[libcxx-dev] [clang] 4ede887 - PR45402: Make the restrictions on constant evaluation of memcmp and
Richard Smith via libcxx-dev
libcxx-dev at lists.llvm.org
Sun Apr 5 15:17:43 PDT 2020
On Sun, 5 Apr 2020 at 14:44, David Zarzycki via cfe-commits <
cfe-commits at lists.llvm.org> wrote:
> We have overloaded builtins. Can that not solve __builtin_strlen?
>
I suppose it could, but we generally want __builtin_<libfunc> to behave the
same as <libfunc>. (The difference would not be visible most of the time,
but there's enough pre-existing use of __builtin_strlen through "clever"
macros and the like that I'd be worried that this would break something
important.) Maybe we should just make the mem* functions work again for
char8_t; then you can use __builtin_memchr(p, 0) - p as an optimized
compile-time strlen.
> --
> Sent from my iPhone
>
> On Apr 5, 2020, at 14:53, Richard Smith <richard at metafoo.co.uk> wrote:
>
>
> Thanks. We need to figure out what the right way to support char8_t with
> string builtins is. These ones could work in principle, whereas things like
> __builtin_strlen would never work because they take operands of the wrong
> types (and we can't cast const char8_t* -> const char* in a constant
> expression).
>
> On Sun, 5 Apr 2020 at 04:14, David Zarzycki via cfe-commits <
> cfe-commits at lists.llvm.org> wrote:
>
>> Hi Richard,
>>
>> I'm going to commit a narrow fix to clang to make the libcxx test suite
>> pass again by allowing char8_t again. If you feel that this is the wrong
>> long-term solution, please help the libcxx folks with whatever adjustments
>> they need.
>>
>> Thanks!
>>
>> Dave
>>
>>
>> On Sat, Apr 4, 2020, at 9:55 AM, David Zarzycki via libcxx-dev wrote:
>> > Hi Richard,
>> >
>> > This breaks libcxx. Can we please revert this or is a quick fix to
>> > libcxx possible?
>> >
>> >
>> > FAIL: libc++ ::
>> >
>> std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp
>> (58624 of 62672)
>> > ******************** TEST 'libc++ ::
>> >
>> std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp'
>> FAILED ********************
>> > Command: ['/p/tllvm/bin/clang++', '-o',
>> >
>> '/tmp/_update_lc/t/projects/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/Output/compare.pass.cpp.o',
>> '-x', 'c++',
>> '/home/dave/s/lp/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp',
>> '-c', '-v', '-Werror=thread-safety', '-std=c++2a', '-include',
>> '/home/dave/s/lp/libcxx/test/support/nasty_macros.h', '-nostdinc++',
>> '-I/home/dave/s/lp/libcxx/include',
>> '-I/tmp/_update_lc/t/projects/libcxx/include/c++build',
>> '-D__STDC_FORMAT_MACROS', '-D__STDC_LIMIT_MACROS',
>> '-D__STDC_CONSTANT_MACROS', '-I/home/dave/s/lp/libcxx/test/support',
>> '-ftemplate-depth=270', '-D_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER', '-Wall',
>> '-Wextra', '-Werror', '-Wuser-defined-warnings', '-Wshadow',
>> '-Wno-unused-command-line-argument', '-Wno-attributes',
>> '-Wno-pessimizing-move', '-Wno-c++11-extensions',
>> '-Wno-user-defined-literals', '-Wno-noexcept-type', '-Wsign-compare',
>> '-Wunused-variable', '-Wunused-parameter', '-Wunreachable-code', '-c']
>> > Exit Code: 1
>> > Standard Error:
>> > --
>> > clang version 11.0.0 (https://github.com/llvm/llvm-project.git
>> > 22127da8f17c03c69231f3631472f7f99ad9cb7f)
>> > Target: x86_64-unknown-linux-gnu
>> > Thread model: posix
>> > InstalledDir: /p/tllvm/bin
>> > Found candidate GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
>> > Selected GCC installation: /usr/lib/gcc/x86_64-redhat-linux/9
>> > Candidate multilib: .;@m64
>> > Candidate multilib: 32;@m32
>> > Selected multilib: .;@m64
>> > (in-process)
>> > "/p/tllvm/bin/clang-11" -cc1 -triple x86_64-unknown-linux-gnu
>> > -emit-obj -mrelax-all -disable-free -disable-llvm-verifier
>> > -discard-value-names -main-file-name compare.pass.cpp
>> > -mrelocation-model static -mthread-model posix -mframe-pointer=all
>> > -fmath-errno -fno-rounding-math -mconstructor-aliases -munwind-tables
