error: no template named 'remove_cv_t' in namespace 'std'; did you mean 'remove_cv'?

Question

My problem seems similar to this issue, except it happens when I run yarn install in a rails app.

When I run yarn install, it runs successfully for some time, then

../src/libsass/src/ast.hpp:1614:25: warning: loop variable 'numerator' of type 'const std::__1::basic_string<char>' creates a copy from type 'const std::__1::basic_string<char>' [-Wrange-loop-analysis]         for (const auto numerator : numerators)                         ^ ../src/libsass/src/ast.hpp:1614:14: note: use reference type 'const std::__1::basic_string<char> &' to prevent copying         for (const auto numerator : numerators)              ^~~~~~~~~~~~~~~~~~~~~~                         & ../src/libsass/src/ast.hpp:1616:25: warning: loop variable 'denominator' of type 'const std::__1::basic_string<char>' creates a copy from type 'const std::__1::basic_string<char>' [-Wrange-loop-analysis]         for (const auto denominator : denominators)                         ^ ../src/libsass/src/ast.hpp:1616:14: note: use reference type 'const std::__1::basic_string<char> &' to prevent copying         for (const auto denominator : denominators)              ^~~~~~~~~~~~~~~~~~~~~~~~                         & 2 warnings generated.   rm -f Release/sass.a && ./gyp-mac-tool filter-libtool libtool  -static -o Release/sass.a Release/obj.target/libsass/src/libsass/src/ast.o Release/obj.target/libsass/src/libsass/src/ast_fwd_decl.o Release/obj.target/libsass/src/libsass/src/backtrace.o Release/obj.target/libsass/src/libsass/src/base64vlq.o Release/obj.target/libsass/src/libsass/src/bind.o Release/obj.target/libsass/src/libsass/src/cencode.o Release/obj.target/libsass/src/libsass/src/check_nesting.o Release/obj.target/libsass/src/libsass/src/color_maps.o Release/obj.target/libsass/src/libsass/src/constants.o Release/obj.target/libsass/src/libsass/src/context.o Release/obj.target/libsass/src/libsass/src/cssize.o Release/obj.target/libsass/src/libsass/src/emitter.o Release/obj.target/libsass/src/libsass/src/environment.o Release/obj.target/libsass/src/libsass/src/error_handling.o Release/obj.target/libsass/src/libsass/src/eval.o Release/obj.target/libsass/src/libsass/src/expand.o Release/obj.target/libsass/src/libsass/src/extend.o Release/obj.target/libsass/src/libsass/src/file.o Release/obj.target/libsass/src/libsass/src/functions.o Release/obj.target/libsass/src/libsass/src/inspect.o Release/obj.target/libsass/src/libsass/src/json.o Release/obj.target/libsass/src/libsass/src/lexer.o Release/obj.target/libsass/src/libsass/src/listize.o Release/obj.target/libsass/src/libsass/src/memory/SharedPtr.o Release/obj.target/libsass/src/libsass/src/node.o Release/obj.target/libsass/src/libsass/src/operators.o Release/obj.target/libsass/src/libsass/src/output.o Release/obj.target/libsass/src/libsass/src/parser.o Release/obj.target/libsass/src/libsass/src/plugins.o Release/obj.target/libsass/src/libsass/src/position.o Release/obj.target/libsass/src/libsass/src/prelexer.o Release/obj.target/libsass/src/libsass/src/remove_placeholders.o Release/obj.target/libsass/src/libsass/src/sass.o Release/obj.target/libsass/src/libsass/src/sass2scss.o Release/obj.target/libsass/src/libsass/src/sass_context.o Release/obj.target/libsass/src/libsass/src/sass_functions.o Release/obj.target/libsass/src/libsass/src/sass_util.o Release/obj.target/libsass/src/libsass/src/sass_values.o Release/obj.target/libsass/src/libsass/src/source_map.o Release/obj.target/libsass/src/libsass/src/subset_map.o Release/obj.target/libsass/src/libsass/src/to_c.o Release/obj.target/libsass/src/libsass/src/to_value.o Release/obj.target/libsass/src/libsass/src/units.o Release/obj.target/libsass/src/libsass/src/utf8_string.o Release/obj.target/libsass/src/libsass/src/util.o Release/obj.target/libsass/src/libsass/src/values.o   c++ '-DNODE_GYP_MODULE_NAME=binding' '-DUSING_UV_SHARED=1' '-DUSING_V8_SHARED=1' '-DV8_DEPRECATION_WARNINGS=1' '-DV8_DEPRECATION_WARNINGS' '-DV8_IMMINENT_DEPRECATION_WARNINGS' '-D_GLIBCXX_USE_CXX11_ABI=1' '-D_DARWIN_USE_64_BIT_INODE=1' '-D_LARGEFILE_SOURCE' '-D_FILE_OFFSET_BITS=64' '-DBUILDING_NODE_EXTENSION' -I/Users/st/.node-gyp/16.0.0/include/node -I/Users/st/.node-gyp/16.0.0/src -I/Users/st/.node-gyp/16.0.0/deps/openssl/config -I/Users/st/.node-gyp/16.0.0/deps/openssl/openssl/include -I/Users/st/.node-gyp/16.0.0/deps/uv/include -I/Users/st/.node-gyp/16.0.0/deps/zlib -I/Users/st/.node-gyp/16.0.0/deps/v8/include -I../../nan -I../src/libsass/include  -O3 -gdwarf-2 -mmacosx-version-min=10.7 -arch x86_64 -Wall -Wendif-labels -W -Wno-unused-parameter -std=c++11 -stdlib=libc++ -fno-rtti -fno-exceptions -fno-strict-aliasing -MMD -MF ./Release/.deps/Release/obj.target/binding/src/binding.o.d.raw   -c -o Release/obj.target/binding/src/binding.o ../src/binding.cpp In file included from ../src/binding.cpp:1: In file included from ../../nan/nan.h:56: In file included from /Users/st/.node-gyp/16.0.0/include/node/node.h:63: In file included from /Users/st/.node-gyp/16.0.0/include/node/v8.h:30: /Users/st/.node-gyp/16.0.0/include/node/v8-internal.h:452:38: error: no template named 'remove_cv_t' in namespace 'std'; did you mean 'remove_cv'?             !std::is_same<Data, std::remove_cv_t<T>>::value>::Perform(data);                                 ~~~~~^~~~~~~~~~~                                      remove_cv /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/../include/c++/v1/type_traits:697:50: note: 'remove_cv' declared here template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_cv                                                  ^ 1 error generated. make: *** [Release/obj.target/binding/src/binding.o] Error 1 gyp ERR! build error  gyp ERR! stack Error: `make` failed with exit code: 2 gyp ERR! stack     at ChildProcess.onExit (/Users/st/rails/myapp/node_modules/node-gyp/lib/build.js:262:23) gyp ERR! stack     at ChildProcess.emit (node:events:365:28) gyp ERR! stack     at Process.ChildProcess._handle.onexit (node:internal/child_process:290:12) gyp ERR! System Darwin 20.3.0 gyp ERR! command "/usr/local/Cellar/node/16.0.0/bin/node" "/Users/st/rails/myapp/node_modules/node-gyp/bin/node-gyp.js" "rebuild" "--verbose" "--libsass_ext=" "--libsass_cflags=" "--libsass_ldflags=" "--libsass_library=" gyp ERR! cwd /Users/st/rails/myapp/node_modules/node-sass gyp ERR! node -v v16.0.0 gyp ERR! node-gyp -v v3.8.0 gyp ERR! not ok  

