Enhance /std documentation with reference to /Zc:__cplusplus - #5010

William S Fulton (@wsfulton) : Thanks for your contribution! The author(s) have been notified to review your proposed change.

Learn Build status updates of commit 113ee82:

✅ Validation status: passed

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

Tyler Whitney (@TylerMSFT)

Can you review the proposed changes?

When the changes are ready for publication, add a #sign-off comment to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

William S Fulton (@wsfulton) : Thanks for your contribution! The author(s) have been notified to review your proposed change.

Learn Build status updates of commit 3059e82:

✅ Validation status: passed

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

Learn Build status updates of commit 1356b99:

✅ Validation status: passed

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

#sign-off

Learn Build status updates of commit 8c8f2dc:

💡 Validation status: suggestions

docs/build/reference/std-specify-language-standard-version.md

• Line 34, Column 3: [Suggestion: table-syntax-invalid - See documentation] Table syntax is invalid. Ensure your table includes a header and is surrounded by empty lines.

For more details, please refer to the build report.

Note: Your PR may contain errors or warnings or suggestions unrelated to the files you changed. This happens when external dependencies like GitHub alias, Microsoft alias, cross repo links are updated. Please use these instructions to resolve them.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

Thank you, Tyler Whitney (@TylerMSFT)!

Learn Build status updates of commit c54b897:

✅ Validation status: passed

For more details, please refer to the build report.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

Thanks Tyler Whitney (@TylerMSFT), wonderful that this information can be conveyed on the /std documentation page and the reformulated wording is much better than the current official documentation which omits this important information.

However, I do feel that the simple one sentence I proposed is perhaps clearer, more relevant and succinct for the /std page. The primary simple message on the /std page is that one should seriously look at adding in the /zc:__cplusplus option and look at the documentation on this page.

I'm not sure repeating the details of the exact values of __cplusplus from the /zc:__cplusplus page is a good idea, I would leave them on that page and keep a simple link to it.

The reasons you added for not setting __cplusplus according to that mandated by the standard is very useful, but again, getting bogged down with the values in the /std page doesn't seem right and is best left on the /zc:__cplusplus page.

Obviously it would be the right thing if /std did the right thing and was truly standards conforming, but as this is not the case chosen by the MSVC developers, a simple succinct fix for this omission is what a user is interested in and is what the documentation should aim for.

I would suggest this combination:

[!IMPORTANT]
The [`/Zc:__cplusplus`](zc-cplusplus.md) option must additionally be used for the `__cplusplus` macro to be correctly defined for the appropriate C++ standard.
Without the addition of `/Zc:__cplusplus`, the value of the `__cplusplus` macro is hard wired to 199711L (c++98) in order to support some existing code that depends on this macro being set to this value.

We can't tell people they have to set it and then not tell them to what, or hope they go to another topic to find the info. I'll keep the table.

Tyler Whitney (@TylerMSFT), I am sorry, but am a confused by the last comment as users don't need to set the value of __cplusplus, the value is set automatically via a combination of /std and /Zc:__cplusplus options.

If you feel a table is needed on the /std page, then please consider copying the table from the zc-cplusplus.md page, because in comparison:

1. it is technically accurate - does not miss the L suffix.
2. it is complete - contains 3 additional rows including /std:c++latest.
3. and most importantly, by using 3 columns, is unambiguously and absolutely clear what the __cplusplus value is for all combinations of the two options.

I see what you are saying. I update this in PR #5538

Excellent, thanks, I found the commit to main here: 2e67cbc