Re: [PATCH v4 02/15] mingw: implement syslog

From: Erik Faye-Lund <kusmabite@gmail.com>
Date: Oct 13, 2010, 12:36 UTC
Message-ID: <AANLkTinBvZ_L-fq1u4tPX6rNW6X3jeoOO23-yLpdxSu0@mail.gmail.com>
In-Reply-To: <20101011223746.GA6637@burratino>

On Tue, Oct 12, 2010 at 12:37 AM, Jonathan Nieder <jrnieder@gmail.com> wrote:

Show 10 quoted lines

> Erik Faye-Lund wrote:
>
>> The string gets inlined into itself (with a limit of 100 expansions)
>> leading to string like "foo %1 bar" becoming "foo foo foo ... foo %1
>> bar bar bar ... bar". With our expansion, it becomes "foo % 1 bar"
>> instead.
>
> Ah, ok.  Sounds like there is no need to worry about requests for "%%1"
> etc.  Thanks for explaining.
>

Actually, %%1 is a bit of a tricky one. It seems that %%1 is used to escape %1 on Windows 7, but not on earlier Windows version. I did test this on Vista an XP earlier, but I'll re-test again later and report back, in case my earlier tests were flawed.

Can %%1 occur in an IPv6 address at all? If not, I'm tempted to not handle it (unless it turns out I was wrong about %%1-escaping on Vista and XP).

> Maybe the symptoms and cases not covered (%2, %%1) would be worth
> mentioning in the log message?
>

Sorry for the late reply.

I'm sure it could be added, I'm just a bit worried about making the whole commit message too intimidating.

Something like this, perhaps?

---8<--- Strings containing "%1" gets expanded into themselves by ReportEvent, so let's expand "%1" to "% 1" before reporting, because such string can occur in IPv6-addresses. "%2" and above does not appear to be a problem, probably because ReportEvent checks the number against the wNumStrings parameter first. "%%1" is still a problem, but we don't have a code-path producing such strings. ---8<---

This is (of course), assuming my current findings are correct.

The lack of documentation on the subject is really annoying.