Horton

Thread

Commits

  1. Suppress uninitialized-variable warning.

  2. Reap the benefits of not having to avoid leaking PGresults.

  3. Create infrastructure to reliably prevent leakage of PGresults.

  1. Compilation error with buildtype = release

    Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> — 2025-07-29T12:43:55Z

    Hi Tom,
I am seeing following error only with buildtype = release

FAILED: contrib/postgres_fdw/postgres_fdw.so.p/postgres_fdw.c.o
cc -Icontrib/postgres_fdw/postgres_fdw.so.p -Isrc/include
-I../../coderoot/pg/src/include -Isrc/interfaces/libpq
-I../../coderoot/pg/src/interfaces/libpq -fdiagnostics-color=always
-D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Werror -O3
-fno-strict-aliasing -fwrapv -fexcess-precision=standard -D_GNU_SOURCE
-Wmissing-prototypes -Wpointer-arith -Werror=vla -Wendif-labels
-Wmissing-format-attribute -Wimplicit-fallthrough=3
-Wcast-function-type -Wshadow=compatible-local -Wformat-security
-Wdeclaration-after-statement -Wno-format-truncation
-Wno-stringop-truncation -fPIC -pthread -fvisibility=hidden -MD -MQ
contrib/postgres_fdw/postgres_fdw.so.p/postgres_fdw.c.o -MF
contrib/postgres_fdw/postgres_fdw.so.p/postgres_fdw.c.o.d -o
contrib/postgres_fdw/postgres_fdw.so.p/postgres_fdw.c.o -c
../../coderoot/pg/contrib/postgres_fdw/postgres_fdw.c
../../coderoot/pg/contrib/postgres_fdw/postgres_fdw.c: In function
‘postgresAcquireSampleRowsFunc’:
../../coderoot/pg/contrib/postgres_fdw/postgres_fdw.c:5287:28: error:
‘reltuples’ may be used uninitialized in this function
[-Werror=maybe-uninitialized]
5287 |                 *totalrows = reltuples;
      |                 ~~~~~~~~~~~^~~~~~~~~~~
cc1: all warnings being treated as errors

meson setup command is
meson setup /build/prod --prefix /build/prod --werror --buildtype=release

Looking at the function, reltuples is indeed initialized in all the
cases. All the relevant lines of the function are at least 3 years
old, but I have started seeing this error only after
80aa9848befc13c188d2775a859deaf172fdd3a2.

Reading the code, reltuples is getting initialized in all the cases
when it's used i.e when method != ANALYZE_SAMPLE_OFF. I can't figure
out why that commit would cause this error. If I `git checkout
7d8f5957792421ec3bb9d1b9b6ca25d689d974b7` and build, I do not see the
error.

Compiler version
$ gcc --version
gcc (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

If I make the change as per attached patch, it compiles without an
error. I don't claim that the patch is the right thing to do, but it
might provide a hint.

-- 
Best Wishes,
Ashutosh Bapat

  2. Re: Compilation error with buildtype = release

    Tom Lane <tgl@sss.pgh.pa.us> — 2025-07-29T13:06:40Z

    Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> writes:
> I am seeing following error only with buildtype = release

Interesting.  I noticed skink showing the same thing as a warning,
but no other BF animals have shown it (yet anyway).

> Looking at the function, reltuples is indeed initialized in all the
> cases. All the relevant lines of the function are at least 3 years
> old, but I have started seeing this error only after
> 80aa9848befc13c188d2775a859deaf172fdd3a2.

Yeah.  The variable is clearly initialized in all cases where it's
used, but a compiler doing sloppy flow analysis might complain.
I suspect the relevance of 80aa9848b is that when there was a PG_TRY
in the function, these compilers backed off and didn't try to do flow
analysis at all.

> If I make the change as per attached patch, it compiles without an
> error. I don't claim that the patch is the right thing to do, but it
> might provide a hint.

Usually my answer to this sort of thing is to provide an initializer
for the variable.  Will fix.

			regards, tom lane

  3. Re: Compilation error with buildtype = release

    Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> — 2025-07-30T04:32:24Z

    On Tue, Jul 29, 2025 at 6:36 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Ashutosh Bapat <ashutosh.bapat.oss@gmail.com> writes:
> > I am seeing following error only with buildtype = release
>
> Interesting.  I noticed skink showing the same thing as a warning,
> but no other BF animals have shown it (yet anyway).
>
> > Looking at the function, reltuples is indeed initialized in all the
> > cases. All the relevant lines of the function are at least 3 years
> > old, but I have started seeing this error only after
> > 80aa9848befc13c188d2775a859deaf172fdd3a2.
>
> Yeah.  The variable is clearly initialized in all cases where it's
> used, but a compiler doing sloppy flow analysis might complain.
> I suspect the relevance of 80aa9848b is that when there was a PG_TRY
> in the function, these compilers backed off and didn't try to do flow
> analysis at all.
>
> > If I make the change as per attached patch, it compiles without an
> > error. I don't claim that the patch is the right thing to do, but it
> > might provide a hint.
>
> Usually my answer to this sort of thing is to provide an initializer
> for the variable.  Will fix.

Thanks.

-- 
Best Wishes,
Ashutosh Bapat