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.
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