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SL.io.50 (Avoid endl): Mention string streams #1920

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Merged
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Jun 13, 2022
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SL.io.50 (Avoid endl): Mention string streams #1920

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8 changes: 8 additions & 0 deletions CppCoreGuidelines.md
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Expand Up @@ -20308,6 +20308,14 @@ For writing to a file, there is rarely a need to `flush`.

##### Note

For string streams (specifically `ostringstream`), the insertion of an `endl` is entirely equivalent
to the insertion of a `'\n'` character, but also in this case, `endl` might be significantly slower.

`endl` does *not* take care of producing a platform specific end-of-line sequence (like "\r\n" on
Windows). So for a string stream, `s << endl` just inserts a *single* character, `'\n'`.
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or \n\r for Mac ;)

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or \n\r for Mac ;)

@BenjamenMeyer You mean '\r', right? But hasn't Mac moved towards using just a single \n, nowadays? Otherwise, are there still actively used C++11 Standard Library implementations for Mac whose file output streams produce a '\r' on each end-of-line?

I did notice the smiley in your comment, but I just want to be entirely sure that it's OK not to mention the old Mac '\r' in the proposed text.

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@N-Dekker AFAIK mac is still doing the \n\r - now, perhaps it changes from application to application, but I've still seen it in recent years. The new text called out the Windows behavior as an example; it could be worth noting (legacy or otherwise) the Mac behavior too.

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I just want to be entirely sure that it's OK not to mention the old Mac '\r' in the proposed text.

Please don't mention Macs. Your proposed change is fine. What matters is that it doesn't output a platform-specific line ending, you don't need to give multiple examples of things it doesn't do.

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I'm fine with this PR documenting it ;) (e.g not a change - just the commentary here)

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@jwakely @BenjamenMeyer Thanks, I won't mention old Macs line endings, if it isn't really necessary. So I also think the PR is OK now.


##### Note

Apart from the (occasionally important) issue of performance,
the choice between `'\n'` and `endl` is almost completely aesthetic.

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1 change: 1 addition & 0 deletions scripts/hunspell/isocpp.dic
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Expand Up @@ -389,6 +389,7 @@ optimizable
O'Reilly
org
ostream
ostringstream
overabstract
overconstrain
overconstrained
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