Destructors are vastly superior to the finally keyword because they only require us to remember a single time to release resources (in the destructor) as opposed to every finally clause. For example, a file always closes itself when it goes out of scope instead of having to be explicitly closed by the person who opened the file. Syntax is also less cluttered with less indentation, especially when multiple objects are created that require nested try... finally blocks. Not to mention how branching and conditional initialization complicates things. You can often pair up constructors with destructors in the code so that it becomes very obvious when resource acquisition and release do not match up.
C++ says “We have try... finally at home”
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Re: C++ says “We have try... finally at home”
#22Destructors are vastly superior to the finally keyword because they only require us to remember a single time to release resources (in the destructor) as opposed to every finally clause. For example, a file always closes itself when it goes out of scope instead of having to be explicitly closed by the person who opened the file. Syntax is also less cluttered with less indentation, especially when multiple objects are…
Destructors and finally clauses serve different purposes IMO. Most of the languages that have finally clauses also have destructors.
> Syntax is also less cluttered with less indentation, especially when multiple objects are created that require nested try... finally blocks.
I think that's more of a point against try...catch/maybe exceptions as a whole, rather than the finally block. (Though I do agree with that. I dislike that aspect of exceptions, and generally prefer something closer to std::expected or Rust Result.)
Re: C++ says “We have try... finally at home”
#23The submitted title is missing the salient keyword "finally" that motivates the blog post. The actual subtitle Raymond Chen wrote is: "C++ says “We have try…finally at home.”" It's a snowclone based on the meme, "Mom, can we get ? No, we have at home." : https://www.google.com/search?q=%22we+have+x+at+home%22+meme In other words, Raymond is saying... "We already have Java feature of 'finally' at home in the C++ refri…
HN has some heuristics to reduce hyperbole in submissions which occasionally backfire amusingly.
You have a few minutes to change the title after the submission, I do it all the time.
Re: C++ says “We have try... finally at home”
#24Destructors are vastly superior to the finally keyword because they only require us to remember a single time to release resources (in the destructor) as opposed to every finally clause. For example, a file always closes itself when it goes out of scope instead of having to be explicitly closed by the person who opened the file. Syntax is also less cluttered with less indentation, especially when multiple objects are…
A writable file closing itself when it goes out of scope is usually not great, since errors can occur when closing the file, especially when using networked file systems.
Re: C++ says “We have try... finally at home”
#25Destructors are vastly superior to the finally keyword because they only require us to remember a single time to release resources (in the destructor) as opposed to every finally clause. For example, a file always closes itself when it goes out of scope instead of having to be explicitly closed by the person who opened the file. Syntax is also less cluttered with less indentation, especially when multiple objects are…
Destructors and finally clauses serve different purposes IMO. Most of the languages that have finally clauses also have destructors. > Syntax is also less cluttered with less indentation, especially when multiple objects are created that require nested try... finally blocks. I think that's more of a point against try...catch/maybe exceptions as a whole, rather than the finally block. (Though I do agree with that. I d…
> Most of the languages that have finally clauses also have destructors.
Hm, is that true? I know of finally from Java, JavaScript, C# and Python, and none of them have proper destructors. I mean some of them have object finalizers which can be used to clean up resources whenever the garbage collector comes around to collect the object, but those are not remotely similar to destructors which typically run deterministically at the end of a scope. Python's 'with' syntax comes to mind, but that's very different from C++ and Rust style destructors since you have to explicitly ask the language to clean up resources with special syntax.
Which languages am I missing which have both try..finally and destructors?
Re: C++ says “We have try... finally at home”
#26Earlier quoted context omitted.
HN has some heuristics to reduce hyperbole in submissions which occasionally backfire amusingly.
Yeah it's a huge mistake IMO. I see it fucking up titles so frequently, and it flies in the face of the "do not editorialise titles" rule: [...] please use the original title, unless it is misleading or linkbait; don't editorialize. It is much worse, I think, to regularly drastically change the meaning of a title automatically until a moderator happens to notice to change it back, than to allow the occasional somewha…
Personally, I would rather we have a lower bar for killing submissions quickly with maybe five or ten flags and less automated editorializing of titles.
Re: C++ says “We have try... finally at home”
#27Destructors are vastly superior to the finally keyword because they only require us to remember a single time to release resources (in the destructor) as opposed to every finally clause. For example, a file always closes itself when it goes out of scope instead of having to be explicitly closed by the person who opened the file. Syntax is also less cluttered with less indentation, especially when multiple objects are…
Python has that too, it's called a context manager, basically the same thing as C++ RAII.
You can argue that RAII is more elegant, because it doesn't add one mandatory indentation level.
Re: C++ says “We have try... finally at home”
#28Earlier quoted context omitted.
"using namespace std;" goes a long way to make C++ more readable and I don't really care about the potential issues. But yeah, due to a lack of a nice module system, this will quickly cause problems with headers that unload everything into the global namespace, like the windows API. I wish we had something like Javascript's "import {vector, string, unordered_map} from std;". One separate using statement per item is a…
Standard library modules: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p24... I have thoroughly forgotten which header std::ranges::iota comes from. I don't care either.
Last time I tried, modules were a spuriously supported mess. I'll give them another try once they have ironclad support in cmake, gcc, clang and Visual Studio.
Re: C++ says “We have try... finally at home”
#29Earlier quoted context omitted.
#include #define RemParens_(VA) RemParens__(VA) #define RemParens__(VA) RemParens___ VA #define RemParens___(...) __VA_ARGS__ #define DoConcat_(A,B) DoConcat__(A,B) #define DoConcat__(A,B) A##B #define defer(BODY) struct DoConcat_(Defer,__LINE__) { ~DoConcat_(Defer,__LINE__)() { RemParens_(BODY) } } DoConcat_(_deferrer,__LINE__) int main() { { defer(( std::cout
Why would that be preferable to just using an RAII style scope_exit with a lambda
Meh, I was going to use the preprocessor for __LINE__ anyways (to avoid requiring a variable name) so I just made it an "old school lambda." Besides, scope_exit is in C++23 which is still opt-in in most cases.
Re: C++ says “We have try... finally at home”
#30I like how Swift solved this: there's a more universal `defer { ... }` block that's executed at the end of a given scope no matter what, and after the `return` statement is evaluated if it's a function scope. As such it has multiple uses, not just for `try ... finally`.
I was contemplating what it would look like to provide this with a macro in Rust, and of course someone has already done it. It's syntactic sugar for the destructor/RAII approach. https://docs.rs/defer-rs/latest/defer_rs/
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