>> > -target-cpu x86-64 -dwarf-column-info -fno-split-dwarf-inlining
>> > -debugger-tuning=gdb -v -nostdinc++ -resource-dir
>> > /p/tllvm/lib64/clang/11.0.0 -include
>> > /home/dave/s/lp/libcxx/test/support/nasty_macros.h -I
>> > /home/dave/s/lp/libcxx/include -I
>> > /tmp/_update_lc/t/projects/libcxx/include/c++build -D
>> > __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -D __STDC_CONSTANT_MACROS
>> > -I /home/dave/s/lp/libcxx/test/support -D
>> > _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER -internal-isystem
>> > /usr/local/include -internal-isystem
>> > /p/tllvm/lib64/clang/11.0.0/include -internal-externc-isystem /include
>> > -internal-externc-isystem /usr/include -Werror=thread-safety -Wall
>> > -Wextra -Werror -Wuser-defined-warnings -Wshadow
>> > -Wno-unused-command-line-argument -Wno-attributes -Wno-pessimizing-move
>> > -Wno-c++11-extensions -Wno-user-defined-literals -Wno-noexcept-type
>> > -Wsign-compare -Wunused-variable -Wunused-parameter -Wunreachable-code
>> > -std=c++2a -fdeprecated-macro -fdebug-compilation-dir
>> >
>> /tmp/_update_lc/t/projects/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t
>> -ftemplate-depth 270 -ferror-limit 19 -fgnuc-version=4.2.1
>> -fno-implicit-modules -fcxx-exceptions -fexceptions -faddrsig -o
>> /tmp/_update_lc/t/projects/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/Output/compare.pass.cpp.o
>> -x c++
>> /home/dave/s/lp/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp
>> > clang -cc1 version 11.0.0 based upon LLVM 11.0.0git default target
>> > x86_64-unknown-linux-gnu
>> > ignoring nonexistent directory "/include"
>> > #include "..." search starts here:
>> > #include <...> search starts here:
>> > /home/dave/s/lp/libcxx/include
>> > /tmp/_update_lc/t/projects/libcxx/include/c++build
>> > /home/dave/s/lp/libcxx/test/support
>> > /usr/local/include
>> > /p/tllvm/lib64/clang/11.0.0/include
>> > /usr/include
>> > End of search list.
>> >
>> /home/dave/s/lp/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp:53:19:
>> error: static_assert expression is not an integral constant expression
>> > static_assert(test_constexpr(), "" );
>> > ^~~~~~~~~~~~~~~~
>> > /home/dave/s/lp/libcxx/include/__string:662:12: note: constant
>> > evaluation of '__builtin_memcmp' between arrays of types 'const
>> > char8_t' and 'const char8_t' is not supported; only arrays of narrow
>> > character types can be compared
>> > return __builtin_memcmp(__s1, __s2, __n);
>> > ^
>> >
>> /home/dave/s/lp/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp:24:12:
>> note: in call to 'compare(&u8"123"[0], &u8"223"[0], 3)'
>> > return std::char_traits<char8_t>::compare(u8"123", u8"223", 3) < 0
>> > ^
>> >
>> /home/dave/s/lp/libcxx/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp:53:19:
>> note: in call to 'test_constexpr()'
>> > static_assert(test_constexpr(), "" );
>> > ^
>> > 1 error generated.
>> > --
>> >
>> > Compilation failed unexpectedly!
>> > ********************
>> >
>> > Testing Time: 135.49s
>> > ********************
>> > Failing Tests (1):
>> > libc++ ::
>> >
>> std/strings/char.traits/char.traits.specializations/char.traits.specializations.char8_t/compare.pass.cpp
>> >
>> > Expected Passes : 45503
>> > Expected Failures : 118
>> > Unsupported Tests : 17050
>> > Unexpected Failures: 1
>> >
>> >
>> > On Fri, Apr 3, 2020, at 9:26 PM, Richard Smith via cfe-commits wrote:
>> > >
>> > > Author: Richard Smith
>> > > Date: 2020-04-03T18:26:14-07:00
>> > > New Revision: 4ede8879924c08ae5b495d3f421c167d822a60be
>> > >
>> > > URL:
>> > >
>> https://github.com/llvm/llvm-project/commit/4ede8879924c08ae5b495d3f421c167d822a60be
>> > > DIFF:
>> > >
>> https://github.com/llvm/llvm-project/commit/4ede8879924c08ae5b495d3f421c167d822a60be.diff
>> > >
>> > > LOG: PR45402: Make the restrictions on constant evaluation of memcmp
>> and
>> > > memchr consistent and comprehensible, and document them.
