Re: more compile warnings

-----Original Message-----
From: Bruce Momjian [mailto:pgman@candle.pha.pa.us]
Sent: Friday, December 06, 2002 7:58 PM
To: Joe Conway
Cc: rbt@zort.ca; PostgreSQL-development
Subject: Re: [HACKERS] more compile warnings

Rod, can you comment on these warnings Joe Conway's compiler
is showing? I don't see the warnings with gcc, but clearly
they look like problems.

I can just assign a NULL on definition, but I thought you
should take a look.

--------------------------------------------------------------
-------------

Joe Conway wrote:

Hi Bruce,

I just sync'd up/make clean/make all and get this:

gcc -O2 -g -Wall -Wmissing-prototypes -Wmissing-declarations
-I../../../src/include -c -o typecmds.o typecmds.c -MMD
typecmds.c: In function `AlterDomainAddConstraint':
typecmds.c:1237: warning: `ccbin' might be used

uninitialized in this

function
typecmds.c: In function `get_rels_with_domain':
typecmds.c:1450: warning: `rtc' might be used uninitialized

in this function

Instead of just assigning a value, it means it is conceivable that a
path allows undefined behavior. Example:

...
int y;
if (x < 5)
y = 3;
if (x > 5)
y = 1;

What happens if x == 5? Then y is indeterminate.

Sometimes, the flow analysis just gets confused and it really will be
initialized along every path. But at least it bears checking. Hence
the warning.

I like to use -W -Wall -ansi -pedantic -O3

Dann Corbit wrote:

Instead of just assigning a value, it means it is conceivable that a
path allows undefined behavior. Example:

...
int y;
if (x < 5)
y = 3;
if (x > 5)
y = 1;

What happens if x == 5? Then y is indeterminate.

Sometimes, the flow analysis just gets confused and it really will be
initialized along every path. But at least it bears checking. Hence
the warning.

Yes, I looked at the code, and they are legitimate warnings.

I like to use -W -Wall -ansi -pedantic -O3

I use:

-Wall -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wcast-align

You would think that would catch it. My problem is that I am compiling
with -O0, because I compile all day and I don't care about optimization.
In this case, the -O3 is doing some optimization that catches the
problem, while -O0 does not. Interesting. Even -O catches it.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

On Fri, Dec 06, 2002 at 11:16:30PM -0500, Bruce Momjian wrote:

I use:

-Wall -Wmissing-prototypes -Wmissing-declarations -Wpointer-arith -Wcast-align

Some other useful ones are -pedantic -W -Wfloat-equal -Wshadow
-Wcast-qual -Wwrite-strings -Wconversion -Wsign-compare -Wsign-promo.

You would think that would catch it. My problem is that I am compiling
with -O0, because I compile all day and I don't care about optimization.
In this case, the -O3 is doing some optimization that catches the
problem, while -O0 does not. Interesting. Even -O catches it.

Last time I checked (which was admittedly some time ago) all the
interesting analysis that could give you new warnings was done by -O;
-O2 mostly involves the back-end, and -O3 adds pretty much nothing
except aggressive inlining. Which was more likely to trigger compiler
bugs at the time than to find anything in your code.

Jeroen

Bruce Momjian <pgman@candle.pha.pa.us> writes:

You would think that would catch it. My problem is that I am compiling
with -O0, because I compile all day and I don't care about optimization.

You should reconsider that. At -O0 gcc doesn't do any flow analysis,
and thus you lose many important warnings. I'd recommend -O1 at least.

regards, tom lane

Tom Lane wrote:

Bruce Momjian <pgman@candle.pha.pa.us> writes:

You would think that would catch it. My problem is that I am compiling
with -O0, because I compile all day and I don't care about optimization.

You should reconsider that. At -O0 gcc doesn't do any flow analysis,
and thus you lose many important warnings. I'd recommend -O1 at least.

Yes, I will re-add -O to my flags. When I did it I forgot it would
affect warnings. In fact, I am now seeing a similar warning in python
that I hadn't seen before, and others probably don't see it because they
don't compile python.

FYI, -O2 adds only 2 minutes to my 13 minute test script (but increases
the cpu usage from 4 to 6 minutes).

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073