Re: [PATCH 2/4] cleanup: use internal memory allocation wrapper functions everywhere

> On Thu, Oct 6, 2011 at 6:14 PM, Brandon Casey <drafnel@gmail.com> wrote:
>> [removed Alexey Shumkin from cc]
>>
>> On Thu, Oct 6, 2011 at 1:17 AM, Johannes Sixt <j.sixt@viscovery.net> wrote:
>>> Am 10/6/2011 4:00, schrieb Brandon Casey:
>>>> [resend without html bits added by "gmail offline"]
>>>> On Wed, Oct 5, 2011 at 7:53 PM, Brandon Casey <drafnel@gmail.com> wrote:
>>>>> On Thursday, September 15, 2011, Brandon Casey wrote:
>>>>>>
>>>>>> On Thu, Sep 15, 2011 at 1:52 AM, Johannes Sixt <j.sixt@viscovery.net>
>>>>>>> There is a danger that the high-level die() routine (which is used by
>>>>>>> the
>>>>>>> x-wrappers) uses one of the low-level compat/ routines. IOW, in the case
>>>>>>> of errors, recursion might occur. Therefore, I would prefer that the
>>>>>>> compat/ routines do their own error reporting (preferably via return
>>>>>>> values and errno).
>>>>>>
>>>>>> Thanks.  Will do.
>>>>>
>>>>> Hi Johannes,
>>>>> I have taken a closer look at the possibility of recursion with respect to
>>>>> die() and the functions in compat/.  It appears the risk is only related to
>>>>> vsnprintf/snprintf at the moment.  So as long as we avoid calling xmalloc et
>>>>> al from within snprintf.c, I think we should be safe from recursion.
>>>>> I'm inclined to keep the additions to mingw.c and win32/syslog.c since they
>>>>> both already use the x-wrappers or strbuf, even though they could easily be
>>>>> worked around.  The other file that was touched is compat/qsort, which
>>>>> returns void and doesn't have a good alternative error handling path.  So,
>>>>> I'm inclined to keep that one too.
>>>
>>> I'm fine with keeping the change to mingw.c (getaddrinfo related) and
>>> qsort: both are unlikely to be called from die().
>>>
>>> But syslog() *is* called from die() in git-daemon, and it would be better
>>> to back out the other offenders instead of adding to them.
>>
>> Ah.  Yes, you're right.  x-wrappers should not be used in syslog.c and
>> the use of strbuf's should be replaced.
>
> Good point. The patch for this looks something like this:
>
> diff --git a/compat/win32/syslog.c b/compat/win32/syslog.c
> index 42b95a9..243538c 100644
> --- a/compat/win32/syslog.c
> +++ b/compat/win32/syslog.c
> @@ -1,5 +1,4 @@
>  #include "../../git-compat-util.h"
> -#include "../../strbuf.h"
>
>  static HANDLE ms_eventlog;
>
> @@ -16,13 +15,8 @@ void openlog(const char *ident, int logopt, int facility)
>
>  void syslog(int priority, const char *fmt, ...)
>  {
> -       struct strbuf sb = STRBUF_INIT;
> -       struct strbuf_expand_dict_entry dict[] = {
> -               {"1", "% 1"},
> -               {NULL, NULL}
> -       };
>        WORD logtype;
> -       char *str;
> +       char *str, *pos;
>        int str_len;
>        va_list ap;
>
> @@ -39,11 +33,20 @@ void syslog(int priority, const char *fmt, ...)
>        }
>
>        str = malloc(str_len + 1);
> +       if (!str)
> +               return; /* no chance to report error */
> +
>        va_start(ap, fmt);
>        vsnprintf(str, str_len + 1, fmt, ap);
>        va_end(ap);
> -       strbuf_expand(&sb, str, strbuf_expand_dict_cb, &dict);
> -       free(str);
> +
> +       while ((pos = strstr(str, "%1")) != NULL) {
> +               str = realloc(str, ++str_len + 1);
> +               if (!str)
> +                       return;
> +               memmove(pos + 2, pos + 1, strlen(pos));
> +               pos[1] = ' ';
> +       }