Missing item referenced in compiler error.

[llvmbot]

Bugzilla Link	17413
Version	trunk
OS	Windows NT
Reporter	LLVM Bugzilla Contributor
CC	@efriedma-quic

Extended Description

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.

[efriedma-quic]

Err, wait, nevermind.

[efriedma-quic]

Trunk clang gives:

:24:19: error: union member 'object' has a non-trivial constructor my_object object; ^ :7:5: note: because type 'my_object' has a user-provided default constructor my_object() { } ^ 1 error generated.