>> > >
>> > > We previously allowed evaluation of memcmp on arrays of integers of
>> any
>> > > size, so long as the call evaluated to 0, and allowed evaluation of
>> > > memchr on any array of integral type of size 1 (including enums). The
>> > > purpose of constant-evaluating these builtins is only to support
>> > > constexpr std::char_traits, so we now consistently allow them on
>> arrays
>> > > of (possibly signed or unsigned) char only.
>> > >
>> > > Added:
>> > >
>> > >
>> > > Modified:
>> > > clang/docs/LanguageExtensions.rst
>> > > clang/include/clang/Basic/DiagnosticASTKinds.td
>> > > clang/lib/AST/ExprConstant.cpp
>> > > clang/test/SemaCXX/constexpr-string.cpp
>> > >
>> > > Removed:
>> > >
>> > >
>> > >
>> > >
>> ################################################################################
>> > > diff --git a/clang/docs/LanguageExtensions.rst
>> > > b/clang/docs/LanguageExtensions.rst
>> > > index 558ce7dee653..6dcfd1a49f06 100644
>> > > --- a/clang/docs/LanguageExtensions.rst
>> > > +++ b/clang/docs/LanguageExtensions.rst
>> > > @@ -2333,10 +2333,11 @@ String builtins
>> > > ---------------
>> > >
>> > > Clang provides constant expression evaluation support for builtins
>> forms of
>> > > -the following functions from the C standard library ``<string.h>``
>> header:
>> > > +the following functions from the C standard library headers
>> > > +``<string.h>`` and ``<wchar.h>``:
>> > >
>> > > * ``memchr``
>> > > -* ``memcmp``
>> > > +* ``memcmp`` (and its deprecated BSD / POSIX alias ``bcmp``)
>> > > * ``strchr``
>> > > * ``strcmp``
>> > > * ``strlen``
>> > > @@ -2366,7 +2367,11 @@ In addition to the above, one further builtin
>> is
>> > > provided:
>> > > constant expressions in C++11 onwards (where a cast from ``void*``
>> to
>> > > ``char*``
>> > > is disallowed in general).
>> > >
>> > > -Support for constant expression evaluation for the above builtins be
>> > > detected
>> > > +Constant evaluation support for the ``__builtin_mem*`` functions is
>> > > provided
>> > > +only for arrays of ``char``, ``signed char``, or ``unsigned char``,
>> > > despite
>> > > +these functions accepting an argument of type ``const void*``.
>> > > +
>> > > +Support for constant expression evaluation for the above builtins
>> can
>> > > be detected
>> > > with ``__has_feature(cxx_constexpr_string_builtins)``.
>> > >
>> > > Memory builtins
>> > > @@ -2386,6 +2391,25 @@ more information.
>> > >
>> > > Note that the `size` argument must be a compile time constant.
>> > >
>> > > +Clang provides constant expression evaluation support for builtin
>> > > forms of the
>> > > +following functions from the C standard library headers
>> > > +``<string.h>`` and ``<wchar.h>``:
>> > > +
>> > > +* ``memcpy``
>> > > +* ``memmove``
>> > > +* ``wmemcpy``
>> > > +* ``wmemmove``
>> > > +
>> > > +In each case, the builtin form has the name of the C library
>> function
>> > > prefixed
>> > > +by ``__builtin_``.
>> > > +
>> > > +Constant evaluation support is only provided when the source and
>> > > destination
>> > > +are pointers to arrays with the same trivially copyable element
>> type,
>> > > and the
>> > > +given size is an exact multiple of the element size that is no
>> greater
>> > > than
>> > > +the number of elements accessible through the source and destination
>> > > operands.
