Trip report: June 2026 ISO C++ standards meeting (Brno, Czechia)

throwaway81523

The very first item listed jumped right out at me. "Complete catalog of all undefined behavior (UB) in C++". And further down, "Telecon line-by-line review of a proposal to systematically address all undefined behavior in C++": > "This was, pardon my French, a “[metric] ton” of work over the course of several years. Thanks Shafik, Joshua, Timur, Jens, and everyone who helped them compile this detailed catalog so that now we can next systematically do something about these UB cases!" I wonder if that already been done for C. Many whiners like to shout for a "safe" C or C++ dialect that's free of UB, but then deflect when asked how to specify such a thing. Listing all the ways to get UB is at least a start. Added: a UB-elimination rampage doesn't sound like a great idea to me, after hearing many calls e.g. to remove the signed-int overflow UB by defining signed arithmetic as 2s complement. That means (in a toy example of 4-bit integers) mandating that 5+5=-6 if I have it right. It's way preferable to do what Ada does and allow specifying the exact valid range of an integer type and mandating checked arithmetic. A compiler pragma could then allow an unsafe addition (maybe 2's complement) if you wanted to disable the check in in a hot loop or something. That's sort of what C does now, where the compiler can choose to signal an error on every occurrence of an int overflow (since it's UB, the compiler can do whatever it wants).