMUM
#define MINIMUM(a, b) ((a) < (b) ? (a) : (b))
#define MINIMUM(a, b) ((a) < (b) ? (a) : (b))
#endif
#ifndef MAXIMUM
#define MAXIMUM(a, b) ((a) > (b) ? (a) : (b))
#define MAXIMUM(a, b) ((a) > (b) ? (a) : (b))
#endif
#ifndef CLAMP
#define CLAMP(x, low, high) (assert((low) <= (high)), ((x) > (high)) ? (high) : MAXIMUM(x, low))
#define CLAMP(x, low, high) (assert((low) <= (high)), ((x) > (high)) ? (high) : MAXIMUM(x, low))
#endif
#ifndef ARRAYSIZE
#define ARRAYSIZE(x) (sizeof(x) / sizeof((x)[0]))
#define ARRAYSIZE(x) (sizeof(x) / sizeof((x)[0]))
#endif
#ifndef SPACESHIP_NUMBER
#define SPACESHIP_NUMBER(a, b) (((a) > (b)) - ((a) < (b)))
#endif
#ifndef SPACESHIP_NULLSTR
#define SPACESHIP_NULLSTR(a, b) strcmp((a) ? (a) : "", (b) ? (b) : "")
#endif
#ifdef __GNUC__ // defined by GCC and Clang