>> > > +
>> > > +Constant evaluation support is not yet provided for
>> > > ``__builtin_memcpy_inline``.
>> > > +
>> > > Atomic Min/Max builtins with memory ordering
>> > > --------------------------------------------
>> > >
>> > >
>> > > diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td
>> > > b/clang/include/clang/Basic/DiagnosticASTKinds.td
>> > > index 544573edffdf..a1415f9ec0e1 100644
>> > > --- a/clang/include/clang/Basic/DiagnosticASTKinds.td
>> > > +++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
>> > > @@ -244,6 +244,12 @@ def note_constexpr_unsupported_unsized_array :
>> > > Note<
>> > > def note_constexpr_unsized_array_indexed : Note<
>> > > "indexing of array without known bound is not allowed "
>> > > "in a constant expression">;
>> > > +def note_constexpr_memcmp_unsupported : Note<
>> > > + "constant evaluation of %0 between arrays of types %1 and %2 "
>> > > + "is not supported; only arrays of narrow character types can be
>> > > compared">;
>> > > +def note_constexpr_memchr_unsupported : Note<
>> > > + "constant evaluation of %0 on array of type %1 "
>> > > + "is not supported; only arrays of narrow character types can be
>> > > searched">;
>> > > def note_constexpr_memcpy_null : Note<
>> > > "%select{source|destination}2 of "
>> > > "'%select{%select{memcpy|wmemcpy}1|%select{memmove|wmemmove}1}0' "
>> > >
>> > > diff --git a/clang/lib/AST/ExprConstant.cpp
>> > > b/clang/lib/AST/ExprConstant.cpp
>> > > index c6e1cc7b67df..a83b2e24e17f 100644
>> > > --- a/clang/lib/AST/ExprConstant.cpp
>> > > +++ b/clang/lib/AST/ExprConstant.cpp
>> > > @@ -8469,8 +8469,12 @@ bool
>> > > PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
>> > > }
>> > > // Give up on byte-oriented matching against multibyte elements.
>> > > // FIXME: We can compare the bytes in the correct order.
>> > > - if (IsRawByte && Info.Ctx.getTypeSizeInChars(CharTy) !=
>> > > CharUnits::One())
>> > > + if (IsRawByte && !CharTy->isCharType()) {
>> > > + Info.FFDiag(E, diag::note_constexpr_memchr_unsupported)
>> > > + << (std::string("'") +
>> > > Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'")
>> > > + << CharTy;
>> > > return false;
>> > > + }
>> > > // Figure out what value we're actually looking for (after
>> > > converting to
>> > > // the corresponding unsigned type if necessary).
>> > > uint64_t DesiredVal;
>> > > @@ -8586,6 +8590,7 @@ bool
>> > > PointerExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
>> > > QualType T = Dest.Designator.getType(Info.Ctx);
>> > > QualType SrcT = Src.Designator.getType(Info.Ctx);
>> > > if (!Info.Ctx.hasSameUnqualifiedType(T, SrcT)) {
>> > > + // FIXME: Consider using our bit_cast implementation to
>> support
>> > > this.
>> > > Info.FFDiag(E, diag::note_constexpr_memcpy_type_pun) << Move
>> <<
>> > > SrcT << T;
>> > > return false;
>> > > }
>> > > @@ -11149,6 +11154,16 @@ bool
>> > > IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
>> > > CharTy1, E->getArg(0)->getType()->getPointeeType())
>> &&
>> > > Info.Ctx.hasSameUnqualifiedType(CharTy1, CharTy2)));
>> > >
>> > > + // For memcmp, allow comparing any arrays of '[[un]signed] char',
>> > > + // but no other types.
>> > > + if (IsRawByte && !(CharTy1->isCharType() &&
>> > > CharTy2->isCharType())) {
>> > > + // FIXME: Consider using our bit_cast implementation to
>> support
>> > > this.
