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178 points todsacerdoti | 1 comments | 04 Mar 21 08:02 UTC | HN request time: 0.208s | source

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TonyTrapp ◴[04 Mar 21 09:30 UTC] No.26340399[source]▶

Don’t blindly prefer emplace_back to push_back*

*when using it incorrectly. The premise of of emplace_back is that you use it for calling the constructor of the object in place. Obviously it won't help you if you call a copy constructor instead. I find this article a bit pointless. Clang's suggestion was spot-on and emplace_back would have (potentially) helped if the suggestion was actually followed correctly.

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pdpi ◴[04 Mar 21 09:44 UTC] No.26340494[source]▶

>>26340399 #

Hence “blindly”. The blog post was a detailed, less sanctimonious version of your comment.

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1. IshKebab ◴[04 Mar 21 10:00 UTC] No.26340605[source]▶

>>26340494 #

Yeah but the title sounds like "you shouldn't just always use emplace_back instead of push_back" but the actual content is "you shouldn't use emplace_back completely incorrectly because you don't know what it is".

The only actual argument against blindly using emplace_back everywhere is that it has worse compile time in a deliberately pathological microbenchmark. Not convincing, though it is interesting.

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