avoid overflows in computation of step size

1 files changed, 8 insertions, 1 deletions

diff --git a/llimits.h b/llimits.h
index 14940550..909aba3b 100644
--- a/llimits.h
+++ b/llimits.h
@@ -1,5 +1,5 @@
 /*
-** $Id: llimits.h,v 1.141 2015/11/19 19:16:22 roberto Exp roberto $
+** $Id: llimits.h,v 1.142 2017/04/24 18:06:12 roberto Exp roberto $
 ** Limits, basic types, and some other 'installation-dependent' definitions
 ** See Copyright Notice in lua.h
 */
@@ -52,6 +52,13 @@ typedef unsigned char lu_byte;
 
 
 /*
+** floor of the log2 of the maximum signed value for integral type 't'.
+** (That is, maximum 'n' such that '2^n' fits in the given signed type.)
+*/
+#define log2maxs(t)     (sizeof(t) * 8 - 2)
+
+
+/*
 ** conversion of pointer to unsigned integer:
 ** this is for hashing only; there is no problem if the integer
 ** cannot hold the whole pointer value