Backporting to Lua 5.1

[ggcrunchy]

Hi.

I'm attempting what's described in the title. :)

I still have a few 5.3-specific functions to shim, but nothing that sounds too awful.

Am now trying to deal with the integers.

From what I can see, I can find all of the entity usage with luaL_checkinteger() and lua_pushinteger(), and then there are the opcodes in meta.c. Anything else to be aware of? (In flecs proper I suppose there might be the DSLs to consider.)

It looks like there's an integer vs. number case in the serialization logic, so a lua_Number (as suggested by this comment) won't be quite enough, but I'm thinking a light userdata would work on 64-bit targets, and maybe some hybrid number / full userdata approach otherwise, with some helper functions around them.

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(Maybe later I could adopt the LNUM patch, but not for the time being.)

[randy408]

I guess you could replace all the luaL_checkinteger() and lua_pushinteger()'s for entities with checkentity() and pushentity() and do compile-time checking for Lua <5.3.

The tests will probably not pass because there's a lot of checks for non-zero entity id's, maybe you could get away with returning lightuserdata for non-zero id's and nil / 0 otherwise. You have to consider what would work best in actual Lua code.

The occasional arithmetic on >32bit integers is probably a no-go and is why I never bothered with older Lua versions, 5.2 has been EOL since 2015, even 5.3 is EOL at this point.