Cleanup max upvalues constant a bit, add some luaconf.h assumptions

Author: kyren

Cargo.toml

@@ -21,6 +21,7 @@ default = ["builtin-lua"]
 #   * LUA_INTEGER is long long
 #   * LUA_NUMBER as double
 #   * LUA_EXTRASPACE is sizeof(void*)
+#   * LUAI_MAXSTACK is 1000000
 builtin-lua = ["gcc"]
 
 [dependencies]

src/ffi.rs

@@ -34,6 +34,8 @@ pub const LUAI_MAXSTACK: c_int = 1_000_000;
 pub const LUA_REGISTRYINDEX: c_int = -LUAI_MAXSTACK - 1000;
 pub const LUA_RIDX_MAINTHREAD: lua_Integer = 1;
 pub const LUA_RIDX_GLOBALS: lua_Integer = 2;
+// Not actually defined in lua.h / luaconf.h
+pub const LUA_MAX_UPVALUES: c_int = 255;
 
 pub const LUA_TNONE: c_int = -1;
 pub const LUA_TNIL: c_int = 0;

src/function.rs

@@ -146,12 +146,10 @@ impl<'lua> Function<'lua> {
         let lua = self.0.lua;
         unsafe {
             stack_err_guard(lua.state, 0, || {
-                const MAX_LUA_UPVALUES: c_int = 255;
-
                 let args = args.to_lua_multi(lua)?;
                 let nargs = args.len() as c_int;
 
-                if nargs + 2 > MAX_LUA_UPVALUES {
+                if nargs + 2 > ffi::LUA_MAX_UPVALUES {
                     return Err(Error::BindError);
                 }