[Bug c++/57724] New: wrong error: returning a value from a constructor

[Bug c++/57724] New: wrong error: returning a value from a constructor

[joerg.richter@pdv-fs.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57724

            Bug ID: 57724
           Summary: wrong error: returning a value from a constructor
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: joerg.richter@pdv-fs.de

cat > t.cc <<EOF
void func();
struct A
{
    A()
    {
      return func();
    }
};
EOF
gcc t.cc


Produces:

t.cc: In constructor 'A::A()':
t.cc:6:19: error: returning a value from a constructor

I think this should work. (At least clang accepts it.)

[Bug c++/57724] wrong error: returning a value from a constructor

[fanael4 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57724

Fanael <fanael4 at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fanael4 at gmail dot com

--- Comment #1 from Fanael <fanael4 at gmail dot com> ---
12.1/12 (C++03) and 12.1/9 (C++11) state:

> A return statement in the body of a constructor shall not specify a return value.

It's a bug in Clang, not in GCC.

[Bug c++/57724] wrong error: returning a value from a constructor

[joerg.richter@pdv-fs.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57724

--- Comment #2 from Jörg Richter <joerg.richter@pdv-fs.de> ---
You mean the special case for 'void' does not apply in this case?
What a pity.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW724

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I'm inclined to say this is a Clang bug too.

[stmt.return]/3 "A return statement with an expression of type void can be used
only in functions with a return type of cv void;" and constructors do not have
any return type, not even void.

[class.ctor]/8 "A return statement in the body of a constructor shall not
specify a return value."  That doesn't really help, because a return statement
with an expression of type void does not return a value.

[Bug c++/57724] wrong error: returning a value from a constructor

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57724

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #4 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Basing on the analysis provided by Jon + the most recent ICC also rejects the
snippet, I think we can safely close the bug.

[Bug c++/57724] wrong error: returning a value from a constructor

[joerg.richter@pdv-fs.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57724

--- Comment #5 from Jörg Richter <joerg.richter@pdv-fs.de> ---
BTW: There is currently a discussion [1] on this topic on the 
"ISO C++ Standard - Discussion" list.

[1]
https://groups.google.com/a/isocpp.org/d/msg/std-discussion/ehqGBMsswjk/nbsubYASnPgJ
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Subject: [Bug tree-optimization/57723] Missed optimization: recursion around empty function
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW723

--- Comment #7 from petschy at gmail dot com ---
Is it a plausible assumption that if a function is not marked as 'noreturn' and
the loop doesn't change the program's state then the loop could be optimized
away?

Cases:
- the loop terminates, but the state is not changed, NOP
- the loop does not terminate (in this case a cycle of the Node's), but the
function should return (no noreturn attr), so this is probably a bug in the prg

I can't think of any cases right now for the second point where that would be
the desired behaviour of the program, instead of a bug. Please comment on this.