Concat strings using '+' crashes Love on my Mac

[patrickjcollins]

Hi chaps,

If I try to concat two strings with the '+' plus operator Love crashes on my MacBook. I've since learnt that concatenations are done with the ".." operator. RTFM and all that. Anyway, thus far Love has been presenting me clear and precise error messages, this crash was a bit of a surprise and took some hunting to figure out. Has anyone experienced the same thing?

Patrick

[zac352]

That's because you're calling the __add metamethod, which is nil.

Adding

Code: Select all

getmetatable("").__add=function(s1,s2) return s1..s2 end

before your code will fix it.

[patrickjcollins]

Wow, that was a fast reply. But is it normal that Love should crash without showing an error message? I have another crash going on at the moment, although it's not due to string concatenation, must be something else. So it's block comments and debug messages again...

[zac352]

Wow, that was a fast reply. But is it normal that Love should crash without showing an error message? I have another crash going on at the moment, although it's not due to string concatenation, must be something else. So it's block comments and debug messages again...

I saw your post after I logged in.

Uh... I've gotten crashes from the physics library. I think it may be some sort of bug in Love. Someone should probably look into that...

[cue post with link to bug]

[bartbes]

It's not a bug, it's a missing feature!

[zac352]

It's not a bug, it's a missing feature!

Lol.

[bmelts]

Whoa whoa whoa whoa whoa. Hang on.

First off, zac352: No. You're wrong. I just actually tried this myself, with the following code:

Code: Select all

function love.draw()
        love.graphics.print("hi "+"world", 400, 300)
end

And got the following:

main.lua:2: attempt to perform arithmetic on a string value

So. Attempting to use + errors properly. The crash, then is due to something else.

Here's a thought. Are you:
a) using LÖVE 0.6.2 (or older)
b) setting some variable named "debug" somewhere in your code

If both of those are true, that would explain the mysterious crashing - debug is a built-in Lua table, and LÖVE uses it to display the error screen; thus, trying to use it as a variable of your own means LÖVE can't call the debug code it needs, and thus the game just crashes. (For the record, this is fixed in the 0.7.0 beta.)

If the above is not the case... post your code, it'd make it a lot easier to debug.

[zac352]

Whoa whoa whoa whoa whoa. Hang on.

First off, zac352: No. You're wrong. I just actually tried this myself, with the following code:

Code: Select all

function love.draw()
        love.graphics.print("hi "+"world", 400, 300)
end

And got the following:

main.lua:2: attempt to perform arithmetic on a string value

So. Attempting to use + errors properly. The crash, then is due to something else.

Here's a thought. Are you:
a) using LÖVE 0.6.2 (or older)
b) setting some variable named "debug" somewhere in your code

If both of those are true, that would explain the mysterious crashing - debug is a built-in Lua table, and LÖVE uses it to display the error screen; thus, trying to use it as a variable of your own means LÖVE can't call the debug code it needs, and thus the game just crashes. (For the record, this is fixed in the 0.7.0 beta.)

If the above is not the case... post your code, it'd make it a lot easier to debug.

Last time I checked, setting a metamethod in any string sets that metamethod for all strings... Wait, it does. So, either you messed up, or we just found another missing feature.

Edit:
Put this code in the online Lua demo:

Code: Select all

getmetatable("").__add=function(s1,s2) return s1..s2 end

print("Hello"+" "+"World")

Which is here, if you fail to find it.

[bartbes]

It works, but it's still crap. Now get back on topic.

EDIT: To clarify, that is not making lua do concat with +, but rather the (lack of) errors.

[zac352]

It works, but it's still crap. Now get back on topic.

EDIT: To clarify, that is not making lua do concat with +, but rather the (lack of) errors.

While, what ever happened to the unusual microsoft C++ runtime library errors I get when I call love.physics.newWorld?