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From Rainer Jung <rainer.j...@kippdata.de>
Subject Re: [users@httpd] HTTPD 2.4.25 crash in mod_proxy (ajp)
Date Thu, 22 Dec 2016 23:11:20 GMT
Am 22.12.2016 um 23:56 schrieb Yann Ylavic:
> On Thu, Dec 22, 2016 at 11:38 PM, Rainer Jung <rainer.jung@kippdata.de> wrote:
>> OK, looking closer at the suggested patch I see it fixes trace2-Loggging.
>> When I activate e.g. trace8, I do get the expected crash in
>> ap_proxy_check_connection.
>
> Yes, it depends on the LogLevel, and probably also on AP_HAVE_C99
> (which avoids ap_log_* args evaluation when the LogLevel doesn't
> match).

Ah yes, you are right.

> How is AP_HAVE_C99 defined with msvc (or the compiler used at apachelounge)?
> If undefined/zero, it may segfault at any level.

It seems we set AP_HAVE_C99 in include/ap_config.h depending on 
__STDC_VERSION__. Various sources suggest MSVC isn't setting 
__STDC_VERSION__:

https://connect.microsoft.com/VisualStudio/feedback/details/1006806/c99-support-is-missing-stdc-version

So it could well be, that Windows users run into this with any log level.

@Jim: it only happens when backend connections get reused (that's what 
the broken log statement is logging), so e.g. not on the first request.

>> @Yann: your patch is just to check whether that is the problem? I guess the
>> final patch will distinguish between conn->connection being NULL (then using
>> your suggested code) or non-NULL (then using the original code). Or would
>> you always use your suggested code?
>
> I was thinking about always using the new code, maybe with an "if
> APLOGtrace2(s)" around to save a getsockname() call when not needed.

I see, thanks.

Regards,

Rainer

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