diff options
| author | Mike Pall <mike> | 2022-12-22 00:03:06 +0100 |
|---|---|---|
| committer | Mike Pall <mike> | 2022-12-22 00:03:06 +0100 |
| commit | 8a5e398c52c7f8ca3e1a0e574cc2ba38224b759b (patch) | |
| tree | dae089564f58db2963bae8e3530c1faae104cc61 /src/lj_vmmath.c | |
| parent | b2791179ef96d652d00d78d2a8780af690537f6a (diff) | |
| download | luajit2-8a5e398c52c7f8ca3e1a0e574cc2ba38224b759b.tar.gz | |
Avoid negation of signed integers in C that may hold INT*_MIN.
Reported by minoki.
Recent C compilers 'take advantage' of the undefined behavior.
This completely changes the meaning of expressions like (k == -k).
Diffstat (limited to 'src/lj_vmmath.c')
| -rw-r--r-- | src/lj_vmmath.c | 8 |
1 files changed, 4 insertions, 4 deletions
diff --git a/src/lj_vmmath.c b/src/lj_vmmath.c index ff41ba28..6369bc6b 100644 --- a/src/lj_vmmath.c +++ b/src/lj_vmmath.c @@ -66,11 +66,11 @@ int32_t LJ_FASTCALL lj_vm_modi(int32_t a, int32_t b) { uint32_t y, ua, ub; lua_assert(b != 0); /* This must be checked before using this function. */ - ua = a < 0 ? (uint32_t)-a : (uint32_t)a; - ub = b < 0 ? (uint32_t)-b : (uint32_t)b; + ua = a < 0 ? ~(uint32_t)a+1u : (uint32_t)a; + ub = b < 0 ? ~(uint32_t)b+1u : (uint32_t)b; y = ua % ub; if (y != 0 && (a^b) < 0) y = y - ub; - if (((int32_t)y^b) < 0) y = (uint32_t)-(int32_t)y; + if (((int32_t)y^b) < 0) y = ~y+1u; return (int32_t)y; } #endif @@ -105,7 +105,7 @@ double lj_vm_powi(double x, int32_t k) else if (k == 0) return 1.0; else - return 1.0 / lj_vm_powui(x, (uint32_t)-k); + return 1.0 / lj_vm_powui(x, ~(uint32_t)k+1u); } /* Computes fpm(x) for extended math functions. */ |