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

Forwarding to -hackers.



----- Forwarded Message -----
> From: Kevin Grittner <kgrittn@ymail.com>
> To: Tom Lane <tgl@sss.pgh.pa.us>
> Cc: "pgsql-committers@postgresql.org" <pgsql-committers@postgresql.org>
> Sent: Friday, November 8, 2013 3:19 PM
> Subject: Re: [COMMITTERS] pgsql: Fix blatantly broken record_image_cmp() logic for pass-by-value
>
> Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
>>  That is a serious compiler bug which you should file with your
>>  distro forthwith.
>
> I distilled it down to the simplest case I could find which failed
> to produce the warning; attached. Do you agree that it is a
> compiler bug that this generates no warning?
>
> Compile lines used:
>
> gcc -O2 -Wall -Wmissing-prototypes -Wpointer-arith
> -Wdeclaration-after-statement -Wendif-labels
> -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
> -fwrapv -fexcess-precision=standard -g -D_GNU_SOURCE -c -o
> warning_test.o warning_test.c -MMD -MP
>
> clang -O2 -Wall -Wmissing-prototypes -Wpointer-arith
> -Wdeclaration-after-statement -Wendif-labels
> -Wmissing-format-attribute -Wformat-security -fno-strict-aliasing
> -fwrapv -g -D_GNU_SOURCE -c -o warning_test.o warning_test.c -MMD
> -MP
>
> It is probably significant that if I simplify the while loop
> condition to just use one variable I do get the warning.
>
>>  It definitely does show up with what I'm using:
>>          gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-3)
>
> The warning shows up, or the bug does?
>
>>  It might be worth trawling the buildfarm records to see which
>>  compilers did or didn't warn before.
>
> I'll get this filed first with the version I'm using, then look
> around to see if there is anything else to report.
>
>
> --
> Kevin Grittner
> EDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
>