[Bug c++/21917] Missing warning?

[Bug c++/21917] Missing warning?

[gdr at gcc dot gnu dot org]

------- Comment #3 from gdr at gcc dot gnu dot org  2005-11-24 02:25 -------
(In reply to comment #2)
> This is how C++ is done, maybe a warning can be emitted but it seems like it
> will emitt too much for 
> valid C++ code.
> 

I don't know; the code shown is very contrived to my taste.


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gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-11-24 02:25:02
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning?

[manu at gcc dot gnu dot org]

------- Comment #4 from manu at gcc dot gnu dot org  2007-01-09 15:02 -------
Have you tried compiling with -pedantic -Wall -Wextra ?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning?

[igodard at pacbell dot net]

------- Comment #5 from igodard at pacbell dot net  2007-01-09 16:36 -------
No message on 4.1.1 despite -pedantic -Wall -Wextra


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning when trying to explicitly construct a virtual base

[manu at gcc dot gnu dot org]

------- Comment #6 from manu at gcc dot gnu dot org  2007-01-20 16:52 -------
Not sure if the summary is 100% correct but it is far better than the previous
one.


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manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Missing warning?            |Missing warning when trying
                   |                            |to explicitly construct a
                   |                            |virtual base


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning when trying to explicitly construct a virtual base

[r_q_einstein-gccgnuorg at yahoo dot com]

------- Comment #7 from r_q_einstein-gccgnuorg at yahoo dot com  2008-06-05 23:07 -------
I've run across this, too.
I agree with Ivan's 2005-06-04 suggestion.
It would be nice if the compiler would emit a warning that the derived class's
constructor's call to the virtual base class's non-default constructor is being
ignored and overridden by an implicit call to the virtual base class's default
constructor.
Similarly, if the virtual base class fails to specify a default constructor
(and specifies only a non-default one), the derived class's constructor's call
to the virtual base class's non-default constructor produces only this error
message:

In constructor 'top::top()':
 error: no matching function for call to 'virt::virt()'

which leaves the developer scratching his/her head if he doesn't know that the
C++ spec. requires virtual base classes to have default constructors.  (True,
s/he should know, but the compile error message could be more helpful.)
Something to the effect of:
"virtual base class lacks default constructor" would be much more helpful.

If this issue is different enough to warrant a separate "bug" report, let me
know and I'll be happy to file it separately.
Thanks.


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r_q_einstein-gccgnuorg at yahoo dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |r_q_einstein-gccgnuorg at
                   |                            |yahoo dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] New: Missing warning? (or error?)

[igodard at pacbell dot net]

struct  virt { virt() : i(2) {} virt(int i) : i(i){} int i;  };
struct der1 : public virtual virt { der1(int i) : virt(i) {} };
struct der2 : public virtual virt { der2(int i) : virt(i) {} };
struct top : public der1, public der2 {
    top () : der1(0), der2(1) {} };
int main() { top t; }


Compiles without comment. However, the null constructor for "virt" is called
rather than the explicit constructor that is indicated by the constructor chain
from top. In fact, the der* constructors say " : virt(i)" but that
sub-constructor will never be called because virt is a virtual base class.

I don't know if it is actually an error to try to explicitly construct a virtual
base, but is sure is misleading and I think deserves at least a warning.

-- 
           Summary: Missing warning? (or error?)
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: igodard at pacbell dot net
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning?

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|Missing warning? (or error?)|Missing warning?


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning?

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|normal                      |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917

[Bug c++/21917] Missing warning?

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21917