[Bug c++/66161] New: gcc silent about type incompleteness in error message

[Bug c++/66161] New: gcc silent about type incompleteness in error message

[tromey at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66161

            Bug ID: 66161
           Summary: gcc silent about type incompleteness in error message
           Product: gcc
           Version: 4.9.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tromey at gcc dot gnu.org
  Target Milestone: ---

This source is distilled from a more complicated real-world
case that arose in https://bugzilla.mozilla.org/show_bug.cgi?id=1165184

class Base { };

class Incomplete; // : public Base

template<typename T>
Base* blah_cast(T *arg) { return arg; }

Base* function(Incomplete *arg)
{
  return blah_cast(arg);
}


Compiling this yields:

pokyo. g++ -c s.cc
s.cc: In instantiation of ‘Base* blah_cast(T*) [with T = Incomplete]’:
s.cc:10:23:   required from here
s.cc:6:34: error: cannot convert ‘Incomplete*’ to ‘Base*’ in return
 Base* blah_cast(T *arg) { return arg; }
                                  ^


In this case it is obvious that Incomplete is an incomplete type.
However, in the real-world code this is far from obvious.

I think it would be handy if gcc printed something like
"note: type 'Incomplete' is incomplete at this point; missing include?".
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Subject: [Bug target/66136] AArch64 geniterators.sh relies on GNU sed syntax, causing build failure on FreeBSD and probably Mac
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idf136

Richard Earnshaw <rearnsha at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-05-15
     Ever confirmed|0                           |1

--- Comment #4 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
According to:

http://pubs.opengroup.org/onlinepubs/009695399/utilities/sed.html

[In a replacement] the meaning of a '\' immediately followed by any character
other than '&', '\', a digit, or the delimiter character used for this command,
is unspecified.

So I think that rules out all the normal escaped characters.

[Bug c++/66161] gcc silent about type incompleteness in error message

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66161

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE
   Target Milestone|---                         |5.0

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is fixed in 5.1

*** This bug has been marked as a duplicate of bug 13981 ***