青木日記

■ Bison 2.0 の罠 (1)

[ruby-core:6083]

うげ、パーサスタックを alloca しなくなったのか。 それはまずい……。

(13:20)

■ Bison 2.0 の罠 (2)

これかー

2004-12-22  Paul Eggert  <eggert@cs.ucla.edu>
　
        * NEWS: Bison-generated parsers no longer default to using the
        alloca function (when available) to extend the parser stack, due
        to widespread problems in unchecked stack-overflow detection.

うーむ、パース後に GC を起動するのはできるだけ避けたいしなあ。 パーサスタックを Ruby から取る方法があれば一番いいんだよな。 調べてみよう。

(13:27)

■ Bison 2.0 の罠 (3)

> Macro: YYSTACK_USE_ALLOCA
>
> Macro used to control the use of alloca when the C LALR(1) parser needs to
> extend its stacks. If defined to 0, the parser will use malloc to extend
> its stacks. If defined to 1, the parser will use alloca. Values other than
> 0 and 1 are reserved for future Bison extensions. If not defined,
> YYSTACK_USE_ALLOCA defaults to 0.
>
> If you define YYSTACK_USE_ALLOCA to 1, it is your responsibility to make
> sure that alloca is visible, e.g., by using GCC or by including <stdlib.h>.
> Furthermore, in the all-too-common case where your code may run on a host
> with a limited stack and with unreliable stack-overflow checking, you
> should set YYMAXDEPTH to a value that cannot possibly result in unchecked
> stack overflow on any of your target hosts when alloca is called. You can
> inspect the code that Bison generates in order to determine the proper
> numeric values. This will require some expertise in low-level
> implementation details.

と、いうことらしいですよ。うーむ。

うわあ、パーサスケルトンが m4 になってる。 きみらどうしてそんなに m4 が好きなんだ。

(14:01)

■ Bison 2.0 の罠 (4)

[ruby-list:41204]

早っ！

(15:36)