> -----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

Fri, 6 Dec 2002 20:10:20 -0800
"Dann Corbit" <DCorbit@connx.com>
Re: more compile warnings
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

Fri, 6 Dec 2002 23:16:30 -0500 (EST)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: more compile warnings
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


Sat, 7 Dec 2002 05:35:11 +0100
"Jeroen T. Vermeulen" <jtv@xs4all.nl>
Re: more compile warnings
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

Sat, 07 Dec 2002 16:14:37 -0500
Tom Lane <tgl@sss.pgh.pa.us>
Re: more compile warnings 
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

Mon, 9 Dec 2002 13:42:23 -0500 (EST)
Bruce Momjian <pgman@candle.pha.pa.us>
Re: more compile warnings