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* [Bug libstdc++/107735] New: Inconsistent error messages for std::array out of bound @ 2022-11-17 15:00 andrzej at rpi dot pl 2022-11-17 16:31 ` [Bug c++/107735] " redi at gcc dot gnu.org ` (3 more replies) 0 siblings, 4 replies; 5+ messages in thread From: andrzej at rpi dot pl @ 2022-11-17 15:00 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107735 Bug ID: 107735 Summary: Inconsistent error messages for std::array out of bound Product: gcc Version: 12.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: libstdc++ Assignee: unassigned at gcc dot gnu.org Reporter: andrzej at rpi dot pl Target Milestone: --- Created attachment 53919 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53919&action=edit Preprocessed file The second and third lines of following code produce different `out of bound` compile errors, one pointing to the original line, the other pointing to a line inside standard library that is trying to access internal (non-std::) array ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ constexpr std::array<int, 3> array = {1, 2, 3}; constexpr int v1 = array[3]; constexpr int v2 = array[4]; ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Compilation line: `g++-12 a-minimal_example.ii` Compiler output: ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ minimal_example.cpp:6:27: error: array subscript value ‘3’ is outside the bounds of array type ‘std::__array_traits<int, 3>::_Type’ {aka ‘const int [3]’} 6 | constexpr int v1 = array[3]; | ^ In file included from minimal_example.cpp:1: minimal_example.cpp:9:27: in ‘constexpr’ expansion of ‘array.std::array<int, 3>::operator[](4)’ /usr/include/c++/12/array:219:25: in ‘constexpr’ expansion of ‘std::__array_traits<int, 3>::_S_ref(((const std::array<int, 3>*)this)->std::array<int, 3>::_M_elems, __n)’ /usr/include/c++/12/array:61:36: error: array subscript value ‘4’ is outside the bounds of array type ‘std::__array_traits<int, 3>::_Type’ {aka ‘const int [3]’} 61 | { return const_cast<_Tp&>(__t[__n]); } | ~~~^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GCC version: gcc-12 (Ubuntu 12.1.0-2ubuntu1~22.04) 12.1.0 System version: Linux 5.15.0-52-generic #58-Ubuntu SMP x86_64 GCC build options: Configured with: ../src/configure -v --with-pkgversion='Ubuntu 12.1.0-2ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-12/README.Bugs --enable-languages=c,ada,c++,go,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-12 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-12-sZcx2y/gcc-12-12.1.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-12-sZcx2y/gcc-12-12.1.0/debian/tmp-gcn/usr --enable-offload-defaulted --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107735] Inconsistent error messages for std::array out of bound 2022-11-17 15:00 [Bug libstdc++/107735] New: Inconsistent error messages for std::array out of bound andrzej at rpi dot pl @ 2022-11-17 16:31 ` redi at gcc dot gnu.org 2022-11-17 22:24 ` pinskia at gcc dot gnu.org ` (2 subsequent siblings) 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2022-11-17 16:31 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107735 Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Last reconfirmed| |2022-11-17 Status|UNCONFIRMED |NEW Ever confirmed|0 |1 Component|libstdc++ |c++ --- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> --- Libstdc++ doesn't print those errors, this is component=c++ ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107735] Inconsistent error messages for std::array out of bound 2022-11-17 15:00 [Bug libstdc++/107735] New: Inconsistent error messages for std::array out of bound andrzej at rpi dot pl 2022-11-17 16:31 ` [Bug c++/107735] " redi at gcc dot gnu.org @ 2022-11-17 22:24 ` pinskia at gcc dot gnu.org 2022-11-18 0:46 ` [Bug c++/107735] Inconsistent error messages for std::array out of bound due to taking the address of one-past-the-end is valid redi at gcc dot gnu.org 2022-11-18 0:49 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-11-17 22:24 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107735 --- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- I wonder if this is because doing constexpr const int *v1 = &array[3]; is valid and well defined. Even clang gives two different error messages: <source>:3:21: error: constexpr variable 'v1' must be initialized by a constant expression constexpr const int v1 = array[3]; ^ ~~~~~~~~ <source>:3:26: note: read of dereferenced one-past-the-end pointer is not allowed in a constant expression constexpr const int v1 = array[3]; ^ <source>:4:15: error: constexpr variable 'v2' must be initialized by a constant expression constexpr int v2 = array[4]; ^ ~~~~~~~~ /opt/compiler-explorer/gcc-snapshot/lib/gcc/x86_64-linux-gnu/13.0.0/../../../../include/c++/13.0.0/array:213:9: note: cannot refer to element 4 of array of 3 elements in a constant expression return _M_elems[__n]; ^ <source>:4:20: note: in call to '&array->operator[](4)' constexpr int v2 = array[4]; ^ ---- CUT ---- I do think clang's note of one-past-the-end gives more of a hint of why the error message is different though. And I do think GCC could add that note. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107735] Inconsistent error messages for std::array out of bound due to taking the address of one-past-the-end is valid 2022-11-17 15:00 [Bug libstdc++/107735] New: Inconsistent error messages for std::array out of bound andrzej at rpi dot pl 2022-11-17 16:31 ` [Bug c++/107735] " redi at gcc dot gnu.org 2022-11-17 22:24 ` pinskia at gcc dot gnu.org @ 2022-11-18 0:46 ` redi at gcc dot gnu.org 2022-11-18 0:49 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: redi at gcc dot gnu.org @ 2022-11-18 0:46 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107735 --- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Andrew Pinski from comment #2) > I wonder if this is because doing > constexpr const int *v1 = &array[3]; > > is valid and well defined. It's not, but &array.data()[3] is. I agree that's probably the reason for the different diagnostics. ^ permalink raw reply [flat|nested] 5+ messages in thread
* [Bug c++/107735] Inconsistent error messages for std::array out of bound due to taking the address of one-past-the-end is valid 2022-11-17 15:00 [Bug libstdc++/107735] New: Inconsistent error messages for std::array out of bound andrzej at rpi dot pl ` (2 preceding siblings ...) 2022-11-18 0:46 ` [Bug c++/107735] Inconsistent error messages for std::array out of bound due to taking the address of one-past-the-end is valid redi at gcc dot gnu.org @ 2022-11-18 0:49 ` pinskia at gcc dot gnu.org 3 siblings, 0 replies; 5+ messages in thread From: pinskia at gcc dot gnu.org @ 2022-11-18 0:49 UTC (permalink / raw) To: gcc-bugs https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107735 --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #3) > (In reply to Andrew Pinski from comment #2) > > I wonder if this is because doing > > constexpr const int *v1 = &array[3]; > > > > is valid and well defined. > > It's not, but &array.data()[3] is. > > I agree that's probably the reason for the different diagnostics. Interesting because both GCC and clang accept "constexpr const int *v1 = &array[3];" though. ^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2022-11-18 0:49 UTC | newest] Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2022-11-17 15:00 [Bug libstdc++/107735] New: Inconsistent error messages for std::array out of bound andrzej at rpi dot pl 2022-11-17 16:31 ` [Bug c++/107735] " redi at gcc dot gnu.org 2022-11-17 22:24 ` pinskia at gcc dot gnu.org 2022-11-18 0:46 ` [Bug c++/107735] Inconsistent error messages for std::array out of bound due to taking the address of one-past-the-end is valid redi at gcc dot gnu.org 2022-11-18 0:49 ` pinskia at gcc dot gnu.org
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