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The biggest question I have around the viability of breaking changes in C++ is whether you can compile some code with a newer breaking standard, some with an ol

The biggest question I have around the viability of breaking changes in C++ is whether you can compile some code with a newer breaking standard, some with an older standard, and link them. Headers would be a problem given their text inclusion in multiple translation units, but it's not insurmountable; you're currently limited to the oldest standard a header is included into, and under a new standard that breaks compatibility you'd be limited to a valid subset of the old & new standard. EDIT: ironically modules (as a concept) would (could?) solve the header problem, but they've not exactly been a success story so far.

TuxSH 1y ago
> EDIT: ironically modules (as a concept) would (could?) solve the header problem, but they've not exactly been a success story so far. Because they are little different from precompiled headers. Import std; may be nice, but in a large project you are likely to have your own defines.hpp file anyway (that is going to be precompiled for double-digits compile times reduction). Ironically too, migrating every header in an executable project to modules might slow down build times, as dependency chains reduce the parallelism factor of the build.
steveklabnik 1y ago
There was a proposal for “epochs” (the feature that rust calls “editions” now) but they were effectively rejected by the committee. Not permanently, but there’s some questions that need to be addressed that they initial proposers aren’t interested in following up on, in my understanding.