>> > > + Info.FFDiag(E, diag::note_constexpr_memcmp_unsupported)
>> > > + << (std::string("'") +
>> > > Info.Ctx.BuiltinInfo.getName(BuiltinOp) + "'")
>> > > + << CharTy1 << CharTy2;
>> > > + return false;
>> > > + }
>> > > +
>> > > const auto &ReadCurElems = [&](APValue &Char1, APValue &Char2) {
>> > > return handleLValueToRValueConversion(Info, E, CharTy1,
>> String1,
>> > > Char1) &&
>> > > handleLValueToRValueConversion(Info, E, CharTy2,
>> String2,
>> > > Char2) &&
>> > > @@ -11159,57 +11174,6 @@ bool
>> > > IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
>> > > HandleLValueArrayAdjustment(Info, E, String2, CharTy2,
>> 1);
>> > > };
>> > >
>> > > - if (IsRawByte) {
>> > > - uint64_t BytesRemaining = MaxLength;
>> > > - // Pointers to const void may point to objects of incomplete
>> > > type.
>> > > - if (CharTy1->isIncompleteType()) {
>> > > - Info.FFDiag(E, diag::note_constexpr_ltor_incomplete_type) <<
>> > > CharTy1;
>> > > - return false;
>> > > - }
>> > > - if (CharTy2->isIncompleteType()) {
>> > > - Info.FFDiag(E, diag::note_constexpr_ltor_incomplete_type) <<
>> > > CharTy2;
>> > > - return false;
>> > > - }
>> > > - uint64_t CharTy1Width{Info.Ctx.getTypeSize(CharTy1)};
>> > > - CharUnits CharTy1Size =
>> > > Info.Ctx.toCharUnitsFromBits(CharTy1Width);
>> > > - // Give up on comparing between elements with disparate widths.
>> > > - if (CharTy1Size != Info.Ctx.getTypeSizeInChars(CharTy2))
>> > > - return false;
>> > > - uint64_t BytesPerElement = CharTy1Size.getQuantity();
>> > > - assert(BytesRemaining && "BytesRemaining should not be zero:
>> the
>> > > "
>> > > - "following loop considers at least
>> one
>> > > element");
>> > > - while (true) {
>> > > - APValue Char1, Char2;
>> > > - if (!ReadCurElems(Char1, Char2))
>> > > - return false;
>> > > - // We have compatible in-memory widths, but a possible type
>> and
>> > > - // (for `bool`) internal representation mismatch.
>> > > - // Assuming two's complement representation, including 0 for
>> > > `false` and
>> > > - // 1 for `true`, we can check an appropriate number of
>> > > elements for
>> > > - // equality even if they are not byte-sized.
>> > > - APSInt Char1InMem = Char1.getInt().extOrTrunc(CharTy1Width);
>> > > - APSInt Char2InMem = Char2.getInt().extOrTrunc(CharTy1Width);
>> > > - if (Char1InMem.ne(Char2InMem)) {
>> > > - // If the elements are byte-sized, then we can produce a
>> > > three-way
>> > > - // comparison result in a straightforward manner.
>> > > - if (BytesPerElement == 1u) {
>> > > - // memcmp always compares unsigned chars.
>> > > - return Success(Char1InMem.ult(Char2InMem) ? -1 : 1, E);
>> > > - }
>> > > - // The result is byte-order sensitive, and we have
>> multibyte
>> > > elements.
>> > > - // FIXME: We can compare the remaining bytes in the
>> correct
>> > > order.
>> > > - return false;
>> > > - }
>> > > - if (!AdvanceElems())
>> > > - return false;
>> > > - if (BytesRemaining <= BytesPerElement)
>> > > - break;
>> > > - BytesRemaining -= BytesPerElement;
>> > > - }
>> > > - // Enough elements are equal to account for the memcmp limit.
>> > > - return Success(0, E);
>> > > - }
>> > > -
>> > > bool StopAtNull =
>> > > (BuiltinOp != Builtin::BImemcmp && BuiltinOp !=
>> > > Builtin::BIbcmp &&
>> > > BuiltinOp != Builtin::BIwmemcmp &&
>> > > @@ -11227,7 +11191,7 @@ bool
>> > > IntExprEvaluator::VisitBuiltinCallExpr(const CallExpr *E,
>> > > APValue Char1, Char2;
>> > > if (!ReadCurElems(Char1, Char2))
>> > > return false;
>> > > - if (Char1.getInt() != Char2.getInt()) {
>> > > + if (Char1.getInt().ne(Char2.getInt())) {
>> > > if (IsWide) // wmemcmp compares with wchar_t signedness.
>> > > return Success(Char1.getInt() < Char2.getInt() ? -1 : 1,
>> E);
>> > > // memcmp always compares unsigned chars.
