sdm7g@dale.acc.Virginia.EDU (Steve D. Majewski) (06/07/90)
** (apparent) PROBLEM WITH VMS (4.5) CRTL routine fstat() not free()ing
malloc()ed memory.
Since VMS does not have UNIX-y things like "tee file" to fork the output
to stdout & file, and I got tired of duplicating:
fprintf( stdout, ... );
fprintf( stderr, ... );
for all of the information that I wanted both on-screen and in a log-file,
I wrote a routine: stdprintf( same args as fprintf ), which prints to
(one, two, or all ) of ( stdout, stderr, & file ) - checking first that
they are not the same file ( as defined as having the same inode number ).
( OK - maybe this was overkill: I could have just made it duplicate output
to stdout & stderr, but I thought I might as well write a nice generalized
utility routine ..., etc. )
The routine calls fstat to get the inodes ( or in VMS: FID's ). The
terminal & _NLA0: ( and probably other non-file devices ) are all
FID(0,0,0), but that's OK as a restriction. It will do what I want
in most cases. ( MailBox:'s probably return the same. How about tape
file ? )
Basically, it works fine, except when I actually used it in my 30 hour data
acquisition program, it dies after logging ~2000 points. First I get a
"PAGE FILE FRAGMENTED" message on the console and eventually it dies with an
access violation. Debugging at this stage is like molasses of course !
It appears that memory is being allocated and not being deallocated, and
things seem to point to those fstat calls. I can see the virtual page
count grow with "show proc /cont". fstat DOES call malloc, but I have been
unable to confirm more that that.
*Q1) Can anyone confirm that "fstat" is in fact the culprit ?
*Q2) Is this feature removed in a leter version of VMS/CRTL/fstat ?
I suppose that the OTHER way of doing something like this in VMS would be
a process that reads its mailbox ( or pipe ) and forks it's output to
a file & stdout. The VMS-ese equivalent ( of UNIX:
"program args | tee file | more ") would be something like:
"TEE file Program-to-spawn [ and it's args ... ]"
*Q3) Has anyone done this ? *Q4) Does anyone have a suggestion ?
And a somewhat unrelated question: You can go from *FILE to (int)
file-descriptor with fileno(). (How) Can you do the reverse ?
( and can you map either of the above to RMS $FAB's without doing
a RMS$OPEN ? )
*** NOTE: system is VMS 4.5, VaxStationII, 3MB memory.
Since starting to write this note, I'm running a test with my
same_file() routine always returning TRUE & the fstat calls commented out.
It got past 4000 points without dieing so far, so I'm willing to
believe the initial diagnosis. The immediate fix if to probably
keep a static table of inodes/FIDs and only call fstat ONCE per file.
- Steve Majewski / UVA Physiology
sdm7g@virginia.edudaniels@hanoi.enet.dec.com (Bradford R. Daniels) (06/15/90)
The problem is that fstat() calls getenv(), which allocates memory for its return value. There is a fixed version of getenv() which keeps around old results so that it doesn't need to allocate memory every time. It will be available in "a future release of VMS", no doubt... Your work-around is the best solution for now. - Brad ----------------------------------------------------------------- Brad Daniels | Digital Equipment Corp. almost DEC Software Devo | definitely wouldn't approve of "VAX C RTL Whipping Boy" | anything I say here...