Use of math.huge on 64bit Linux
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- Subject: Use of math.huge on 64bit Linux
- From: Sean Conner <sean@...>
- Date: Wed, 5 Mar 2014 15:16:05 -0500
Okay, I'm using Lua 5.1.5 (and all the patches [1]) and for the life of
me, I can't figure out what I'm doing wrong. I have this script:
proc = require "org.conman.process" -- [2]
print(math.huge)
proc.limits.soft.core = math.huge
print(proc.limits.soft.core)
On 32-bit Linux, the output is as expected:
inf
inf
But on two different 64-bit Linux systems, I get:
inf
0
I'm not seeing any obvious issues with the function [3]. I traced into
the function, and after it executes:
ival = lua_tonumber(L,3);
ival is 0, when it should be HUGE_VAL (which on Linux, prints out as 'inf').
Tracing into lua_tonumber() doesn't reveal anything, so next, write a
simplified test program to hopefully isolate the issue:
#include <stdio.h>
#include <lua.h>
#include <lauxlib.h>
static int huge(lua_State *L)
{
lua_Number ival;
if (lua_isnumber(L,1))
ival = lua_tonumber(L,1);
else
return 0;
printf("%f\n",ival);
return 0;
}
int luaopen_huge(lua_State *L)
{
lua_pushcfunction(L,huge);
return 1;
}
And the following script:
huge = require "huge"
huge(math.huge)
huge(0)
Running this on both 64-bit systems, the output is:
inf
0
which is *NOT* what I expected (and is, in fact, correct). So obviously, I
haven't isolated the issue, but I'm not just seeing what could be going
wrong. I don't think it's because of the fact that I compiled everything
into a custom Lua interpreter with all the modules built in, because I built
in the above module and it still worked.
I'm missing something obvious and I'm not seeing it.
-spc (Aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaah!)
[1] http://www.lua.org/bugs.html#5.1.5
[2] https://github.com/spc476/lua-conmanorg/blob/master/src/process.c
[3] https://github.com/spc476/lua-conmanorg/blob/master/src/process.c#L1184