u8path<std::string> deprecation with libc++ and c++20

Sjors commented at 9:25 am on March 26, 2022: member

When trying to compile with c++20 support (added in #24169) on macOS 12.3 on master I get inundated with the below warning.

0 ./configure --enable-c++20 --enable-suppress-external-warnings

 0In file included from bitcoin-cli.cpp:19:
 1In file included from ./util/system.h:20:
 2./fs.h:71:29: warning: 'u8path<std::string>' is deprecated [-Wdeprecated-declarations]
 3    return std::filesystem::u8path(utf8_str);
 4                            ^
 5/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/filesystem:1570:27: note: 'u8path<std::string>' has been explicitly marked deprecated here
 6_LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_WITH_CHAR8_T
 7                          ^
 8/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/__config:1078:43: note: expanded from macro '_LIBCPP_DEPRECATED_WITH_CHAR8_T'
 9#  define _LIBCPP_DEPRECATED_WITH_CHAR8_T _LIBCPP_DEPRECATED
10                                          ^
11/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/c++/v1/__config:1043:48: note: expanded from macro '_LIBCPP_DEPRECATED'
12#    define _LIBCPP_DEPRECATED __attribute__ ((deprecated))
13                                               ^
141 warning generated.

Sjors added the label Bug on Mar 26, 2022

MarcoFalke commented at 9:43 am on March 26, 2022: member

On Windows there is _SILENCE_CXX20_U8PATH_DEPRECATION_WARNING, maybe something similar exists for macOS?

An alternative would be to copy the string into a std::u8string first: return std::filesystem::u8path(std::u8string{utf8_str.begin(), utf8_str.end()}); (obviously guarded by C++20)

bitcoin deleted a comment on Mar 27, 2022

laanwj commented at 12:59 pm on April 5, 2022: member

0#define string u8string

:sweat_smile:

fanquake removed the label Bug on Aug 8, 2022

fanquake renamed this:
~~u8path<std::string> deprecation on macOS with c++20~~
u8path<std::string> deprecation with libc++ and c++20
on Aug 8, 2022

fanquake commented at 4:03 pm on August 8, 2022: member

This isn’t macOS specific or a bug, so I’ve updated the title and labels. It’s going to occur when using c++20 and libc++, and does so building with Clang and libc++ on Linux. i.e:

0clang --version
1Ubuntu clang version 14.0.0-1ubuntu1
2Target: x86_64-pc-linux-gnu
3Thread model: posix
4InstalledDir: /usr/bin

 0./autogen.sh
 1CC='clang' CXX='clang++ -stdlib=libc++' ./configure --enable-c++20
 2make
 3...
 4  CXX      bitcoind-bitcoind.o
 5In file included from bitcoind.cpp:14:
 6In file included from ./interfaces/chain.h:9:
 7In file included from ./util/settings.h:8:
 8./fs.h:72:29: warning: 'u8path<std::string>' is deprecated [-Wdeprecated-declarations]
 9    return std::filesystem::u8path(utf8_str);
10                            ^
11/usr/lib/llvm-14/bin/../include/c++/v1/__filesystem/u8path.h:72:27: note: 'u8path<std::string>' has been explicitly marked deprecated here
12_LIBCPP_INLINE_VISIBILITY _LIBCPP_DEPRECATED_WITH_CHAR8_T
13                          ^
14/usr/lib/llvm-14/bin/../include/c++/v1/__config:1042:43: note: expanded from macro '_LIBCPP_DEPRECATED_WITH_CHAR8_T'
15#  define _LIBCPP_DEPRECATED_WITH_CHAR8_T _LIBCPP_DEPRECATED
16                                          ^
17/usr/lib/llvm-14/bin/../include/c++/v1/__config:1007:48: note: expanded from macro '_LIBCPP_DEPRECATED'
18#    define _LIBCPP_DEPRECATED __attribute__ ((deprecated))
19                                               ^
201 warning generated.

We could suppress all deprecated-declaration warnings when building with c++20, but that’d be overkill. We can probably just pragma around the single instance in our code we want to suppress, and let any other deprecation warnings bubble up.

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u8pathstd::string deprecation with libc++ and c++20 #24682