[PATCH] Enforce allocator::value_type consistency for containers in C++2a

[Jonathan Wakely]

On 03/06/19 22:34 +0100, Jonathan Wakely wrote:
>On 03/06/19 23:17 +0200, Rainer Orth wrote:
>>Hi Jonathan,
>>
>>>In previous standards it is undefined for a container and its allocator
>>>to have a different value_type. Libstdc++ has traditionally allowed it
>>>as an extension, automatically rebinding the allocator to the
>>>container's value_type. Since GCC 8.1 that extension has been disabled
>>>for C++11 and later when __STRICT_ANSI__ is defined (i.e. for
>>>-std=c++11, -std=c++14, -std=c++17 and -std=c++2a).
>>>
>>>Since the acceptance of P1463R1 into the C++2a draft an incorrect
>>>allocator::value_type now requires a diagnostic. This patch implements
>>>that by enabling the static_assert for -std=gnu++2a as well.
>>>
>>>	* doc/xml/manual/status_cxx2020.xml: Document P1463R1 status.
>>>	* include/bits/forward_list.h [__cplusplus > 201703]: Enable
>>>	allocator::value_type assertion for C++2a.
>>>	* include/bits/hashtable.h: Likewise.
>>>	* include/bits/stl_deque.h: Likewise.
>>>	* include/bits/stl_list.h: Likewise.
>>>	* include/bits/stl_map.h: Likewise.
>>>	* include/bits/stl_multimap.h: Likewise.
>>>	* include/bits/stl_multiset.h: Likewise.
>>>	* include/bits/stl_set.h: Likewise.
>>>	* include/bits/stl_vector.h: Likewise.
>>>	* testsuite/23_containers/deque/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/forward_list/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/list/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/map/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/multimap/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/multiset/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/set/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/unordered_map/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/unordered_multimap/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/unordered_multiset/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/unordered_set/48101-3_neg.cc: New test.
>>>	* testsuite/23_containers/vector/48101-3_neg.cc: New test.
>>>
>>>Tested x86_64-linux, committed to trunk.
>>
>>this patch caused a couple of testsuite regressions:
>>
>>+FAIL: g++.old-deja/g++.other/headers1.C  -std=c++98 (test for excess errors)
>>+UNRESOLVED: g++.old-deja/g++.other/headers1.C  -std=c++98 compilation failed to produce executable
>>
>>Excess errors:
>>/var/gcc/regression/trunk/11-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/bits/stl_map.h:122:21: error: 'is_same' has not been declared
>>/var/gcc/regression/trunk/11-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/bits/stl_map.h:122:28: error: expected ',' or '...' before '<' token
>>/var/gcc/regression/trunk/11-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/bits/stl_multimap.h:121:21: error: 'is_same' has not been declared
>>/var/gcc/regression/trunk/11-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/bits/stl_multimap.h:121:28:
>>error: expected ',' or '...' before '<' token
>>
>>+FAIL: g++.old-deja/g++.robertl/eb109.C  -std=c++98 (test for excess errors)
>>
>>+FAIL: g++.dg/tree-ssa/copyprop.C   (test for excess errors)
>>
>>Same error, seen everywhere (i386-pc-solaris2.11, sparc-sun-solaris2.11,
>>aarch64-unknown-linux-gnu, x86_64-pc-linux-gnu, ...).
>
>Doh. In those files the existing static_assert wasn't guarded by a
>check for C++11 or later. I'm testing this patch.

Committed to trunk. Sorry about that.