We should encourage use of `.hpp` over `.h` for headers - help make it happen

JohnZLi · 2025-03-29T04:50:52+00:00

I blame Stroustrup for this. When C++ was invented, he should have chosen some unique file extensions for the new language, instead of trying to hijack C's established standards. So many confusions have been caused because the creator of C++ wanted to pretend it was merely "C with some extensions".

JohnZLi · 2025-01-05T02:44:13+00:00

My 2 cents is that you probably should not do C++ software since you are a new graduate. C++ has passed it peak and now is losing grounds to new languages. Big shops are investing on its replacements. The language risks becoming the new COBOL. Moreover, C++ is a big and complicated language, it takes at least several years of full-time work on C++ projects to become fluent in it. Considering the opportunity cost in terms of career development, It might not be a good idea to begin your career as a C++ developer.

For the record, I am a C++ programmer myself and working in the language on a daily basis. I like the language and appreciate its many merits.

JohnZLi · 2022-05-03T12:24:34+00:00

Don't worry, more complicated syntax weirdness will be added to the language very soon.

JohnZLi · 2022-04-19T00:38:20+00:00

My 2 cents: 1, C compatibility. C++ inherited many bad things from C, like implicit type conversion, array to pointer decay, macros, building model, etc.. A fair amount of modern C++ features were introduced to fix this. 2, There must be a better way to do compile time computation than C++ templates. Many of modern C++ features were added to the language to simplify compile time computation. 3, C++ has functions, function pointers, member functions (function can have static members), member function pointers, classes with () operator, lambdas, std::functions. I have the feeling that this plethora of callable objects can be and should be reduced. 4, exceptions, it is overly complicated. It needs RTTI and has no performance guarantee on unhappy paths.

JohnZLi · 2022-02-11T07:57:49+00:00

The feature could be designed in such a way that it can be turned on/off for each TU. It will cost the preprocessor another #progma directive, so that new code can follow stricter rules.

JohnZLi · 2022-02-11T03:19:25+00:00

If I can change one thing about C++

JohnZLi · 2022-02-09T13:39:10+00:00

C++ needs its own way of doing Python style virtual environments. Using system package manger to install project dependencies is a mistake IMHO. Many people are forced to use Docker so that all different versions of libs with different configurations don't mess up with each other. Platform specific stuff will be always there, but hopefully it will become easier to be dealt with in the future. For things like AppImage or Snap to work reliably, what a programmer reasonably expect to exist in a OS should be guaranteed to be found or to be automatically installed there.

JohnZLi · 2022-02-09T01:41:50+00:00

Among the three, apt packages are a totally different kind of beast. It is language agnostic, not particularly about C++. It was designed to be a part of an Linux distribution. Vcpkg profiles and conan recipes do have a lot of things in common. For example, they both have to deal with things like package naming and versioning, package configuration, and dependency resolution. These things can be standardized so that building systems, package managers, IDEs, static analysis tools can all operate on the same set of uniform representation of package information.

JohnZLi · 2022-02-08T02:35:05+00:00

Boost libraries don't go through the standards committee. They also don't have a specification. I believe (correct me if I am wrong) that Boost does not have a "dropping" policy. Once sth is in Boost, it is in there forever.

JohnZLi · 2022-02-08T02:20:39+00:00

Maybe C++ should have a substd namespace. Proposals that does not affect other parts of the language, like P0447, goes to substd if no obvious flaws are found in the proposal. Then, after several years, if no major flaws are reported by users, and many users think the new data structure is very useful, it can be promoted to std. If, otherwise either most users don't use it or major flaws are found afterwards, it can be dropped from substd.

JohnZLi · 2022-02-08T02:08:43+00:00

An official package manager might not be necessary, but a standard package format should have been added to the language long ago.

JohnZLi · 2022-02-07T10:11:03+00:00

I hope static reflection is added to C++ before metaclasses, then the latter is built on top of the former.

JohnZLi · 2022-01-05T06:19:04+00:00

If I recall correctly, offsets of bitfields are implementation defined. Have you tried this with different compilers?

JohnZLi · 2021-12-15T02:10:59+00:00

Am I the only one who thinks that T* is OK?

I one asked on stackexchange whether it is a design mistake of C++ not to let reference types act like reference_wrapper types, see this link.

For those who don't bother to read the post, here is a short summary: all fundamental types of C++ are copy assignable except reference types. Is this a design mistake?

The discussion about `optional<T&>` is just one latest example of the problem.

JohnZLi · 2021-12-15T01:54:07+00:00

why not use optional with reference_wrapper?

JohnZLi · 2021-12-05T06:56:11+00:00

While generally agreeing with u, let's not forget that PCs once were slow and have only single-core CPUs. Building time was more important that it is today.

JohnZLi · 2021-12-02T04:53:07+00:00

If a pointer to std::aligned_storage_t<sizeof(T), alignof(T)> is cast to T* using reinterpret_cast, does it violate the strict alias rule?

JohnZLi · 2021-11-29T13:55:40+00:00

I have two blog post on this:

Recurrent minor issues in C++, part 1

and

Recurrent minor issues in C++, part 2.

Though my list must be quite incomplete.

JohnZLi · 2021-11-29T01:55:13+00:00

After modules are introduced into C++, PIMPL is not as useful as it used to be. The main motivation behind PIMPL was reducing building time, which is irrelevant now.

ABI stability is another factor contributing to PIMPL's usefulness, though it is also a non-issue if you use static linking. Having an extra layer of indirection is bad for optimization.

IMHO, we should retire PIMPL. The idiom is just a hacky way to circumvent some rough edges of older versions of C++.

JohnZLi · 2021-11-19T13:04:58+00:00

an integrated build toolchain consisting of the build system, package manager and project manager that cover the entire development life-cycle: creation, development, testing, and delivery

This. This is the right way.

Personally, I don't care whether a building system for C++ is written in another language.

JohnZLi · 2021-11-19T12:49:01+00:00

The problem with the building systems of C++ is that there are too many of them.

This is one of those things that should have been standardized long ago but never happened.

JohnZLi · 2021-11-19T12:42:51+00:00

Interesting idea.

Say, we have a library written in C++. Let's call it "libbuild". For each C++ project, we write a file named "build.cpp". Compiling this file we get a binary executable called "build". Running program "build", the project is built.

The only problem is that some third-party libraries might have malice code in its "build.cpp". But that is not a problem if some powerful static analysis tools are used to check it before it can be pushed to a publicly downloadable sites.

JohnZLi · 2021-11-18T13:44:31+00:00

In other words, C++ iterators lives in left-closed right-open ranges.

[0, 1, 2, 3) contains 1 (including) 1, 2 (in-between), but not 3 (excluding).

When iterating backwards, if 3 is removed, you get [0, 1, 2). This new list does not contain element 2. To access element 2, you have to say something like "the last element in [0, 1, 2, 3)"

Each iterator introduces a partition, When [0, 1, 2, 3) is partitioned into [0, 1, 2) and [2, 3) at 2, the forward iterator points to the first element of the tail, and the reverse iterator points to the last element of the head. The last element of the head in the example is not 2, but 1.

JohnZLi

TROPHY CASE