[9fans] email header screwup (and fix)

[9fans] email header screwup (and fix)

[erik quanstrom]

lately, i've been seeing email with gigantic headers.
120 header lines are not that uncommon.  unfortunately
upas has sometimes inserts a blank line about
(but not exactly) 4k into the file.  a bit of digging, upas/send
was assuming that if yacc didn't stop at a blank line, one should
be inserted. unfortunately, yacc was stopping because it ran out of stack
space.  the hack is to increase YYMAXDEPTH.  ideally,
each line should be parsed independently, thus making
yacc's depth depend only on the complexity of a line.

nupas on sources has the fix.

- erik

Re: [9fans] email header screwup (and fix)

[Russ Cox]

On Thu, Sep 9, 2010 at 4:13 PM, erik quanstrom <quanstro@quanstro.net> wrote:
> lately, i've been seeing email with gigantic headers.
> 120 header lines are not that uncommon.  unfortunately
> upas has sometimes inserts a blank line about
> (but not exactly) 4k into the file.  a bit of digging, upas/send
> was assuming that if yacc didn't stop at a blank line, one should
> be inserted. unfortunately, yacc was stopping because it ran out of stack
> space.  the hack is to increase YYMAXDEPTH.  ideally,
> each line should be parsed independently, thus making
> yacc's depth depend only on the complexity of a line.

or change the grammar not to need unlimited stack space.
it says

fields		: '\n'
			{ yydone = 1; }
		| field '\n'
		| field '\n' fields
		;

but i think you can change it to

fields	: fieldlist '\n'
			{ yydone = 1; }
		;

fieldlist	:
		| fieldlist field '\n'
		;

russ

Re: [9fans] email header screwup (and fix)

[erik quanstrom]

> or change the grammar not to need unlimited stack space.
> it says

yes.  you're right.  i should have fixed this properly
before posting.

> fields		: '\n'
> 			{ yydone = 1; }
> 		| field '\n'
> 		| field '\n' fields
> 		;
>
> but i think you can change it to
>
> fields	: fieldlist '\n'
> 			{ yydone = 1; }
> 		;
>
> fieldlist	:
> 		| fieldlist field '\n'
> 		;

i actually used this to avoid shift/reduce conflict
warnings

msg		: fields
		| unixfrom '\n' fields
		;
fields		: fieldlist '\n'
			{ yydone = 1; }
		;
fieldlist		: field '\n'
		| fieldlist field '\n'
		;

- erik