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If you want to get people using a Friendly C, you need to start convincing the biggest users of C and C++ that they should give up performance for a simpler dia

by nkurz 11y ago

If you want to get people using a Friendly C, you need to start convincing the biggest users of C and C++ that they should give up performance for a simpler dialect of the language. Why would would C++ programmers have to give up anything? You may notice that the frequent complaint (and title of the article) is "undefined behavior in C", and the hypothetical replacement language is "Friendly C", not "Friendly C++". From the point of view of most who are troubled, rightly or wrongly, C++ isn't considered relevant to the problem or the solution. I think part of the "divide" is that compiler writers (and probably C++ programmers) are more likely to lump C and C++ together. This makes sense, as C++ is mostly a superset of C, and since many of the optimizations being questioned operate at the level of internal intermediate language that's the same for both. But many C programmers don't view them as being the same language at all, and have no opinion on how C++ compilers should operate. Perhaps what needs to be questioned is assumption that the needs of C and C++ programmers can effectively be served by the same compiler? (I realize I've responded strongly to two of your comments in a row. I care strongly about the issue, but don't intend this to be an attack. Rather trying to convince you that you're wrong, my goal is just to understand what produces the gap between our viewpoints.)

pcwalton 11y ago
Do you have any UB-sensitive optimizations in mind that affect only C but not C++, or vice versa? I can't really think of any.
- nkurz 11y ago
  Do you have any UB-sensitive optimizations in mind that affect only C but not C++, or vice versa? I presume there are some, but they aren't the sort of thing I have in mind. I'm talking more about the expectations that the users of each language have. For whatever reason, C programmers are much more likely to complain about "broken" optimizations than are C++ programmers. Of course this isn't absolute, but I think it's undeniably a pattern. I'd guess this is because C has a heritage of being "portable assembly", and thus many programmers have an expectation of a 1:1 correspondence between the code they write and the finished product, and are startled when it doesn't. In the case of explicit null checks being removed and loops being removed resulting in memory not being zeroed, I think they have a point. Perhaps there is some way to apply different levels of optimization to the code that the programmer writes versus code "generated" code?

by nkurz 11y ago

pcwalton 11y ago

Do you have any UB-sensitive optimizations in mind that affect only C but not C++, or vice versa? I can't really think of any.

nkurz 11y ago
Do you have any UB-sensitive optimizations in mind that affect only C but not C++, or vice versa? I presume there are some, but they aren't the sort of thing I have in mind. I'm talking more about the expectations that the users of each language have. For whatever reason, C programmers are much more likely to complain about "broken" optimizations than are C++ programmers. Of course this isn't absolute, but I think it's undeniably a pattern. I'd guess this is because C has a heritage of being "portable assembly", and thus many programmers have an expectation of a 1:1 correspondence between the code they write and the finished product, and are startled when it doesn't. In the case of explicit null checks being removed and loops being removed resulting in memory not being zeroed, I think they have a point. Perhaps there is some way to apply different levels of optimization to the code that the programmer writes versus code "generated" code?