Sender: jennrich AT onehertz DOT Colorado DOT EDU
To: pgcc AT delorie DOT com
Subject: Something hogs memory...
From: Oliver Jennrich <oliver DOT jennrich AT colorado DOT edu>
Date: 19 Aug 1999 11:51:25 -0600
Message-ID: <m3672bk6aq.fsf@onehertz.Colorado.EDU>
Lines: 82
X-Mailer: Gnus v5.6.45/XEmacs 21.1 - "20 Minutes to Nikko"
Reply-To: pgcc AT delorie DOT com


Hi folks,

first of all, I'm not on the list, so any 'cc:' to me would be greatly
appreciated.

I think I discovered a bug, although I'm not sure that it is *really*
a pgcc bug, but then, gcc.486 does not show this behaviour.

It is kind of complicated because it involves NAG's Fortran95 (no it
is *not* their bug). The string concatenation hogs memory. This is
easily demonstrated by the following code:

Program MEMTEST
  !
  !  Shows a memory leak when compiled with NAG f95 compiler.
  !
  use f90_unix_env
  use f90_unix_proc
  !
  character                :: command*32, text,dummy*32
  integer                  :: pid
  !
  open(8,file='/dev/null')
  pid=getpid()                       ! get process ID
  write(command,'(i10)') pid
  command='ps vp '//command
  do n=1,100
     write(8,*) 'sample ',n
     do i=1,10000
        text=' '                       
        text=trim(text)//' abc'      ! HOG
        write(8,'(a)') text
     end do
     if (n == 1) call system(command) ! memory after first inner loop
  end do
  call system(command)               ! memory after last inner loop
  !
end program memtest

Depending on the existence of the line marked 'HOG' the program
allocates huge amounts of mem.

With HOG:
  PID TTY STAT TIME  PAGEIN TSIZ DSIZ  RSS   LIM %MEM COMMAND
29144  ?  S    0:00     155   32 1343  536    xx  0.4 ./memtest 
  PID TTY STAT TIME  PAGEIN TSIZ DSIZ  RSS   LIM %MEM COMMAND
29144  ?  S    0:04     155   32 5211 4404    xx  3.4 ./memtest 

Without HOG:
  PID TTY STAT TIME  PAGEIN TSIZ DSIZ  RSS   LIM %MEM COMMAND
29155  ?  S    0:00     123   31 1304  492    xx  0.3 ./memtest 
  PID TTY STAT TIME  PAGEIN TSIZ DSIZ  RSS   LIM %MEM COMMAND
29155  ?  S    0:02     123   31 1304  492    xx  0.3 ./memtest 

You might argue that this is not a bug at all, but then, using the
gcc.486 as the C-Compiler NAG_f95 uses, it becomes:

  PID TTY STAT TIME  PAGEIN TSIZ DSIZ  RSS   LIM %MEM COMMAND
29166  ?  S    0:00     126   31 1304  504    xx  0.3 ./memtest 
  PID TTY STAT TIME  PAGEIN TSIZ DSIZ  RSS   LIM %MEM COMMAND
29166  ?  S    0:04     126   31 1304  504    xx  0.3 ./memtest 

with and without the HOG-line.

For those of you not familiar with Fortran-syntax: '//' concatenates
strings, much as strcat() does.

The compilers in question are:
gcc version pgcc-2.91.66 19990314 (egcs-1.1.2 release)
and
gcc version 2.7.2.3  

If it is of any help I can provide anyone with the preprocessed
.i-Files andør the preprocessed C files, f95 produces.



-- 
Oliver Jennrich		JILA, University of Colorado @ Boulder

Gravity. It's not just a good idea, it's the law!