Re: [libvirt] [PATCH v4 RESEND 1/4] threadpool impl
On 12/02/2010 05:28 AM, Daniel P. Berrange wrote:
> +virThreadPoolPtr virThreadPoolNew(size_t minWorkers,
> + size_t maxWorkers,
> + virThreadPoolJobFunc func,
> + void *opaque) ATTRIBUTE_NONNULL(3)
> + ATTRIBUTE_RETURN_CHECK;
ATTRIBUTE_RETURN_CHECK doesn't serve any useful purpose
when placed on constructors, since the caller will always
"use" the return value by assigning the pointer to some
variable. The compiler can thus never detect whether you
check for null or not, even with this annotation.
Good point. However, in looking through gcc's documentation, maybe it's
time we introduce a new attribute for constructors:
#define ATTRIBUTE_MALLOC __attribute__((__malloc__))
The `malloc' attribute is used to tell the compiler that a function
may be treated as if any non-`NULL' pointer it returns cannot
alias any other pointer valid when the function returns. This
will often improve optimization. Standard functions with this
property include `malloc' and `calloc'. `realloc'-like functions
have this property as long as the old pointer is never referred to
(including comparing it to the new pointer) after the function
returns a non-`NULL' value.
I think that tools like clang might also be able to feed off of the
malloc attribute to make decisions about whether NULL-checking needs to
be performed on the result, and/or provide better leak detection analysis.
However, that's a separate idea, and doesn't affect this series.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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