libstdc++: Make istreambuf_iterator base class consistent (PR92285)
authorJonathan Wakely <jwakely@redhat.com>
Fri, 10 Jan 2020 15:27:39 +0000 (15:27 +0000)
committerJonathan Wakely <redi@gcc.gnu.org>
Fri, 10 Jan 2020 15:27:39 +0000 (15:27 +0000)
commit7918cb93f6f752cec468f107eb944dc0da61ec6b
treec28d83e2ee9e985e1032aeb5deeeae5013195255
parentd5c23c6ceacf666f218676b648801379044e326a
libstdc++: Make istreambuf_iterator base class consistent (PR92285)

Since LWG 445 was implemented for GCC 4.7, the std::iterator base class
of std::istreambuf_iterator changes type depending on the -std mode
used. This creates an ABI incompatibility between different -std modes.

This change ensures the base class always has the same type. This makes
layout for C++98 compatible with the current -std=gnu++14 default, but
no longer compatible with C++98 code from previous releases. In practice
this is unlikely to cause real problems, because it only affects the
layout of types with two std::iterator base classes, one of which comes
from std::istreambuf_iterator. Such types are expected to be vanishingly
rare.

PR libstdc++/92285
* include/bits/streambuf_iterator.h (istreambuf_iterator): Make type
of base class independent of __cplusplus value.
[__cplusplus < 201103L] (istreambuf_iterator::reference): Override the
type defined in the base class
* testsuite/24_iterators/istreambuf_iterator/92285.cc: New test.
* testsuite/24_iterators/istreambuf_iterator/requirements/
base_classes.cc: Adjust expected base class for C++98.

From-SVN: r280116
libstdc++-v3/ChangeLog
libstdc++-v3/include/bits/streambuf_iterator.h
libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/92285.cc [new file with mode: 0644]
libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/requirements/base_classes.cc