Обсуждение: Fw: [COMMITTERS] pgsql: Fix blatantly broken record_image_cmp() logic for pass-by-value

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----- Forwarded Message -----
> From: Kevin Grittner <kgrittn@ymail.com>
> To: Kevin Grittner <kgrittn@ymail.com>; Tom Lane <tgl@sss.pgh.pa.us>
> Cc: "pgsql-committers@postgresql.org" <pgsql-committers@postgresql.org>
> Sent: Friday, November 8, 2013 4:33 PM
> Subject: Re: [COMMITTERS] pgsql: Fix blatantly broken record_image_cmp() logic for pass-by-value
>
> Kevin Grittner <kgrittn@ymail.com> wrote:
>
>>  I distilled it down to the simplest case I could find which
>>  failed to produce the warning; attached.
>
> For a compiler which seems to like to generate warnings for really
> esoteric cases, clang falls down rather badly on uninitialized
> variables -- at least on the package for Ubuntu 12.10.  It does not
> complain at all about this:
>
>
> int warning_test(int a);
> int warning_test(int a)
> {
>     int result;
>
>     if (a == 1)
>         result = 1;
>
>     return result;
> }
>
>
> I assume that everyone here agrees that merits a warning?
>
> Bug reports filed.
>
>
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>

Kevin Grittner <kgrittn@ymail.com> wrote:

>>  int warning_test(int a);
>>  int warning_test(int a)
>>  {
>>      int result;
>>
>>      if (a == 1)
>>          result = 1;
>>
>>      return result;
>>  }

I had to file separate bug reports for gcc and clang.  I have
already gotten a response on the clang bug report using the above
test code.  It was closed with this response:

Fixed from clang 3.3
warning_test.c:8:6: warning: variable 'result' is used uninitialized whenever 'if' condition is
      false [-Wsometimes-uninitialized]
        if (a == 1)
            ^~~~~~
warning_test.c:11:9: note: uninitialized use occurs here
        return result;
              ^~~~~~
warning_test.c:8:2: note: remove the 'if' if its condition is always true
        if (a == 1)
        ^~~~~~~~~~~
warning_test.c:6:14: note: initialize the variable 'result' to silence this warning
        int                    result;
                                      ^
                                      = 0


** Changed in: clang (Ubuntu)
      Status: New => Fix Released


I take that to say that the bug will be fixed in clang version 3.3,
which is not available in any production release of Ubuntu.

--
Kevin Grittner
EDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company