function declaration

Mac1ek · 01-31-2024, 03:47 PM

is any differences for declare function:

Code:

int foo(int) {
   //...
   return (0);
}

with most modern style:

Code:

auto foo(int) -> int {
   //...
   return (0);
}

And the same about main:

Code:

auto main(int argc, char* argv[]) -> int {
   //...
   return (0);
}

Thanks for answer.

dugan · 01-31-2024, 03:57 PM

No difference.

The trailing return type style is actually needed for:

A) lambdas

B) template functions where the return type depends on the types of the arguments

NevemTeve · 01-31-2024, 04:00 PM

Tried the second one, with gcc-13.2, with the newest -std=c2x setting, but it doesn't compile.

Code:

$ gcc -std=c2x Mac1ek.c
Mac1ek.c:1:1: error: ‘auto’ requires a plain identifier, possibly with attributes, as declarator
    1 | auto foo(int) -> int {

GazL · 01-31-2024, 05:03 PM

Doesn't the int argument need a name?

dugan · 01-31-2024, 06:15 PM

This compiles fine for me:

Code:

❯ cat auto.cpp
auto main() -> int
{
    return 0;
}
                                                                            
❯ g++ --std=c++23 auto.cpp

EdGr · 01-31-2024, 07:12 PM

NevemTeve - The file needs a .cpp extension.

I wish the C++ standards committee would pick a different name for their new language.
Ed

dugan · 01-31-2024, 07:47 PM

Quote:

Originally Posted by EdGr

NevemTeve - The file needs a .cpp extension.

And he should be building with g++, not gcc.

rclark · 01-31-2024, 08:05 PM

I'll stick to the following form myself unless for some reason I 'need' to use the 'auto' and -> . Keep It Simple (and readable) ...

Code:

int foo(int aVar) 
   {
   //... do something
   return(0);
   }

NevemTeve · 01-31-2024, 11:22 PM

Quote:

Originally Posted by EdGr

The file needs a .cpp extension.

That's a piece of information which could have been added into the Original Post. (Note: file extension .cc means the same and it saves a byte.)

dugan · 02-01-2024, 08:43 AM

If you want to save two bytes, you can use .C (big C)

GazL · 02-01-2024, 09:06 AM

Quote:

Originally Posted by dugan

If you want to save two bytes, you can use .C (big C)

.C is no good on a case-insensitive filesystem. I've always used .cc (not that I write much c++).

bigearsbilly · 02-02-2024, 08:25 AM

Quote:

Originally Posted by EdGr

NevemTeve - The file needs a .cpp extension.

I wish the C++ standards committee would pick a different name for their new language.
Ed

hear! hear!

sundialsvcs · 02-02-2024, 08:36 PM

I agree: “it’s different but not better.” No one is ever going to rewrite billions of lines of existing, working, source code.

Of course I am familiar with these idioms from other languages, but that’s what they called them from the start. Is it really worth it to add all this “new syntax” to what you’re still calling, “C++?” Frankly, I don’t think so. I see no “ROI.”

NevemTeve · 02-06-2024, 07:07 AM

An actual example: an older g++ 4.8.2 couldn't compile this piece from harfbuzz-8.3 (src/hb-serialize.hh line 158):

Code:

auto all_links () const -> 
  decltype ((( hb_concat (this->real_links, this->virtual_links) )))
  { return (( hb_concat (this->real_links, this->virtual_links) )); }

but could compile it in this rewritten format:

Code:

    hb_vector_t<link_t> all_links ()
        { return hb_concat (this->real_links, this->virtual_links); }

Obviously, the first one is better, as it is much harder to understand. Mind you, this is the output of the preprocessing, the original is like this:
before:

Code:

auto all_links () const HB_AUTO_RETURN
        (( hb_concat (this->real_links, this->virtual_links) ));

after:

Code:

hb_vector_t<link_t> all_links ()
        { return hb_concat (this->real_links, this->virtual_links); }