[Bug c++/42121] New: g++ should warn or error on internal 0 size array in struct

[david dot resnick at comverse dot com]

Currently g++ requires the -pedantic flag to give a warning on a zero sized
array that is not the last field in a struct.  As far as I can see, this is
actually always a significant error if it is not the trailing field in the
struct...

Demonstration:
temp(510)$ cat zero-size-array.cpp
#include <iostream>
#include <cstddef>

struct bogus
{
    int a;
    char b[];
    int c;

} bogus;

int main(void)
{
    std::cout << "size of struct bogus =" << sizeof(bogus) << std::endl;
    std::cout << "offset of field b =" << offsetof(struct bogus, b) <<
std::endl;
    std::cout << "offset of field c =" << offsetof(struct bogus, b) <<
std::endl;
    return 0;
}
temp(511)$ g++ -Wall -o zero-size-array
zero-size-array.cppsize-array.cppe-array.cpp
temp(512)$ zero-size-array        
size of struct bogus =8
offset of field b =4
offset of field c =4
temp(513)$ g++ -Wall  -pedantic -o zero-size-array
zero-size-array.cppize-array.cpp
zero-size-array.cpp:7: error: ISO C++ forbids zero-size array 'b'
temp(514)$ g++ --version
g++ (GCC) 4.1.2 20070626 (Red Hat 4.1.2-14)

-David


-- 
           Summary: g++ should warn or error on internal 0 size array in
                    struct
           Product: gcc
           Version: 4.1.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: david dot resnick at comverse dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42121