c++/7023: C++ structure initialization problem if too few initializers given

c++/7023: C++ structure initialization problem if too few initializers given

[Gary.Jenkins]

>Number:         7023
>Category:       c++
>Synopsis:       C++ structure initialization problem if too few initializers given
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Jun 13 12:36:06 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     Gary Jenkins
>Release:        egcs-2.91.60
>Organization:
>Environment:
SunOS sunbc6148 5.6 Generic_105181-23 sun4u sparc SUNW,Ultra-5_10
>Description:
Problem:
    Structure initialization doesn't seem to work correctly if you get too
    few initializers.

Expected Behavior:
    If too few initializers are given, unspecified structure members
    should be initialized with zero.

Example:
    struct Foo
    {
        const int a;
        const int b;
    };

    Foo f = { 0 };  // should initilize f.a and f.b to zero
Reference:

    C Language
    ----------
    "The ANSI C Programming Language (Second Edition)" , Copyright 1988 by AT&T
    Brian W. Kerninghan, Dennis M. Ritchie,

    Page 219, section A8.7 "Initialization":
        "If there are fewer initializers in the list then members of the structure,
         the trailing members are initialized with 0".


    C++ Language
    ------------
    This is alluded to but not stated as clearly in the C++ bible:

    "The C++ Programming Language (Special Edition", Copyright 2000 by AT&T
    Bjarne Stroustrup  

    Page 89, section 5.2.1 "Array Initializers":
    "If the initializer supplies too few elements, 0 is assumed for the 
     remaining array elements".

    Page 102, section 5.7 "Structures"
    "The notation used for initializing arrays can also be used for initializing
     variables of structure types".
>How-To-Repeat:
File main.cc:
struct Foo
{
    const int a;
    const int b;
};

int main()
{
    Foo f = { 0 };              // error: uninitialized const member `b'

    return 0;
}


Compile main.cc:

    > g++ main.cc
    main.cc: In function `int main()':
    main.cc:9: uninitialized const member `b'
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
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Re: c++/7023: C++ structure initialization problem if too few initializers given

[nathan]

Synopsis: C++ structure initialization problem if too few initializers given

State-Changed-From-To: open->closed
State-Changed-By: nathan
State-Changed-When: Sat Sep 14 14:50:15 2002
State-Changed-Why:
    not a bug. [8.5.1]/7 -> [8.5]/9 -> ill formed

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=7023