Re: malloc() exceeds RLIMIT_DATA

[David Holland <dholland-tech%netbsd.org@localhost>]

On Tue, Jul 09, 2019 at 10:24:53AM -0700, Graham Percival wrote:
 >     RLIMIT_DATA
 >     This is the maximum size of a data segment of the process, in bytes. If
 >     this limit is exceeded, the malloc() function shall fail with errno set to
 >     [ENOMEM].
 >     http://pubs.opengroup.org/onlinepubs/9699919799/functions/getrlimit.html
 > 
 > The relevant part is the second sentence.  My interpretation of that sentence
 > is that if malloc() does *not* fail when it is asked to exceed RLIMIT_DATA,
 > then it is not following the POSIX standard.

Ah, but how do you ask malloc to exceed RLIMIT_DATA? Not by passing it
a large number, or any number, since that doesn't change the size of
any data segment.

I think a program image whose .data exceeds RLIMIT_DATA won't load, so
in that case any call to malloc will indeed fail with errno set to
ENOMEM, inasmuch as anything follows from an invalid premise.

Although now I wonder if ld.so enforces RLIMIT_DATA on the .data size
of shared library images.


(Note: if you're trying to do something practical, you might find
RLIMIT_AS or RLIMIT_RSS more helpful.)

-- 
David A. Holland
dholland%netbsd.org@localhost