Any ideas how to solve this? (I'm not even sure if it's a problem with xcode/node/rails/c++)

Other notes

• /usr/bin/xcodebuild -version returns

Xcode 12.4 Build version 12D4e 

• cpp --version returns

Apple clang version 12.0.0 (clang-1200.0.32.29) Target: x86_64-apple-darwin20.3.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin 

Please note: I don't code in cpp, so I have very little contextual knowledge of how to solve.

Answer 1

Update: Since node-sass version 6.0.1, Node 16 is supported. Updating node-sass to a version higher than 6.0.1 solves this issue.

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What you're seeing is an error during compilation of node-sass. That's a package processing your Sass/SCSS styles, which is written in C++ and only re-packaged as a JavaScript library. The fact it's written in C++ means it needs to be compiled on your device during installation (this is internally done by a tool called node-gyp, which you can spot in your error output, too).

The problem is node-sass doesn't support Node 16 as of writing this answer, see tracking issue: https://github.com/sass/node-sass/issues/3077 There's no estimate on when it's gonna support it (and that's fair, as it's a volunteer-driven project). Even if you manage to install node-sass on Node 16, I'd advice against it, as the behavior might be undefined.

The correct solution is to downgrade your Node installation to a supported version (I can see both 14 and 15 tested in their CI). If you git cloned a project and it won't install on your machine, but works for your colleagues or on the production server, it's likely the project has a different version of Node in mind too, and isn't tested on Node 16, so I'd advice against developing it on Node 16 anyway. If the project worked for you just a few days ago, but it doesn't work now, it's very likely you recently upgraded your system setup (e.g. Homebrew), which upgraded you to Node 16 (this is what happened to me and how I found this question).

You should check with the authors of the project what's the production server version of Node it runs on and install that version locally, too. As a best practice, in the future, keep the production version and your local version of Node (and yarn or npm) in sync. For managing multiple Node versions, you can use this tool https://github.com/nvm-sh/nvm

Answer 2

Update - simple fix!

Here's an easy way to solve this that lets you keep using node 16.

1. Delete yarn.lock
2. Open package.json and make sure you use webpacker version 5.4.3 (which is the latest version - it won't pull in the old version of node-sass that causes this problem)
3. Run yarn install
4. Start your rails server and everything should be back to normal!

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Here is the previous, much longer answer (in case it's still useful):

node-sass is not yet compatible with node v16

To get around this, downgrade node (e.g. to version 14) until node-sass is compatible with v16. To downgrade node using nvm, simply run:

nvm install 14 

Set version 14 globally (so each new terminal windows defaults to node version 14) by running:

nvm alias default 14 

Now you have node 14 installed and set as default! ..now you just need to make your app use v14.

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How to make your rails app use node 14

Install node 14 (see above). Open terminal and head to your app's root directory, then:

1. Stop your rails server if it's running
2. Open a fresh new terminal window (so that node --version returns 14.x (not 16)
3. Run spring stop
4. Delete yarn.lock
5. Remove existing node modules with rm -rf node_modules
6. Check that node --version returns 14. If it doesn't run nvm install 14 again.
7. Now reinstall modules with yarn install (if you don't have yarn for node 14, install it with npm install --global yarn)
8. It should succeed!
9. Restart your rails server, and it will work!

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If you have this problem specifically on heroku, try also ensuring your webpacker is up to date:

yarn upgrade @rails/webpacker --latest