Limit maximum memory alloc with nice error info
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- Subject: Limit maximum memory alloc with nice error info
- From: bil til <biltil52@...>
- Date: Tue, 1 Nov 2022 11:53:38 +0100
Hi,
I want to be sure that any Lua user trying to alloc too large memory
objects would see immediately.
In my "restricted RAM (60kB Lua alloc memory only)" application, I
want to limit the maximum alloc size to 5kB.
So e. g. the command
str= string.rep( 'x', 6000)
should stop Lua with some "nice error info".
I use own alloc function.
My first try was, just to return zero, if size there is above 5000.
Then Lua stops with error "not enough memory" ... this is a bit not so
nice error, as line info missing (Lua alloc function does not contain
L, therefore I cannot invoike luaL_error(L, msg), as usually required
for this.
Looking at the call stack in this situation, the Lua function invoking
alloc is called
void *luaM_malloc_ (lua_State *L, size_t size, int tag) { ...} (in lmem.c)
This is fine, if I include there the 4 lines:
if( size > 5000){ //2022-11-01 //Wf
extern const char* cpctoolong;
luaL_error( L, cpctoolong);
}
Then my Lua user gets a nice error message "too long" with program
line info where this happens.
Is this a "reasonable way" to attack this task?
Or some more "generalized way" possible?
(I am a bit disturbed, that there is no "standard procedure" for such
a limit, I think to present a safe and clear Lua programming
experience to the user, this somehow should be limited in any program
... just on larger systems of course with much higher limit value
then?).