Thread: not checking value returned from palloc?
Looking through the postgresql source code, I notice that there are many places
were palloc is used but the return value is not checked to see if it is null.
There are a few places such as:
if (!PointerIsValid(result = palloc(CASH_BUFSZ + 2 - count + strlen(nsymbol)))) ereport(ERROR,
(errcode(ERRCODE_OUT_OF_MEMORY), errmsg("out of memory")));
(taken from src/backend/utils/adt/cash.c), but at least within the that same
directory most occurrences of palloc are not checked.
Is this sloppy programming, or is there an automagical thing going on with
#defines that I'm just not seeing?
If it is just sloppy, perhaps we could use a new define in palloc.h, such as:
#define palloc_or_die(ptr,sz) \do { \ ptr = palloc(sz); \ if (!ptr) \ { \ ereport(ERROR, \
(errcode(ERRCODE_OUT_OF_MEMORY),\ errmsg("Out of memory"))); \ } \} while(0);
And then, in all places where the code does not currently check the return value
of palloc, the code could be changed to use palloc_or_die instead. Of course,
I'd be happy if someone has a better name for the macro, perhaps something more
brief?
I can go over the code "with a fine tooth comb" and replace the offending
occurrences. Does the community think this is a good idea?
mark
Mark Dilger wrote: > Looking through the postgresql source code, I notice that there are > many places were palloc is used but the return value is not checked > to see if it is null. palloc will throw an exception if it cannot fulfill the request. Code that checks the return value for null is in fact a waste. -- Peter Eisentraut http://developer.postgresql.org/~petere/
Mark Dilger <pgsql@markdilger.com> writes:
> Looking through the postgresql source code, I notice that there are many places
> were palloc is used but the return value is not checked to see if it is null.
Any place that *does* check it is incorrect (in the sense of being
wasted code space, not functionally incorrect). Please read the memmgr
documentation.
regards, tom lane
Peter Eisentraut wrote: > Mark Dilger wrote: > >>Looking through the postgresql source code, I notice that there are >>many places were palloc is used but the return value is not checked >>to see if it is null. > > > palloc will throw an exception if it cannot fulfill the request. Code > that checks the return value for null is in fact a waste. > Interesting. So the patch should go the other way, and remove the checks that are currently in the code?
Mark Dilger wrote: > Peter Eisentraut wrote: > >Mark Dilger wrote: > > > >>Looking through the postgresql source code, I notice that there are > >>many places were palloc is used but the return value is not checked > >>to see if it is null. > > > >palloc will throw an exception if it cannot fulfill the request. Code > >that checks the return value for null is in fact a waste. > > Interesting. So the patch should go the other way, and remove the checks > that are currently in the code? Yes, if you find any such place please submit a patch. -- Alvaro Herrera http://www.CommandPrompt.com/ PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Alvaro Herrera wrote: > Mark Dilger wrote: > > Peter Eisentraut wrote: > > >Mark Dilger wrote: > > > > > >>Looking through the postgresql source code, I notice that there are > > >>many places were palloc is used but the return value is not checked > > >>to see if it is null. > > > > > >palloc will throw an exception if it cannot fulfill the request. Code > > >that checks the return value for null is in fact a waste. > > > > Interesting. So the patch should go the other way, and remove the checks > > that are currently in the code? > > Yes, if you find any such place please submit a patch. I see one in cash.c that I will remove. -- Bruce Momjian http://candle.pha.pa.us SRA OSS, Inc. http://www.sraoss.com + If your life is a hard drive, Christ can be your backup. +
On Sun, 2006-03-19 at 17:14 -0500, Bruce Momjian wrote: > I see one in cash.c that I will remove. I've already checked in a fix for that, as well as a few other places that made similar mistakes -- sorry for stepping on your toes. -Neil