>> > >
>> > > diff --git a/clang/test/SemaCXX/constexpr-string.cpp
>> > > b/clang/test/SemaCXX/constexpr-string.cpp
>> > > index f540be8f8e5b..79ac3bf2cc4d 100644
>> > > --- a/clang/test/SemaCXX/constexpr-string.cpp
>> > > +++ b/clang/test/SemaCXX/constexpr-string.cpp
>> > > @@ -47,7 +47,7 @@ extern "C" {
>> > > extern wchar_t *wmemmove(wchar_t *d, const wchar_t *s, size_t n);
>> > > }
>> > >
>> > > -# 45 "SemaCXX/constexpr-string.cpp" 2
>> > > +# 51 "SemaCXX/constexpr-string.cpp" 2
>> > > namespace Strlen {
>> > > constexpr int n = __builtin_strlen("hello"); // ok
>> > > static_assert(n == 5);
>> > > @@ -121,13 +121,13 @@ namespace StrcmpEtc {
>> > > extern struct Incomplete incomplete;
>> > > static_assert(__builtin_memcmp(&incomplete, "", 0u) == 0);
>> > > static_assert(__builtin_memcmp("", &incomplete, 0u) == 0);
>> > > - static_assert(__builtin_memcmp(&incomplete, "", 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{read of
>> > > incomplete type 'struct Incomplete'}}
>> > > - static_assert(__builtin_memcmp("", &incomplete, 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{read of
>> > > incomplete type 'struct Incomplete'}}
>> > > + static_assert(__builtin_memcmp(&incomplete, "", 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{not
>> > > supported}}
>> > > + static_assert(__builtin_memcmp("", &incomplete, 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{not
>> > > supported}}
>> > >
>> > > static_assert(__builtin_bcmp(&incomplete, "", 0u) == 0);
>> > > static_assert(__builtin_bcmp("", &incomplete, 0u) == 0);
>> > > - static_assert(__builtin_bcmp(&incomplete, "", 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{read of
>> > > incomplete type 'struct Incomplete'}}
>> > > - static_assert(__builtin_bcmp("", &incomplete, 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{read of
>> > > incomplete type 'struct Incomplete'}}
>> > > + static_assert(__builtin_bcmp(&incomplete, "", 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{not
>> > > supported}}
>> > > + static_assert(__builtin_bcmp("", &incomplete, 1u) == 42); //
>> > > expected-error {{not an integral constant}} expected-note {{not
>> > > supported}}
>> > >
>> > > constexpr unsigned char ku00fe00[] = {0x00, 0xfe, 0x00};
>> > > constexpr unsigned char ku00feff[] = {0x00, 0xfe, 0xff};
>> > > @@ -155,11 +155,11 @@ namespace StrcmpEtc {
>> > >
>> > > struct Bool3Tuple { bool bb[3]; };
>> > > constexpr Bool3Tuple kb000100 = {{false, true, false}};
>> > > - static_assert(sizeof(bool) != 1u || __builtin_memcmp(ks00fe00,
>> > > kb000100.bb, 1) == 0);
>> > > - static_assert(sizeof(bool) != 1u || __builtin_memcmp(ks00fe00,
>> > > kb000100.bb, 2) == 1);
>> > > + static_assert(sizeof(bool) != 1u || __builtin_memcmp(ks00fe00,
>> > > kb000100.bb, 1) == 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > > + static_assert(sizeof(bool) != 1u || __builtin_memcmp(ks00fe00,
>> > > kb000100.bb, 2) == 1); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > >
>> > > - static_assert(sizeof(bool) != 1u || __builtin_bcmp(ks00fe00,
>> > > kb000100.bb, 1) == 0);
>> > > - static_assert(sizeof(bool) != 1u || __builtin_bcmp(ks00fe00,
>> > > kb000100.bb, 2) != 0);
>> > > + static_assert(sizeof(bool) != 1u || __builtin_bcmp(ks00fe00,
>> > > kb000100.bb, 1) == 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > > + static_assert(sizeof(bool) != 1u || __builtin_bcmp(ks00fe00,
>> > > kb000100.bb, 2) != 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > >
>> > > constexpr long ksl[] = {0, -1};
>> > > constexpr unsigned int kui[] = {0, 0u - 1};
>> > > @@ -173,25 +173,25 @@ namespace StrcmpEtc {
>> > > return nullptr;
>> > > }
>> > > }
>> > > - static_assert(__builtin_memcmp(ksl, kuSizeofLong(), sizeof(long) -
>> > > 1) == 0);
