C constructs that still don't work in C++
1–10 of 182 posts
Re: C constructs that still don't work in C++
#2I wrote this after repeatedly seeing experienced C programmers hit the same sharp edges while moving into modern C++ codebases.
Many of these differences are intentional and defensible from the C++ side. But some are still surprising because they invalidate patterns that were historically common, performant, or idiomatic in C.
The interesting part to me isn’t "C vs C++," but where the languages diverged philosophically: object lifetime vs raw storage, stronger type systems, implicit conversions, ABI and optimization assumptions, and the boundary between "portable" and "works on my compiler."
I’d also be curious which C constructs people still genuinely miss in modern C++. For me, restrict is still near the top of the list.
Re: C constructs that still don't work in C++
#3From the article:
In 2019 I wrote a short survey of C constructs that do not
work in C++. The point was not that C is sloppy or that C++
is superior. The point was that C++ is not a superset of C,
and that C programmers crossing the border should know
where the checkpoints are.
Re: C constructs that still don't work in C++
#4Some unmentioned incompatibilities I've encountered that makes a C header not directly usable in C++:
- C `_Atomic(T)` and C++ `std::atomic`. C++23 has C compatible header `stdatomic.h` that defines `_Atomic(T)`, but it's still problematic
- C `_Noreturn/noreturn` and C++ `[[noreturn]]`. C23 `[[noreturn]]` makes them compatible
- C inline and C++ inline are different. Good news is their `static inline` are the same
- C has anonymous struct. C++ doesn't. Both have anonymous union though
Re: C constructs that still don't work in C++
#5From the article: In 2019 I wrote a short survey of C constructs that do not work in C++. The point was not that C is sloppy or that C++ is superior. The point was that C++ is not a superset of C, and that C programmers crossing the border should know where the checkpoints are. C++ was a superset of C 30-ish years ago. Now, as the author correctly identifies, it is not as both have taken different evolutionary paths.
Already in C++98 there were differences.
?: has another execution priority.
Implicit cast scenarios are reduced in C++.
Re: C constructs that still don't work in C++
#6I wrote this after repeatedly seeing experienced C programmers hit the same sharp edges while moving into modern C++ codebases. Many of these differences are intentional and defensible from the C++ side. But some are still surprising because they invalidate patterns that were historically common, performant, or idiomatic in C. The interesting part to me isn’t "C vs C++," but where the languages diverged philosophical…
Not sure if you're aware, but defer is proposed for C2Y [1]. It's already available in Clang behind a compiler flag. It is interesting how the languages continue to diverge.
[1] https://www.open-std.org/JTC1/SC22/WG14/www/docs/n3734.pdf
Re: C constructs that still don't work in C++
#7I wrote this after repeatedly seeing experienced C programmers hit the same sharp edges while moving into modern C++ codebases. Many of these differences are intentional and defensible from the C++ side. But some are still surprising because they invalidate patterns that were historically common, performant, or idiomatic in C. The interesting part to me isn’t "C vs C++," but where the languages diverged philosophical…
I appreciate that restrict isn't there, because it is yet another UB source, programmer knows not to do errors kind of attitude, and secondly no one seems to care enough to write a language proposal for it.
Re: C constructs that still don't work in C++
#8> restrict: a C promise, not a C++ contract
This takes the cake.
Re: C constructs that still don't work in C++
#9I wrote this after repeatedly seeing experienced C programmers hit the same sharp edges while moving into modern C++ codebases. Many of these differences are intentional and defensible from the C++ side. But some are still surprising because they invalidate patterns that were historically common, performant, or idiomatic in C. The interesting part to me isn’t "C vs C++," but where the languages diverged philosophical…
Not sure if you're aware, but defer is proposed for C2Y [1]. It's already available in Clang behind a compiler flag. It is interesting how the languages continue to diverge. [1] https://www.open-std.org/JTC1/SC22/WG14/www/docs/n3734.pdf
Because the communities aren't the same.
C++ is 1990's Typescript for C++, while C folks still think is a portable Assembly instead of designed to an abstract machine model.
As such C++ community embraces high level abstractions and type systems improvements, whereas C wants to still code as targeting classical hardware.
Re: C constructs that still don't work in C++
#10[deleted]