reducing patch complexity and conflicts
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- Subject: reducing patch complexity and conflicts
- From: David Manura <dm.lua@...>
- Date: 2010年11月26日 00:12:46 -0500
Some changes might be made in the Lua source to reduce the complexity
of patches and the likelihood of conflicts between patches.
Consider the "continue" patch [1], which extends the lexer like this:
-------------------------
const char *const luaX_tokens [] = {
- "and", "break", "do", "else", "elseif",
+ "and", "break", "continue", "do", "else", "elseif",
"end", "false", "for", "function", "if",
---
#define FIRST_RESERVED 257
---
enum RESERVED {
/* terminal symbols denoted by reserved words */
- TK_AND = FIRST_RESERVED, TK_BREAK,
+ TK_AND = FIRST_RESERVED, TK_BREAK, TK_CONTINUE,
TK_DO, TK_ELSE, TK_ELSEIF, TK_END, TK_FALSE, TK_FOR, TK_FUNCTION,
-------------------------
That will conflict with other patches that extend the lexer with
nearby keywords. I'd suggest the lexer being written like this:
----------------------------
static const char *const luaX_tokens [] = {
/* terminal symbols denoted by reserved words */
"and",
"break",
"do",
"else",
.....
---------------------------
enum RESERVED {
/* terminal symbols denoted by reserved words */
TK_RESERVED_BEFORE = FIRST_RESERVED - 1,
TK_AND,
TK_BREAK,
TK_DO,
.....
TK_WHILE,
TK_RESERVED_AFTER,
/* other terminal symbols */
TK_OTHER_BEFORE = TK_RESERVED_AFTER - 1,
TK_CONCAT
.....
/* number of reserved words */
#define NUM_RESERVED (cast(int, TK_RESERVED_AFTER - TK_RESERVED_BEFORE - 1))
---------------------------
Similar things might be done elsewhere, such as adding a placeholder
after VINDEXED in expkind to avoid the hardcoded comparison here,
which will break if another variable kind is added after VINDEXED:
#define vkisvar(k) (VLOCAL <= (k) && (k) <= VINDEXED)
One may also write a Lua script that validates constraints like
"ORDERED RESERVED" on patched Lua sources.
[1] http://lua-users.org/wiki/LuaPowerPatches