Why is LuaJIT producing "too many callback errors" from this simple code?
I am using LuaJIT and throwing an "too many callbacks" exception with this code. I know there is a limit to the number of c callbacks that can be generated, but as far as I know this should just generate one callback ... right?
ffi = require('ffi')
ffi.cdef([[typedef double cpFloat;
typedef struct cpSpace cpSpace;
typedef struct cpBody cpBody;
cpSpace* cpSpaceNew(void);
cpBody* cpBodyNew(cpFloat mass, cpFloat moment);
cpBody* cpSpaceAddBody(cpSpace *space, cpBody *body);
typedef void (*cpSpaceBodyIteratorFunc)(cpBody *body, void *data);
void cpSpaceEachBody(cpSpace *space, cpSpaceBodyIteratorFunc func, void *data);
]])
chipmunk = ffi.load("chipmunk")
space = chipmunk.cpSpaceNew()
body = chipmunk.cpBodyNew(10, 100)
chipmunk.cpSpaceAddBody(space, body)
drawBody = function(body, x) end
CALL_COUNT = 5000
for i = 1, CALL_COUNT do
chipmunk.cpSpaceEachBody(space, drawBody, nil)
end
If CALL_COUNT is reduced to 500, it works without error.
The exception looks like this:
Error: main.lua:25: too many callbacks
stack traceback:
[C]: in function 'cpSpaceEachBody'
mainmoon.lua:25: in main chunk
[C]: in function 'require'
main.lua:1: in main chunk
[C]: in function 'require'
[string "boot.lua"]:374: in function <[string "boot.lua"]:244>
[C]: in function 'xpcall'
Context: I am integrating Chipmunk with the Love2D platform on Mac OS X.
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In LuaJIT, C callbacks are a finite resource. See http://luajit.org/ext_ffi_semantics.html#callback
Your function cpSpaceEachBody
takes a function as the second parameter. Every time you call it; you create a new function C.
In addition to making too many of them; you never free them.
You should use as few C functions as possible. In your example, you are using the same function every time, so this is a simple fix:
ffi = require('ffi')
ffi.cdef([[typedef double cpFloat;
typedef struct cpSpace cpSpace;
typedef struct cpBody cpBody;
cpSpace* cpSpaceNew(void);
cpBody* cpBodyNew(cpFloat mass, cpFloat moment);
cpBody* cpSpaceAddBody(cpSpace *space, cpBody *body);
typedef void (*cpSpaceBodyIteratorFunc)(cpBody *body, void *data);
void cpSpaceEachBody(cpSpace *space, cpSpaceBodyIteratorFunc func, void *data);
]])
chipmunk = ffi.load("chipmunk")
space = chipmunk.cpSpaceNew()
body = chipmunk.cpBodyNew(10, 100)
chipmunk.cpSpaceAddBody(space, body)
drawBody = function(body, x) end
drawBody_C_func = ffi.cast("cpSpaceBodyIteratorFunc", drawBody)
CALL_COUNT = 5000
for i = 1, CALL_COUNT do
chipmunk.cpSpaceEachBody(space, drawBody_C_func, nil)
end
drawBody_C_func:free()
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