exponent and modulus operator oddities on ppc

[Glenn McAllister <glenn@...>]

We've been having some odd problems with the exponent operator ('^') and 
modulus operator ('%') on our PowerPC deployment environment; this issue 
doesn't exist on our x86 development environment.  We cross compile on 
x86 to the ppc target.

The tombstone data is:

Lua: 5.1.3

Make:
  make -C src MYCFLAGS="-DLUA_USE_POSIX -DLUA_USE_DLOPEN" 
MYLIBS="-Wl,-E -ldl -lncurses" all

Make Output:

powerpc-linux-gcc -O2 -Wall -DLUA_USE_POSIX -DLUA_USE_DLOPEN   -c -o 
lapi.o lapi.c
powerpc-linux-gcc -O2 -Wall -DLUA_USE_POSIX -DLUA_USE_DLOPEN   -c -o 
lcode.o lcode.c
powerpc-linux-gcc -O2 -Wall -DLUA_USE_POSIX -DLUA_USE_DLOPEN   -c -o 
ldebug.o ldebug.c

<snip/>

Host: ppc 32-bit

Given the following script, it produces the correct results on both x86 
and ppc:

 y = 2^3
 print('y = ', y)

 x = 10 % y
 print('x = ', x)

 y = 2^3
 print('y = ', y)

The output on both platforms is:

 y =     8
 x =     2
 y =     8

However, if we run the morally equivalent series of operations directly 
in the lua interpreter on the target ppc system, we get a different result:

 Lua 5.1.3  Copyright (C) 1994-2008 Lua.org, PUC-Rio
 > x = 2^3
 > =x
 8
 > y = 10 % x
 > =y
 2
 > z = 2^3
 > =z
 4.0096609170284

We've seen similar oddities in other lua apps we've written in the past. 
 This just happens to be the smallest subset of statements that seems 
to reproduce the problem consistently.

--
Glenn McAllister     <glenn@somanetworks.com>      +1 416 348 1594
SOMA Networks, Inc.  http://www.somanetworks.com/  +1 416 977 1414