>> > > - static_assert(__builtin_memcmp(ksl, kuSizeofLong(), sizeof(long) +
>> > > 0) == 0);
>> > > - static_assert(__builtin_memcmp(ksl, kuSizeofLong(), sizeof(long) +
>> > > 1) == 0);
>> > > - static_assert(__builtin_memcmp(ksl, kuSizeofLong(), 2*sizeof(long)
>> -
>> > > 1) == 0);
>> > > - static_assert(__builtin_memcmp(ksl, kuSizeofLong(), 2*sizeof(long)
>> +
>> > > 0) == 0);
>> > > - static_assert(__builtin_memcmp(ksl, kuSizeofLong(), 2*sizeof(long)
>> +
>> > > 1) == 42); // expected-error {{not an integral constant}}
>> expected-note
>> > > {{dereferenced one-past-the-end}}
>> > > - static_assert(__builtin_memcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) - 1) == 0);
>> > > - static_assert(__builtin_memcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 0) == 0);
>> > > - static_assert(__builtin_memcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 1) == 42); // expected-error {{not an integral
>> > > constant}} expected-note {{dereferenced one-past-the-end}}
>> > > -
>> > > - static_assert(__builtin_bcmp(ksl, kuSizeofLong(), sizeof(long) -
>> 1)
>> > > == 0);
>> > > - static_assert(__builtin_bcmp(ksl, kuSizeofLong(), sizeof(long) +
>> 0)
>> > > == 0);
>> > > - static_assert(__builtin_bcmp(ksl, kuSizeofLong(), sizeof(long) +
>> 1)
>> > > == 0);
>> > > - static_assert(__builtin_bcmp(ksl, kuSizeofLong(), 2*sizeof(long) -
>> > > 1) == 0);
>> > > - static_assert(__builtin_bcmp(ksl, kuSizeofLong(), 2*sizeof(long) +
>> > > 0) == 0);
>> > > - static_assert(__builtin_bcmp(ksl, kuSizeofLong(), 2*sizeof(long) +
>> > > 1) == 42); // expected-error {{not an integral constant}}
>> expected-note
>> > > {{dereferenced one-past-the-end}}
>> > > - static_assert(__builtin_bcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) - 1) == 0);
>> > > - static_assert(__builtin_bcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 0) == 0);
>> > > - static_assert(__builtin_bcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 1) == 42); // expected-error {{not an integral
>> > > constant}} expected-note {{dereferenced one-past-the-end}}
>> > > + static_assert(__builtin_memcmp(ksl, kuSizeofLong(), sizeof(long) -
>> > > 1) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_memcmp(ksl, kuSizeofLong(), sizeof(long) +
>> > > 0) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_memcmp(ksl, kuSizeofLong(), sizeof(long) +
>> > > 1) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_memcmp(ksl, kuSizeofLong(), 2*sizeof(long)
>> -
>> > > 1) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_memcmp(ksl, kuSizeofLong(), 2*sizeof(long)
>> +
>> > > 0) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_memcmp(ksl, kuSizeofLong(), 2*sizeof(long)
>> +
>> > > 1) == 42); // expected-error {{constant}} expected-note {{not
>> > > supported}}
>> > > + static_assert(__builtin_memcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) - 1) == 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > > + static_assert(__builtin_memcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 0) == 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > > + static_assert(__builtin_memcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 1) == 42); // expected-error {{constant}}
>> expected-note
>> > > {{not supported}}
>> > > +
>> > > + static_assert(__builtin_bcmp(ksl, kuSizeofLong(), sizeof(long) -
>> 1)
>> > > == 0); // expected-error {{constant}} expected-note {{not supported}}
>> > > + static_assert(__builtin_bcmp(ksl, kuSizeofLong(), sizeof(long) +
>> 0)
>> > > == 0); // expected-error {{constant}} expected-note {{not supported}}
>> > > + static_assert(__builtin_bcmp(ksl, kuSizeofLong(), sizeof(long) +
>> 1)
>> > > == 0); // expected-error {{constant}} expected-note {{not supported}}
>> > > + static_assert(__builtin_bcmp(ksl, kuSizeofLong(), 2*sizeof(long) -
