[1.1.42] Crash when getting debug info in bytecode with null local debug names
Posted: Tue Oct 19, 2021 6:26 pm
What
When Lua tries to get the debug synbol name / varname for a register it crashes if that register currently has a "local" name that is `NULL` (or 0 or nullptr, whichever you prefer).Expected
I'd expect Lua not to crash, and I believe it is because this function assumes that all varnames are not `NULL`.The proper fix for this would be to validate that the given bytecode does not contain null strings for local debug symbols, similar to how the constant table must not contain null strings.
However, there is an alternative fix which I personally would prefer:
Allow "unnamed" registers (meaning local debug symbols with `NULL` names) between the registers that represent the local variables.
This may be a bit of a deviation from regular Lua, but it would allow me - or rather phobos, the compiler I'm working on - to have some crazy register management since Lua technically does not enforce normal stack behavior for it's stack. Additinally it would allow naming temporary registers to better describe what value they are holding instead of "?". For example when calling `foo[bar]()` where `foo[bar]` evaluates to nil, Lua falls back to "Attempt to call '?' (a nil value)". Phobos, or any bytecode compiler, could provide a better name, such that the error would be "Attempt to call local '(foo[bar])' (a nil value)", but in the process must pad all registers up to that location in the stack with some "unnamed" local name.
Reproduce
Run this commandCode: Select all
/c
assert(load("\z
\027\z L\z u\z a\z R\000\001\004\008\004\008\000\025\147\013\010\026\010\000\000\000\000\000\000\000\000\000\001\002\005\000\000\z
\000\z %\000\000\000\z @\000\000\000\z ]\z @\128\000\031\000\128\000\031\000\128\000\001\000\000\000\004\z 1\000\000\000\000\000\z
\000\000\027\z P\z h\z o\016\z B\255\000\000\000\000\000\000\000\000\000\005\000\000\000\007\000\000\000\001\000\000\000\004\000\z
\000\000\001\000\000\000\001\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\002\000\000\000\004\000\000\000\000\z
\000\003\006\000\000\000\006\000\z @\000\007\z @\z @\000\z A\128\000\000\129\192\000\000\029\z @\128\001\031\000\128\000\005\000\z
\000\000\004\006\000\000\000\000\000\000\000\z d\z e\z b\z u\z g\000\004\008\000\000\000\000\000\000\000\z g\z e\z t\z i\z n\z f\z
\z o\000\003\000\000\000\000\000\000\240\z ?\004\002\000\000\000\000\000\000\000\z n\000\004\z 5\000\000\000\000\000\000\000\027\z
\z P\z h\z o\016\z B\255\000\007\000\000\000\001\000\000\000\006\000\000\000\003\000\000\000\008\000\000\000\017\000\000\000\020\z
\000\000\000\016\000\000\000\001\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\000\000\015\000\z
\000\000\000\000\000\000\z @\z t\z e\z m\z p\z /\z t\z e\z s\z t\z .\z l\z u\z a\000\006\000\000\000\003\000\000\000\003\000\000\z
\000\003\000\000\000\003\000\000\000\003\000\000\000\004\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000\000\000\000\z
\000\001\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\005\000\000\000\000\000\000\000\000\000\000\000\002\000\000\z
\000\005\000\000\000\000\000\000\000\000\000\000\000\003\000\000\000\005\000\000\000\001\000\000\000\005\000\000\000\000\000\000\z
\000\z _\z E\z N\z V\000\001\000\000\000\001\000\015\000\000\000\000\000\000\000\z @\z t\z e\z m\z p\z /\z t\z e\z s\z t\z .\z l\z
\z u\z a\000\005\000\000\000\002\000\000\000\006\000\000\000\006\000\000\000\008\000\000\000\008\000\000\000\002\000\000\000\000\z
\000\000\000\000\000\000\000\000\000\000\000\004\000\000\000\000\000\000\000\000\000\000\000\001\000\000\000\003\000\000\000\001\z
\000\000\000\005\000\000\000\000\000\000\000\z _\z E\z N\z V\000\z
", nil, 'b'))()
Code: Select all
local function foo()
debug.getinfo(1, "n")
end
foo()
return
