Unknown C++ braces syntaxis

Question

Look at this snippet:

void Sample_Compositor::createEffects(void)
{
    Ogre::CompositorPtr comp3 = Ogre::CompositorManager::getSingleton().create("Motion Blur", Ogre::ResourceGroupManager::DEFAULT_RESOURCE_GROUP_NAME);
    {
        {
            Ogre::CompositionTargetPass *tp = t->getOutputTargetPass();
            tp->setInputMode(Ogre::CompositionTargetPass::IM_NONE);
            {
                Ogre::CompositionPass *pass = tp->createPass();
                pass->setType(Ogre::CompositionPass::PT_RENDERQUAD);
                pass->setMaterialName("Ogre/Compositor/MotionBlur");
                pass->setInput(0, "sum");
            }
        }
    }
}

If this code is legit, how do these blocks work?

`{` starts a new block scope and `}` ends a block scope. It is fine to open a block to limit the scope of code. — James Adkison, May 28 '16 at 20:56
Is there a legitimate reason to down vote this question? (Lack or research?) — James Adkison, May 28 '16 at 21:00

score 2 · Accepted Answer · answered May 28 '16 at 20:56

2

They are simply blocks that introduce scope, and hide their contents. Perfectly valid.

answered May 28 '16 at 20:56

Paul Beckingham

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That's correct, thanks. – adflixit May 28 '16 at 21:07

score 2 · Answer 2 · answered May 28 '16 at 21:01

If s; is a valid statement, then so is { s; } and {{ s; }} and so on.

Adding redundant braces is perfectly legitimate, but entirely pointless.

The interesting question is why someone has written code this way. My guess is that the author is worried about exactly when local variables get destroyed. But almost all of the time that's the wrong thing to worry about - clarity of code trumps almost anything.

(There are occasionally times when apparently redundant braces are needed - in a switch statement, for example - but the code you show is not one of those.)

Unknown C++ braces syntaxis

2 Answers2