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authorRoberto Ierusalimschy <roberto@inf.puc-rio.br>2014-12-27 18:32:26 -0200
committerRoberto Ierusalimschy <roberto@inf.puc-rio.br>2014-12-27 18:32:26 -0200
commit1a7868c1d55592a59f6ffa75ad1bd6330282b7fe (patch)
treedb7facd15907e6321e2a4909e6f26dbe09f6bc18 /lmathlib.c
parentde3933480e729577355b18c086d2e3c341c17aa6 (diff)
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bug: 'random' limit is 2^31-1, not RAND_MAX
Diffstat (limited to 'lmathlib.c')
-rw-r--r--lmathlib.c8
1 files changed, 5 insertions, 3 deletions
diff --git a/lmathlib.c b/lmathlib.c
index a643ef73..1925e826 100644
--- a/lmathlib.c
+++ b/lmathlib.c
@@ -1,5 +1,5 @@
1/* 1/*
2** $Id: lmathlib.c,v 1.112 2014/11/02 19:19:04 roberto Exp roberto $ 2** $Id: lmathlib.c,v 1.113 2014/11/07 11:31:58 roberto Exp roberto $
3** Standard mathematical library 3** Standard mathematical library
4** See Copyright Notice in lua.h 4** See Copyright Notice in lua.h
5*/ 5*/
@@ -27,9 +27,11 @@
27#if defined(LUA_USE_POSIX) 27#if defined(LUA_USE_POSIX)
28#define l_rand() random() 28#define l_rand() random()
29#define l_srand(x) srandom(x) 29#define l_srand(x) srandom(x)
30#define L_RANDMAX 2147483647 /* (2^31 - 1), following POSIX */
30#else 31#else
31#define l_rand() rand() 32#define l_rand() rand()
32#define l_srand(x) srand(x) 33#define l_srand(x) srand(x)
34#define L_RANDMAX RAND_MAX
33#endif 35#endif
34#endif /* } */ 36#endif /* } */
35 37
@@ -233,12 +235,12 @@ static int math_max (lua_State *L) {
233 235
234/* 236/*
235** This function uses 'double' (instead of 'lua_Number') to ensure that 237** This function uses 'double' (instead of 'lua_Number') to ensure that
236** all bits from 'l_rand' can be represented, and that 'RAND_MAX + 1.0' 238** all bits from 'l_rand' can be represented, and that 'RANDMAX + 1.0'
237** will keep full precision (ensuring that 'r' is always less than 1.0.) 239** will keep full precision (ensuring that 'r' is always less than 1.0.)
238*/ 240*/
239static int math_random (lua_State *L) { 241static int math_random (lua_State *L) {
240 lua_Integer low, up; 242 lua_Integer low, up;
241 double r = (double)l_rand() * (1.0 / ((double)RAND_MAX + 1.0)); 243 double r = (double)l_rand() * (1.0 / ((double)L_RANDMAX + 1.0));
242 switch (lua_gettop(L)) { /* check number of arguments */ 244 switch (lua_gettop(L)) { /* check number of arguments */
243 case 0: { /* no arguments */ 245 case 0: { /* no arguments */
244 lua_pushnumber(L, (lua_Number)r); /* Number between 0 and 1 */ 246 lua_pushnumber(L, (lua_Number)r); /* Number between 0 and 1 */