[Bug c++/85691] Faulty Class Member Default Initialization - No Warning or Error

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85691

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

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

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Did you forget to enable warnings? GCC warns about test2 but not test:

$ g++ -Wall -c 85691.cc
85691.cc: In constructor ‘test2::test2(int)’:
85691.cc:14:13: warning: ‘test2::data’ will be initialized after [-Wreorder]
         int data;
             ^~~~
85691.cc:13:13: warning:   ‘int test2::x’ [-Wreorder]
         int x;
             ^
85691.cc:16:9: warning:   when initialized here [-Wreorder]
         test2(int o) : data(o), x(data) { }
         ^~~~~


Clang has the same behaviour for -Wreorder, but it additionally warns about
test::data with -Wuninitialized:

85691.cc:4:17: warning: field 'data' is uninitialized when used here
[-Wuninitialized]
        int x = data;
                ^
85691.cc:7:9: note: during field initialization in this constructor
        test(int o) : data(o) { }
        ^
85691.cc:16:24: warning: field 'data' will be initialized after field 'x'
[-Wreorder]
        test2(int o) : data(o), x(data) { }
                       ^
85691.cc:16:35: warning: field 'data' is uninitialized when used here
[-Wuninitialized]
        test2(int o) : data(o), x(data) { }
                                  ^
3 warnings generated.

We already have Bug 19808 covering this.

*** This bug has been marked as a duplicate of bug 19808 ***