Re: Bug in storing -0 constant

[Roberto Ierusalimschy <roberto@...>]

> I've found a small bug in Lua 5.1.3 (and probably older versions as
> well).  The numbers 0 and -0 are treated as identical when used as table
> keys.  That's OK, but it leads to a problem when both numbers appear as
> constants in the same function, because the compiler only puts the first
> one into the constant table in the bytecode.

This is a known issue:

  http://lua-users.org/lists/lua-l/2005-01/msg00114.html

Many thanks anyway.

Update: it is not hard to fix this behavior:

--- lcode.c     2008/04/02 16:16:06     2.35
+++ lcode.c     2008/04/06 13:31:38
@@ -696,7 +696,7 @@
   e2.t = e2.f = NO_JUMP; e2.k = VKNUM; e2.u.nval = 0;
   switch (op) {
     case OPR_MINUS: {
-      if (isnumeral(e))  /* -constant? */
+      if (isnumeral(e) && e->u.nval != 0)  /* minus non-zero constant? */
         e->u.nval = luai_numunm(NULL, e->u.nval);
       else {
         luaK_exp2anyreg(fs, e);


-- Roberto