[swift-corelibs-dev] Encountering "Constant strings cannot be deallocated" in Linux foundation

Brandon Williams mbw234 at gmail.com
Wed Nov 29 16:06:40 CST 2017

Thanks for the info!

FWIW, most of the places I have encountered this so far have made use of
`URLComponents`, and have even been able to eliminate the crash by getting
rid of that code in a few places. The other JIRA bug on this topic also
mentions URLComponents in their repro case. Seems to be the culprit.

Also worth noting that in the above cases dealing with URLComponents the
crash only happens in DEBUG compilations, not RELEASE.

However, I do have another one of these crashes that _does_ happen on
RELEASE builds that I haven’t yet been able to reduce.

On Wed, Nov 29, 2017 at 4:43 PM Tony Parker <anthony.parker at apple.com>

> Hi Brandon,
> This is probably a bug in the CoreFoundation C sources part of
> swift-corelibs-foundation. Unlike Darwin platforms, we can’t make the
> CFSTR(“”) macro produce a CFStringRef that cannot be overreleased. Probably
> there is a constant string returned from CF function, then the Swift
> runtime assumes it can release it, and bam we wind up with an overrelease.
> We’ll have to track down which function is getting called, which probably
> just requires stepping through that test case with a debugger…
> - Tony
> On Nov 29, 2017, at 1:34 PM, Brandon Williams via swift-corelibs-dev <
> swift-corelibs-dev at swift.org> wrote:
> Hello all!
> We’ve been encountering this runtime error quite a bit recently, and we
> have no idea why. We’ve filed a bug and there’s one other on JIRA related
> to this, but both without any comments:
> https://bugs.swift.org/browse/SR-6422
> https://bugs.swift.org/browse/SR-6398
> We’re curious if others are aware of this and or has more info? Is it a
> red herring for some other problem?
> Any info would be helpful!
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