docs: cxx_runtime was inert on MSVC until 2026.8.16, and upgrading is silent - #450
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… silent The MSVC section describes today's behaviour correctly and says nothing about the fact that it is NEW. Through 2026.8.15 the key reported "not implemented for the MSVC runtime yet" and every value fell back to /MD; since 2026.8.16 (#422) it selects the CRT model. So a manifest carrying `cxx_runtime = "self-contained"` from that era switches from /MD to /MT on upgrade — silently, because the value was always spelled correctly and always accepted. /MT is a different CRT model rather than a stricter version of the same one. Not hypothetical: found while reviewing xrgui's mcpp manifest, which carried exactly that value, set at a time when it did nothing, with a comment explaining that it was a no-op.
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The MSVC section of
05-mcpp-tomldescribes today's behaviour correctly and says nothing about the fact that it is new.Through 2026.8.15 the key reported
not implemented for the MSVC runtime yetand every value fell back to/MD; since 2026.8.16 (#422) it selects the CRT model. So a manifest carryingcxx_runtime = "self-contained"from that era switches from /MD to /MT on upgrade — silently, because the value was always spelled correctly and always accepted, and/MTis a different CRT model rather than a stricter version of the same one.Not hypothetical. Found while reviewing xrgui's mcpp manifest, which carried exactly that value — set while the key did nothing, with a comment explaining that it was a no-op:
That project wants
/MD(it matches its xmake build), so the value there is being corrected tohost-coupledon its side. This adds the note for everyone else in the same position.Docs only, en + zh.