On Sun, Oct 10, 2010 at 11:28 PM, Eric Sunshine <ericsunshine@xxxxxxxxx> wrote:
> On 10/10/2010 4:37 PM, Erik Faye-Lund wrote:
>>
>> On Sun, Oct 10, 2010 at 9:50 PM, Eric Sunshine<ericsunshine@xxxxxxxxx>
>> wrote:
>>>
>>> On 10/10/2010 9:20 AM, Erik Faye-Lund wrote:
>>>>
>>>> From: Mike Pape<dotzenlabs@xxxxxxxxx>
>>>>
>>>> Syslog does not usually exist on Windows, so we implement our own
>>>> using Window's ReportEvent mechanism.
>>>>
>>>> Signed-off-by: Mike Pape<dotzenlabs@xxxxxxxxx>
>>>> Signed-off-by: Erik Faye-Lund<kusmabite@xxxxxxxxx>
>>>> ---
>>>> +void syslog(int priority, const char *fmt, const char *arg)
>>>> +{
>>>> + WORD logtype;
>>>> +
>>>> + if (!ms_eventlog)
>>>> + return;
>>>> +
>>>> + if (strcmp(fmt, "%s")) {
>>>> + warning("format string of syslog() not implemented");
>>>> + return;
>>>> + }
>>>
>>> It is not exactly clear what the intention is here. Is this trying to say
>>> that no formatting directives are allowed in 'fmt' or what? The simple
>>> case
>>> it is actually checking (where 'fmt' is solely '%s') could easily be
>>> handled
>>> manually, as could more complex formats.
>>>
>>
>> This is the result of the feed-back in v1, where we tried to implement
>> all format strings.
>
> In retrospect, when thinking more carefully about the conditional
> expression, I suppose the code is self-documenting, though perhaps a comment
> in code or in commit message would help.
>
>> But that turned out to be very complex (due to the
>> lack of a portable va_copy()) and since we control all call-sites for
>> syslog and already only use "%s" as the format, it should be OK.
>
> Do you mean vsnprintf() rather than va_copy()?
>
OK, I had to read some old discussions to figure out what the issue was :)
The problem was lack of portable va_copy, because I tried to add a
non-variadic version of strbuf_addf(), namely strbuf_vaddf() to do the
work.
I guess it could be implemented pretty easily with vsnprintf(),
though. I was afraid of doing that originally because I know there's
portability issues with the return value of snprintf. Luckily it seems
that we have a fix for that in compat/sprintf.c, and we rely on the
return value being correct in strbuf_addf() so it would probably be
safe.
Something like this (on top)
---8<---
diff --git a/compat/mingw.c b/compat/mingw.c
index bbe45d0..e3f3f92 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -1435,17 +1435,24 @@ void openlog(const char *ident, int logopt,
int facility)
warning("RegisterEventSource() failed: %lu", GetLastError());
}
-void syslog(int priority, const char *fmt, const char *arg)
+void syslog(int priority, const char *fmt, ...)
{
WORD logtype;
+ char *str;
+ int str_len;
+ va_list ap;
if (!ms_eventlog)
return;
- if (strcmp(fmt, "%s")) {
- warning("format string of syslog() not implemented");
- return;
- }
+ va_start(ap, fmt);
+ str_len = vsnprintf(NULL, 0, fmt, ap);
+ va_end(ap);
+
+ str = malloc(str_len + 1);
+ va_start(ap, fmt);
+ vsnprintf(str, str_len, fmt, ap);
+ va_end(ap);
switch (priority) {
case LOG_EMERG:
@@ -1478,8 +1485,9 @@ void syslog(int priority, const char *fmt, const
char *arg)
NULL,
1,
0,
- (const char **)&arg,
+ (const char **)&str,
NULL);
+ free(str);
}
#undef signal
diff --git a/compat/mingw.h b/compat/mingw.h
index aed49d8..45a63a0 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -186,7 +186,7 @@ int setitimer(int type, struct itimerval *in,
struct itimerval *out);
int sigaction(int sig, struct sigaction *in, struct sigaction *out);
int link(const char *oldpath, const char *newpath);
void openlog(const char *ident, int logopt, int facility);
-void syslog(int priority, const char *fmt, const char *arg);
+void syslog(int priority, const char *fmt, ...);
/*
* replacements of existing functions
---8<---
>> Are you suggesting that we report an error when we can't report the
>> string correctly? We could do that, but I'm not sure how the end-user
>> would benefit from that. ReportEvent is used to report errors (unless
>> the --verbose flag has been specified), and reporting that we can't
>> present an error message strike me as a bit confusing... Even the
>> corrupted error message is probably better :P
>
> I am not suggesting reporting an error. As a first-time reader of the code,
> I was trying to understand the presence of the comment which did not really
> seem to relate to the code. Perhaps adding a "FIXME" to the comment saying
> that the condition should perhaps be handled in the future would help to
> explain the comments presence.
>
A FIXME would certainly a good idea, if I don't just end up supporting
varargs here.
> (On the other hand, for the '%s' check above, the code does report a warning
> and then exits, so it is not inconceivable that a '%n' could also emit a
> warning.)
>
I guess I could add something like this:
if (strstr(arg, "%1"))
warning("arg contains %1, message might be corrupted");
I don't want to return in that case, because I think some output is
better than no output, and it seems to work on Vista. In fact, working
on Vista is kind of demotivating me to add such a warning in the first
place...
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