1468036 - RuntimeService::ClampedHardwareConcurrency() : Calling clampedHardwareConcurrency.compareExchange(0U, clampedValue) is only useful for its return value, which is ignored.

Status: RESOLVED FIXED

(Core :: DOM: Service Workers, defect, P2)

Description

[Sylvestre Ledru [:Sylvestre]]

Coverity thinks that  this line:
https://dxr.mozilla.org/mozilla-central/source/dom/workers/RuntimeService.cpp?q=clampedHardwareConcurrency.compareExchange&redirect_type=single#2565
is useless

It seems that it is the case as the implementation of compareExchange is:
  bool compareExchange(T aOldValue, T aNewValue)
  {
    return Intrinsics::compareExchange(mValue, aOldValue, aNewValue);
  }

Would mean that a few lines of code are not doing that they are supposed to.

Comment 1

[Sylvestre Ledru [:Sylvestre]]

Andrea, what do you think?

Comment 2

[Andrea Marchesini [:baku]]

Attachment: compare.patch

There is a comment to explain what that block of code does, but let's use Unused to make the static analysis happy.

Comment 3

[Sylvestre Ledru [:Sylvestre]]

I saw other similar occurrences, should it be fixed the same way?
https://dxr.mozilla.org/mozilla-central/source/xpcom/threads/nsMemoryPressure.cpp#43
https://dxr.mozilla.org/mozilla-central/source/ipc/glue/BackgroundImpl.cpp#1247
https://dxr.mozilla.org/mozilla-central/source/gfx/gl/GfxTexturesReporter.cpp?q=gfx%2Fgl%2FGfxTexturesReporter.cpp&redirect_type=direct#69

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/231d843c855b
Fix a warning in RuntimeService::ClampedHardwareConcurrency(), r=sylvestre

Comment 5

[Raul Gurzau (:RaulG)]

https://hg.mozilla.org/mozilla-central/rev/231d843c855b