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https://issues.apache.org/jira/browse/MESOS-9718?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16814600#comment-16814600
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Joseph Wu edited comment on MESOS-9718 at 4/10/19 4:10 PM:
-----------------------------------------------------------
Looks like this error occurs because in C+\+20, a string literal like
{{u8"..."}} translates into a {{const char8_t[N]}}, whereas in earlier C++
versions, the same expression gives a {{const char[N]}} type. We can implicitly
convert to {{std::string}} from {{const char[N]}}, but not from {{const
char8_t[N]}}, which should be held by a {{std::u8string}}.
I'm not sure if there is a quick fix for this, since we're still on C++14 or so.
Here's some further reading:
[http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0482r3.html]
was (Author: kaysoky):
Looks like this error occurs because in C++20, a string literal like
{{u8"..."}} translates into a {{const char8_t[N]}}, whereas in earlier C++
versions, the same expression gives a {{const char[N]}} type. We can
implicitly convert to {{std::string}} from {{const char[N]}}, but not from
{{const char8_t[N]}}, which should be held by a {{std::u8string}}.
I'm not sure if there is a quick fix for this, since we're still on C++14 or so.
Here's some further reading:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2018/p0482r3.html
> Compile failures with char8_t by MSVC under /std:c++latest mode
> ---------------------------------------------------------------
>
> Key: MESOS-9718
> URL: https://issues.apache.org/jira/browse/MESOS-9718
> Project: Mesos
> Issue Type: Bug
> Components: build
> Reporter: QuellaZhang
> Priority: Major
> Labels: windows
>
> Hi All,
> We've stumbled across some build failures in Mesos after implementing support
> for char8_t under /std:c + + +latest in the development version of Visual C+
> + +. Could you help look at this? Thanks in advance! Noted that this issue
> only found when compiles with unreleased vctoolset, that next release of MSVC
> will have this behavior.
> *Repro steps:*
> git clone -c core.autocrlf=true [https://github.com/apache/mesos]
> D:\mesos\src
> open a VS 2017 x64 command prompt as admin and browse to D:\mesos
> set _CL_=/std:c++latest
> cd src
> .\bootstrap.bat
> cd ..
> mkdir build_x64 && pushd build_x64
> cmake ..\src -G "Visual Studio 15 2017 Win64"
> -DCMAKE_SYSTEM_VERSION=10.0.17134.0 -DENABLE_LIBEVENT=1
> -DHAS_AUTHENTICATION=0 -DPATCHEXE_PATH="C:\gnuwin32\bin" -T host=x64
> *Failures:*
> base64_tests.i
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(63): error C2664:
> 'std::string base64::encode_url_safe(const std::string &,bool)': cannot
> convert argument 1 from 'const char8_t [12]' to 'const std::string &'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(63): note: Reason: cannot
> convert from 'const char8_t [12]' to 'const std::string'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(63): note: No constructor
> could take the source type, or constructor overload resolution was ambiguous
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(63): error C2660:
> 'testing::internal::EqHelper<false>::Compare': function does not take 3
> arguments
>
> D:\Mesos\build_x64\3rdparty\googletest-1.8.0\src\googletest-1.8.0\googletest\include\gtest/gtest.h(1430):
> note: see declaration of 'testing::internal::EqHelper<false>::Compare'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(63): error C2512:
> 'testing::AssertionResult': no appropriate default constructor available
>
> D:\Mesos\build_x64\3rdparty\googletest-1.8.0\src\googletest-1.8.0\googletest\include\gtest/gtest.h(256):
> note: see declaration of 'testing::AssertionResult'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(67): error C2664:
> 'std::string base64::encode_url_safe(const std::string &,bool)': cannot
> convert argument 1 from 'const char8_t [12]' to 'const std::string &'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(67): note: Reason: cannot
> convert from 'const char8_t [12]' to 'const std::string'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(67): note: No constructor
> could take the source type, or constructor overload resolution was ambiguous
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(67): error C2660:
> 'testing::internal::EqHelper<false>::Compare': function does not take 3
> arguments
>
> D:\Mesos\build_x64\3rdparty\googletest-1.8.0\src\googletest-1.8.0\googletest\include\gtest/gtest.h(1430):
> note: see declaration of 'testing::internal::EqHelper<false>::Compare'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(67): error C2512:
> 'testing::AssertionResult': no appropriate default constructor available
>
> D:\Mesos\build_x64\3rdparty\googletest-1.8.0\src\googletest-1.8.0\googletest\include\gtest/gtest.h(256):
> note: see declaration of 'testing::AssertionResult'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(83): error C2664:
> 'Try<std::string,Error> base64::decode_url_safe(const std::string &)': cannot
> convert argument 1 from 'const char8_t [16]' to 'const std::string &'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(83): note: Reason: cannot
> convert from 'const char8_t [16]' to 'const std::string'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(83): note: No constructor
> could take the source type, or constructor overload resolution was ambiguous
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(83): error C2672:
> 'AssertSomeEq': no matching overloaded function found
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(83): error C2780:
> 'testing::AssertionResult AssertSomeEq(const char *,const char *,const T1
> &,const T2 &)': expects 4 arguments - 3 provided
> D:\Mesos\src\3rdparty\stout\include\stout/gtest.hpp(79): note: see
> declaration of 'AssertSomeEq'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(83): error C2512:
> 'testing::AssertionResult': no appropriate default constructor available
>
> D:\Mesos\build_x64\3rdparty\googletest-1.8.0\src\googletest-1.8.0\googletest\include\gtest/gtest.h(256):
> note: see declaration of 'testing::AssertionResult'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(87): error C2664:
> 'Try<std::string,Error> base64::decode_url_safe(const std::string &)': cannot
> convert argument 1 from 'const char8_t [17]' to 'const std::string &'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(87): note: Reason: cannot
> convert from 'const char8_t [17]' to 'const std::string'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(87): note: No constructor
> could take the source type, or constructor overload resolution was ambiguous
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(87): error C2672:
> 'AssertSomeEq': no matching overloaded function found
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(87): error C2780:
> 'testing::AssertionResult AssertSomeEq(const char *,const char *,const T1
> &,const T2 &)': expects 4 arguments - 3 provided
> D:\Mesos\src\3rdparty\stout\include\stout/gtest.hpp(79): note: see
> declaration of 'AssertSomeEq'
> D:\Mesos\src\3rdparty\stout\tests\base64_tests.cpp(87): error C2512:
> 'testing::AssertionResult': no appropriate default constructor available
>
> D:\Mesos\build_x64\3rdparty\googletest-1.8.0\src\googletest-1.8.0\googletest\include\gtest/gtest.h(256):
> note: see declaration of 'testing::AssertionResult'
>
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