ref: ce450582513dcea0d8f7b721ab693b954332f5ba
dir: /posix-386/tas.c/
#include "u.h" #include "libc.h" int tas(int *x) { int v; __asm__( "movl $1, %%eax\n\t" "xchgl %%eax,(%%ecx)" : "=a" (v) : "c" (x) ); switch(v) { case 0: case 1: return v; default: print("canlock: corrupted 0x%lux\n", v); return 1; } }