[LLVMbugs] [Bug 17413] New: Missing item referenced in compiler error.

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17413

            Bug ID: 17413
           Summary: Missing item referenced in compiler error.
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: gmisocpp at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Compile the following program with g++ and clang++ and compare the resulting
output from each compiler. Compiler instructions and output follow this
program.
Note in the output that g++ seems to have a superior error message.

#include <cstdio>
using namespace std;

class my_object {
public:
    int id_;
    my_object() { }
    my_object(int id) : id_(id) 
    {
        printf( "constructed my_object %d\n", id_ );
    }
    ~my_object()
    {
        printf( "destructed my_object\n" );
    }
    int get_id() { return id_; }
};
class X {
public:

private:
    union {
        char storage [sizeof(my_object)];
        my_object object;
    } y;
};

int main()
{
    X x;
}


g++ command line and output:

// libcxx references can be omitted in your tests.

c:\test>g++ -fno-exceptions -static -std=c++11 -Wall moslow2.cpp
-I/libcxx/include -L/libcxx_build/lib -lc++ -omo2.exe
moslow2.cpp: In function 'int main()':
moslow2.cpp:30:7: error: use of deleted function 'X::X()'
     X x;
       ^
moslow2.cpp:18:7: note: 'X::X()' is implicitly deleted because the default
definition would be ill-formed:
 class X {
       ^
moslow2.cpp:18:7: error: use of deleted function 'X::<anonymous
union>::<constructor>()'
moslow2.cpp:22:11: note: 'X::<anonymous union>::<constructor>()' is implicitly
deleted because the default definition woul
d be ill-formed:
     union {
           ^
moslow2.cpp:24:19: error: union member 'X::<anonymous union>::object' with
non-trivial 'my_object::my_object()'
         my_object object;
                   ^
moslow2.cpp:18:7: error: use of deleted function 'X::<anonymous
union>::~<constructor>()'
 class X {
       ^
moslow2.cpp:22:11: note: 'X::<anonymous union>::~<constructor>()' is implicitly
deleted because the default definition wou
ld be ill-formed:
     union {
           ^
moslow2.cpp:24:19: error: union member 'X::<anonymous union>::object' with
non-trivial 'my_object::~my_object()'
         my_object object;
                   ^
moslow2.cpp:30:7: error: use of deleted function 'X::~X()'
     X x;
       ^
moslow2.cpp:18:7: note: 'X::~X()' is implicitly deleted because the default
definition would be ill-formed:
 class X {
       ^
moslow2.cpp:18:7: error: use of deleted function 'X::<anonymous
union>::~<constructor>()'

c:\test>
Clang compile land and output:

c:\test>clang++ -fno-exceptions -static -std=c++11 -Wall moslow2.cpp
-I/libcxx/include -L/libcxx_build/lib -lc++ -omo2.exe

moslow2.cpp:30:7: error: call to implicitly-deleted default constructor of 'X'
    X x;
      ^
moslow2.cpp:25:7: note: default constructor of 'X' is implicitly deleted
because field 'y' has a deleted default
      constructor
    } y;
      ^
moslow2.cpp:24:19: note: default constructor of '' is implicitly deleted
because variant field 'object' has a non-trivial
      default constructor
        my_object object;
                  ^
1 error generated.

*** I find the g++ error has more clarity then the clang++ error. Note that
clang++ seems to use '' to specify anonymous but it looks like a mistake. 

Suggestion, remove use if '' and get nearer to the g++ error.

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