svn commit: r328218 - in head/sys: amd64/amd64 arm/xscale/ixp425 arm64/arm64 cam cam/ctl compat/ndis dev/aacraid dev/advansys dev/ath dev/beri/virtio dev/bnxt dev/bwn dev/ciss dev/cxgbe/crypto dev/...

[Bryan Drewery]

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 <pfg at 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?

-- 
Regards,
Bryan Drewery

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