[Bug c++/21951] New: [gcc-4.0 regression, rejects-valid] std::vector.reserve() unusable with -Werror -Wall -O -fno-exceptions

["dank at kegel dot com" <gcc-bugzilla@gcc.gnu.org>]

Compiling the following code:

#include <vector>
std::vector<int> *factory()
{
        std::vector<int> *p = new std::vector<int>;
        p->reserve(10);
        return p;
}

with -Wall -O -fno-exceptions yields the following error in gcc-4.0.0
and gcc-4.0-20050602:

.../include/c++/4.0.0/bits/vector.tcc: In member function 'void std::vector<_Tp,
_Alloc>::reserve(size_t) [with _Tp = int, _Alloc = std::allocator<int>]':
.../include/c++/4.0.0/bits/vector.tcc:78: warning: control may reach end of
non-void function 'typename _Alloc::pointer std::vector<_Tp,
_Alloc>::_M_allocate_and_copy(size_t, _ForwardIterator, _ForwardIterator) [with
_ForwardIterator = int*, _Tp = int, _Alloc = std::allocator<int>]' being inlined

The warning comes from a catch/rethrow block deep in the bowels of stl
which (because of -fno-exceptions) evaluates to if(false).

This is a false positive warning, which would be fine except
for shops whose policy is to always compile with -Werror -Wall;
there, the warning is fatal.  And because this problem is not
confined to just one user source file, it's hard to work around.

This problem does not occur in gcc-3.4.3 nor in recent gcc-4.1 snapshots.

cf. discussion here: http://gcc.gnu.org/ml/libstdc++/2005-06/msg00073.html

-- 
           Summary: [gcc-4.0 regression, rejects-valid]
                    std::vector.reserve() unusable with -Werror -Wall -O -
                    fno-exceptions
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: dank at kegel dot com
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21951