3 ms·

The constructor error problem is easily solved by using factory functions and two phase construction. The problem is that the standard library is relying on exc

by jupp0r 3y ago

The constructor error problem is easily solved by using factory functions and two phase construction. The problem is that the standard library is relying on exceptions quite a bit and major parts become unusable.

lelanthran 3y ago
For what definition of "easy"? Simply passing by value can result in a constructor that fails, while still bypassing any of the factory functions.
- jupp0r 3y ago
  Easy as in "competent C++ programmers do this every day"? If the copy constructor can fail and you don't want that, then delete it?
  - lelanthran 3y ago
    > If the copy constructor can fail and you don't want that, then delete it? You're trivialising just how deeply embedded exceptions are into the design of the language. I gave just one example and it was not meant to be exhaustive, just one 'gotcha' that you won't find out till runtime and your program starts (worst case) giving you slightly incorrect results without you knowing about it... So, yeah, if you want to do without exceptions (without having your program execute random code) you need to know in advance what special cases to handle, like unintended copy construction, or failures in overloaded operators, or which std libs can be used and which cannot, or which C++ libraries can be linked, and which cannot. All of which is perfectly possible, but taken together is hardly "easy". It's tedious, error-prone, bloated ... but hardly what someone would call "easy".
    - jupp0r 3y ago
      C++ is complicated, I get it. Things that are "easy" in other languages are "hard" in C++. That doesn't mean that writing C++ code that can't throw isn't something that tens of thousands of engineers are doing every day. One could argue that all of C++ is tedious, bloated and error-prone.
- kwant_kiddo 3y ago
  it is easy? It is the named constructor idiom. I don't understand why jupp0r is getting downvoted? Most big public c++ projects turn off exceptions, so it seems to be the norm more than anything.
  - gpderetta 3y ago
    Because two phase construction is a widely disliked idiom. Named constructors retuning optional objects are tolerable though.
    - jupp0r 3y ago
      Two phase construction isn't widely disliked, it's completely fine if it's used as an implementation detail of a factory.
  - pjmlp 3y ago
    Only the big public C++ projects that blindly follow Google's style guide, mostly.
    - kwant_kiddo 3y ago
      I don't think this is true, but I don't know this for sure. From what I have read it seems that 'only' Bloomberg, Meta and Microsoft that uses c++ with exceptions. And since both microsoft and meta are adopting rust in their services it seems to me that they are looking for another language than C++. (why else adopt a new language?) Following seems not to use exceptions(?) LLVM: https://llvm.org/docs/CodingStandards.html#do-not-use-rtti-or-exceptions https://llvm.org/docs/CodingStandards.html#do-not-use-rtti-o... AWS: (seems to be using Google's guidelines to be fair) Webkit: https://gist.github.com/derofim/df604f2bf65a506223464e3ffd96a78a https://gist.github.com/derofim/df604f2bf65a506223464e3ffd96... Qt: https://doc.qt.io/qt-6/exceptionsafety.html https://doc.qt.io/qt-6/exceptionsafety.html gcc: https://gcc.gnu.org/codingconventions.html#Exceptions https://gcc.gnu.org/codingconventions.html#Exceptions Unreal: (not totally sure, but I think it uses error codes internally) Most of the embedded world. + any console game you ever played or heard of.

by jupp0r 3y ago

lelanthran 3y ago

For what definition of "easy"? Simply passing by value can result in a constructor that fails, while still bypassing any of the factory functions.

jupp0r 3y ago
Easy as in "competent C++ programmers do this every day"? If the copy constructor can fail and you don't want that, then delete it?
- lelanthran 3y ago
  > If the copy constructor can fail and you don't want that, then delete it? You're trivialising just how deeply embedded exceptions are into the design of the language. I gave just one example and it was not meant to be exhaustive, just one 'gotcha' that you won't find out till runtime and your program starts (worst case) giving you slightly incorrect results without you knowing about it... So, yeah, if you want to do without exceptions (without having your program execute random code) you need to know in advance what special cases to handle, like unintended copy construction, or failures in overloaded operators, or which std libs can be used and which cannot, or which C++ libraries can be linked, and which cannot. All of which is perfectly possible, but taken together is hardly "easy". It's tedious, error-prone, bloated ... but hardly what someone would call "easy".
  - jupp0r 3y ago
    C++ is complicated, I get it. Things that are "easy" in other languages are "hard" in C++. That doesn't mean that writing C++ code that can't throw isn't something that tens of thousands of engineers are doing every day. One could argue that all of C++ is tedious, bloated and error-prone.
kwant_kiddo 3y ago
it is easy? It is the named constructor idiom. I don't understand why jupp0r is getting downvoted? Most big public c++ projects turn off exceptions, so it seems to be the norm more than anything.
- gpderetta 3y ago
  Because two phase construction is a widely disliked idiom. Named constructors retuning optional objects are tolerable though.
  - jupp0r 3y ago
    Two phase construction isn't widely disliked, it's completely fine if it's used as an implementation detail of a factory.
- pjmlp 3y ago
  Only the big public C++ projects that blindly follow Google's style guide, mostly.
  - kwant_kiddo 3y ago
    I don't think this is true, but I don't know this for sure. From what I have read it seems that 'only' Bloomberg, Meta and Microsoft that uses c++ with exceptions. And since both microsoft and meta are adopting rust in their services it seems to me that they are looking for another language than C++. (why else adopt a new language?) Following seems not to use exceptions(?) LLVM: https://llvm.org/docs/CodingStandards.html#do-not-use-rtti-or-exceptions https://llvm.org/docs/CodingStandards.html#do-not-use-rtti-o... AWS: (seems to be using Google's guidelines to be fair) Webkit: https://gist.github.com/derofim/df604f2bf65a506223464e3ffd96a78a https://gist.github.com/derofim/df604f2bf65a506223464e3ffd96... Qt: https://doc.qt.io/qt-6/exceptionsafety.html https://doc.qt.io/qt-6/exceptionsafety.html gcc: https://gcc.gnu.org/codingconventions.html#Exceptions https://gcc.gnu.org/codingconventions.html#Exceptions Unreal: (not totally sure, but I think it uses error codes internally) Most of the embedded world. + any console game you ever played or heard of.