Closed arthaud closed 5 years ago
It looks like this will be fixed in libc++: https://bugs.llvm.org/show_bug.cgi?id=40230
Thanks for the report. This nasty pair class was used to portably support all compilers (including C++03 compilers, where std::pair had no move semantics or placement constructors.) One workaround is to embed an internal std::pair inside the dtl::pair class to guarantee excatly the same memory layout.
The second step would be to use the native std::pair on compilers withou full C++11 support.
I'll try the first workaround in the following days and inform about progress in this bug.
The first workaround is not possible because pair exposes "first" and "second" as public members. We can try to reproduce the padding in libcpp with the following patch. Could please test it, as I haven't been able to set up the virtual machine yet? boost_container_libcpp.txt
Thanks for the patch. Unfortunately I'm getting the following error:
$ c++ test.cpp -I/tmp/boost/include
In file included from test.cpp:3:
In file included from /tmp/boost/include/container/include/boost/container/flat_map.hpp:29:
In file included from /tmp/boost/include/container/include/boost/container/detail/flat_tree.hpp:29:
/tmp/boost/include/container/include/boost/container/detail/pair.hpp:211:67: error: too many arguments provided to function-like macro invocation
: pair_padding<T1, T2, offsetof(std::pair<T1 BOOST_MOVE_I T2>, first) >
^
/usr/include/sys/cdefs.h:476:9: note: macro '__offsetof' defined here
#define __offsetof(type, field) __builtin_offsetof(type, field)
^
In file included from test.cpp:3:
In file included from /tmp/boost/include/container/include/boost/container/flat_map.hpp:29:
In file included from /tmp/boost/include/container/include/boost/container/detail/flat_tree.hpp:29:
/tmp/boost/include/container/include/boost/container/detail/pair.hpp:211:27: error: use of undeclared identifier '__offsetof'
: pair_padding<T1, T2, offsetof(std::pair<T1 BOOST_MOVE_I T2>, first) >
^
/usr/include/stddef.h:75:31: note: expanded from macro 'offsetof'
#define offsetof(type, field) __offsetof(type, field)
^
In file included from test.cpp:3:
In file included from /tmp/boost/include/container/include/boost/container/flat_map.hpp:29:
In file included from /tmp/boost/include/container/include/boost/container/detail/flat_tree.hpp:29:
/tmp/boost/include/container/include/boost/container/detail/pair.hpp:213:1: error: expected class name
{
^
3 errors generated.
Regarding the patch, I would like to suggest to check for _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
instead of _LIBCPP_VERSION
. This will avoid possible regressions on most systems and save compile time.
It compiles with -std=c++11
but the bug is still there, I'm trying to investigate this.
EDIT: It was an error on my side. It still doesn't compile with -std=c++11
EDIT 2: It looks like a common macro problem, where the comma in std::pair< T1, T2 >
is treated as an argument separator for the macro offset_of
. This is probably why you tried to use BOOST_MOVE_I
but it didn't work.
I've reproduced the problem in Linux using clang -stdlib=libc++ and defining "_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR".
New patch attached, the patch boost_container_pair_libcpp_patch.txt compiles in C++03 and C++2a modes.
I confirm that the patch fixes the issue, thank you.
Many thanks for the report and help solving the issue. Fixed in commit:
https://github.com/boostorg/container/commit/2b5197a5cb65a752b72296e441b2b211ebe8d2d2
There was a typo in the committed patch, corrected with commit:
https://github.com/boostorg/container/commit/80789255b9e143e2c23e171f63872e001bc1b5c5
Hi everyone,
I found a bug in
boost::container::flat_map
on FreeBSD.System: FreeBSD 12.0 Compiler: Clang 6.0.1 with libc++ (default compiler on FreeBSD) Boost: master branch on Github
See the following example:
Output:
2, 3, 0
Expected:1, 2, 3
flat_map
usesboost::container::dtl::pair
internally and uses reinterpret_casts to expose astd::pair
in the iterators, see flat_map.hpp#L66 and flat_map.hpp#L547The problem is that
std::pair
andboost::container::dtl::pair
have a different memory layout!See the following example:
Output:
std::pair
has a weird padding of 1 byte at the beginning. I think this is related to this patch: https://reviews.llvm.org/D25389 I think there might be a problem with the base class__non_trivially_copyable_base
. It looks like the EBO doesn't work properly.I'm not sure what to do to fix this. I think the C++ standard doesn't enforce the layout of
std::pair
to be{first, second}
, so maybe boost shouldn't assume this.To reproduce this, I used the following virtual machine: https://download.freebsd.org/ftp/releases/VM-IMAGES/12.0-RELEASE/amd64/Latest/ Upstream bug in IKOS: https://github.com/NASA-SW-VnV/ikos/issues/22