[Bug libstdc++/31638] New: [4.0/4.1/4.2/4.3 Regression] string usage leads to warning with -Wcast-align

["tbm at cyrius dot com" <gcc-bugzilla at gcc dot gnu dot org>]

[ Forwarded from http://bugs.debian.org/382153  This issue has been reported
by Margarita Manterola who also provided the testcase ]

If you compile the following testcase with -Wcast-align  you get a warning
on certain architectures, including alpha, arm, hppa, ia64 and sparc.
I've verified this on ia64 with gcc 4.0, 4.1 and 4.3.  3.3 and 3.4 don't
show this warning. The warning goes away when you include <iostream> in
addition to <string>.


tbm@coconut0:~/src$ /usr/lib/gcc-snapshot/bin/g++ -Wcast-align x.c
/usr/lib/gcc-snapshot/lib/gcc/ia64-linux-gnu/4.3.0/../../../../include/c++/4.3.0/bits/basic_string.h:
In member function 'std::basic_string<_CharT, _Traits, _Alloc>::_Rep*
std::basic_string<_CharT, _Traits, _Alloc>::_M_rep() const [with _CharT = char,
_Traits = std::char_traits<char>, _Alloc = std::allocator<char>]':
/usr/lib/gcc-snapshot/lib/gcc/ia64-linux-gnu/4.3.0/../../../../include/c++/4.3.0/bits/basic_string.h:496:
  instantiated from 'std::basic_string<_CharT, _Traits,
_Alloc>::~basic_string() [with _CharT = char, _Traits = std::char_traits<char>,
_Alloc = std::allocator<char>]'
x.c:6:   instantiated from here
/usr/lib/gcc-snapshot/lib/gcc/ia64-linux-gnu/4.3.0/../../../../include/c++/4.3.0/bits/basic_string.h:288:
warning: cast from 'char*' to 'std::basic_string<char, std::char_traits<char>,
std::allocator<char> >::_Rep*' increases required alignment of target type

Testcase:

#include <string>

using namespace std;

int main (int argc, char **argv) {
        string hi;
        hi = "Hi";
        return 0;
}


-- 
           Summary: [4.0/4.1/4.2/4.3 Regression] string usage leads to
                    warning with -Wcast-align
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tbm at cyrius dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31638