>> > > 1) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_bcmp(ksl, kuSizeofLong(), 2*sizeof(long) +
>> > > 0) == 0); // expected-error {{constant}} expected-note {{not
>> supported}}
>> > > + static_assert(__builtin_bcmp(ksl, kuSizeofLong(), 2*sizeof(long) +
>> > > 1) == 42); // expected-error {{constant}} expected-note {{not
>> > > supported}}
>> > > + static_assert(__builtin_bcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) - 1) == 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > > + static_assert(__builtin_bcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 0) == 0); // expected-error {{constant}} expected-note
>> > > {{not supported}}
>> > > + static_assert(__builtin_bcmp(ksl + 1, kuSizeofLong() + 1,
>> > > sizeof(long) + 1) == 42); // expected-error {{constant}}
>> expected-note
>> > > {{not supported}}
>> > >
>> > > constexpr int a = strcmp("hello", "world"); // expected-error
>> > > {{constant expression}} expected-note {{non-constexpr function
>> 'strcmp'
>> > > cannot be used in a constant expression}}
>> > > constexpr int b = strncmp("hello", "world", 3); // expected-error
>> > > {{constant expression}} expected-note {{non-constexpr function
>> > > 'strncmp' cannot be used in a constant expression}}
>> > > @@ -385,14 +385,14 @@ namespace StrchrEtc {
>> > > enum class E : unsigned char {};
>> > > struct EPair { E e, f; };
>> > > constexpr EPair ee{E{240}};
>> > > - static_assert(__builtin_memchr(&ee.e, 240, 1) == &ee.e);
>> > > + static_assert(__builtin_memchr(&ee.e, 240, 1) == &ee.e); //
>> > > expected-error {{constant}} expected-note {{not supported}}
>> > >
>> > > constexpr bool kBool[] = {false, true, false};
>> > > constexpr const bool *const kBoolPastTheEndPtr = kBool + 3;
>> > > - static_assert(sizeof(bool) != 1u ||
>> > > __builtin_memchr(kBoolPastTheEndPtr - 3, 1, 99) == kBool + 1);
>> > > - static_assert(sizeof(bool) != 1u || __builtin_memchr(kBool + 1, 0,
>> > > 99) == kBoolPastTheEndPtr - 1);
>> > > - static_assert(sizeof(bool) != 1u ||
>> > > __builtin_memchr(kBoolPastTheEndPtr - 3, -1, 3) == nullptr);
>> > > - static_assert(sizeof(bool) != 1u ||
>> > > __builtin_memchr(kBoolPastTheEndPtr, 0, 1) == nullptr); //
>> > > expected-error {{not an integral constant}} expected-note
>> > > {{dereferenced one-past-the-end}}
>> > > + static_assert(sizeof(bool) != 1u ||
>> > > __builtin_memchr(kBoolPastTheEndPtr - 3, 1, 99) == kBool + 1); //
>> > > expected-error {{constant}} expected-note {{not supported}}
>> > > + static_assert(sizeof(bool) != 1u || __builtin_memchr(kBool + 1, 0,
>> > > 99) == kBoolPastTheEndPtr - 1); // expected-error {{constant}}
>> > > expected-note {{not supported}}
>> > > + static_assert(sizeof(bool) != 1u ||
>> > > __builtin_memchr(kBoolPastTheEndPtr - 3, -1, 3) == nullptr); //
>> > > expected-error {{constant}} expected-note {{not supported}}
>> > > + static_assert(sizeof(bool) != 1u ||
>> > > __builtin_memchr(kBoolPastTheEndPtr, 0, 1) == nullptr); //
>> > > expected-error {{constant}} expected-note {{not supported}}
>> > >
>> > > static_assert(__builtin_char_memchr(kStr, 'a', 0) == nullptr);
>> > > static_assert(__builtin_char_memchr(kStr, 'a', 1) == kStr);
>> > >
>> > >
>> > >
>> > > _______________________________________________
>> > > cfe-commits mailing list
>> > > cfe-commits at lists.llvm.org
>> > > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>> > >
>> > _______________________________________________
>> > libcxx-dev mailing list
>> > libcxx-dev at lists.llvm.org
>> > https://lists.llvm.org/cgi-bin/mailman/listinfo/libcxx-dev
>> >
>> _______________________________________________
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>>
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