Hi;
On 23/01/2018 17:13, Bryan Drewery wrote:
On 1/23/2018 11:40 AM, Pedro Giffuni wrote:
Hi;
On 23/01/2018 14:08, Conrad Meyer wrote:
Hi Pedro,
On Sun, Jan 21, 2018 at 7:42 AM, Pedro F. Giffuni <p...@freebsd.org>
wrote:
Author: pfg
Date: Sun Jan 21 15:42:36 2018
New Revision: 328218
URL: https://svnweb.freebsd.org/changeset/base/328218
Log:
Revert r327828, r327949, r327953, r328016-r328026, r328041:
Uses of mallocarray(9).
The use of mallocarray(9) has rocketed the required swap to build
FreeBSD.
This is likely caused by the allocation size attributes which put
extra pressure
on the compiler.
I'm confused about this change. Wouldn't it be better to remove the
annotation/attributes from mallocarray() than to remove the protection
against overflow?
Not in my opinion: it would be better to detect such overflows at
compile time (or through a static analyzer) than to have late
notification though panics. The blind use of mallocarray(9) is probably
a mistake also: we shouldn't use it unless there is some real risk of
overflow.
(If the compiler is fixed in the future to not use
excessive memory with these attributes, they can be conditionalized on
compiler version, of course.)
All in all, the compiler is not provably wrong: it's just using more
swap space, which is rather inconvenient for small platforms but not
necessarily wrong.
Pedro.
I haven't dug into this to understand it all, but if mallocarray() is
causing this sort of compilation problem then isn't the problem the
compiler? Why keep a "dangerous" function around and not actually fix
it? Is there a bug somewhere to fix the compilation load?
In all honesty .. I don't know what is going on. I theorize it may be
related to attributes but who knows.
I wouldn't say mallocarray(9) is dangerous, it's just not worth my time
specially since most of those multiplications have no chance of overflowing.
I will put up a patch with all the malloc --> mallocarray replacements
in case someone wants to spend time on it.
Pedro.
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