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Re: Silence -Wmaybe-uninitialized warnings - Mailing list pgsql-hackers

From Imran Zaheer
Subject Re: Silence -Wmaybe-uninitialized warnings
Date
Msg-id CA+UBfa=SeR0svDvEADTwqPZPetxoTP7QXCSYhHsD_pK4y3P7yA@mail.gmail.com
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In response to Silence -Wmaybe-uninitialized warnings  (Imran Zaheer <imran.zhir@gmail.com>)
Responses Re: Silence -Wmaybe-uninitialized warnings
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Hi

I pulled the latest HEAD today and found some more -Wmaybe-uninitialized warnings. 

```
[1/6] Compiling C object src/interfaces/ecpg/test/pg_regress_ecpg.p/.._.._.._test_regress_pg_regress.c.o
../src/test/regress/pg_regress.c: In function ‘results_differ’:
../src/test/regress/pg_regress.c:1577:17: warning: ‘startpos’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 1577 |                 fseek(difffile, startpos, SEEK_SET);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[2/6] Compiling C object src/test/isolation/pg_isolation_regress.p/.._regress_pg_regress.c.o
../src/test/regress/pg_regress.c: In function ‘results_differ’:
../src/test/regress/pg_regress.c:1577:17: warning: ‘startpos’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 1577 |                 fseek(difffile, startpos, SEEK_SET);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[3/6] Compiling C object src/test/regress/pg_regress.p/pg_regress.c.o
../src/test/regress/pg_regress.c: In function ‘results_differ’:
../src/test/regress/pg_regress.c:1577:17: warning: ‘startpos’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 1577 |                 fseek(difffile, startpos, SEEK_SET);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```

Here is the updated v2 patch addressing them.


Regards,
Imran Zaheer


On Thu, Apr 2, 2026 at 2:49 PM Imran Zaheer <imran.zhir@gmail.com> wrote:
Hi

When building postgresql with CFLAGS="-Og" gcc emits
'-Wmaybe-uninitialized' warnings at few places. The variables are
initialized on all execution paths but the compiler was not able to
prove it with the additional optimization flag enabled. The patch
initializes the variables with NULL to silence the warnings. No
functional change intended.

```
[646/2085] Compiling C object
src/backend/postgres_lib.a.p/commands_copyfromparse.c.o
../src/backend/commands/copyfromparse.c: In function ‘CopyFromTextOneRow’:
../src/backend/commands/copyfromparse.c:995:39: warning:
‘field_strings’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
  995 |                 string = field_strings[fieldno++];
      |                                       ^
../src/backend/commands/copyfromparse.c:961:21: note: ‘field_strings’
was declared here
  961 |         char      **field_strings;
      |                     ^~~~~~~~~~~~~
../src/backend/commands/copyfromparse.c: In function ‘CopyFromCSVOneRow’:
../src/backend/commands/copyfromparse.c:995:39: warning:
‘field_strings’ may be used uninitialized in this function
[-Wmaybe-uninitialized]
  995 |                 string = field_strings[fieldno++];
      |                                       ^
../src/backend/commands/copyfromparse.c:961:21: note: ‘field_strings’
was declared here
  961 |         char      **field_strings;
      |                     ^~~~~~~~~~~~~
[889/2085] Compiling C object
src/backend/postgres_lib.a.p/partitioning_partbounds.c.o
../src/backend/partitioning/partbounds.c: In function
‘check_partition_bounds_for_split_range’:
../src/backend/partitioning/partbounds.c:5452:57: warning: ‘datum’ may
be used uninitialized in this function [-Wmaybe-uninitialized]
 5452 |
parser_errposition(pstate, exprLocation((Node *) datum)));
      |
```
gcc (Ubuntu 11.4.0-1ubuntu1~22.04.3) 11.4.0


Regards
Imran Zaheer
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