How to crash the Lua compiler with one line

[HyperHacker]

I implemented Lua into my app and discovered that the use of big numbers will cause an FPU exception when the program is run or even compiled, depending how they're used. The exception is the same every time:

Exception - FPU Exception (V)
Thread ID - 0x0435861B
Th Name   - user_main
Module ID - 0x0437DD0F
Mod Name  - shell
EPC       - 0x0881FB8C
Cause     - 0x1000003C
BadVAddr  - 0x04405470
Status    - 0x20088613
zr:0x00000000 at:0x08870000 v0:0x00000003 v1:0x00000003
a0:0x0887C070 a1:0x0BBBEF08 a2:0x0887C070 a3:0x00000001
t0:0x00000005 t1:0xFFFFFFFF t2:0x08867090 t3:0xFFFFFFFC
t4:0x088670C8 t5:0xFFFFFFF8 t6:0x00000000 t7:0xDEADBEEF
s0:0x0887C070 s1:0x0BBBEF08 s2:0x08875BD0 s3:0x0BBBEF08
s4:0x08875BD0 s5:0x0BBBF2A8 s6:0x0BBBEF78 s7:0x0000000C
t8:0xDEADBEEF t9:0xDEADBEEF k0:0x0BBBFF00 k1:0x00000000
gp:0x0886F750 sp:0x0BBBEEC8 fp:0x00000000 ra:0x0881FC00
0x0881FB8C: 0x4600100D '...F' - trunc.w.s  $fpr00, $fpr02

Having any numeric constant greater than 0x7FFFFFBF (as hex or decimal) in the script will cause luaL_loadfile() to throw this exception. E.g.:

function FrameBegin()
	print(tostring(0x7FFFFFFF))
end

function FrameBegin()
	print(tostring(0x7FFFFF00 + 0xC0))
end

Either of these scripts will do it. You don't even have to run them, just loading them into memory is enough.

Adding at runtime has interesting side effects. If I do this (where foo() is a C function):

x = 1
function FrameBegin()
	foo(0x7FFFFF00 + x)
	x = x + 1
end

Then it will run as normal until x becomes 0xC0, and then crash. If I don't attempt to pass it to a C function, something else happens:

x = 1
function FrameBegin()
	print("X = ", string.format("%X", (0x7FFFFF00 + x)))
	x = x + 1
end

The program won't crash, but the addition will be wrong; x is rounded down to the closest multiple of 0x80. (i.e. until x reaches 0x80, the result of this addition will be 0x7FFFFF00, and then until it reaches 0x100, the result will be 0x7FFFFF80.)

I suspect the addition problem is simply floating point precision loss, but when merely having these constants in your script crashes Lua before it's even executed, that's a bigger problem. :-/