# Upgrade libstdc++
###### tags: `Linux`

## Error
Vscode remote-ssh cannot connect to servers with CentOS 7.

## Reason
Vscode remote-ssh needs `glibc >=2.28, libstdc++ >= 3.4.25` ([source](https://code.visualstudio.com/docs/remote/linux)). We has previously upgraded the `glibc`, but for `libstdc++`, CentOS 7 only has `libstdc++.so.6.0.19` which supports up to `GLIBCXX_3.4.19`.

$ find /usr/ -name libstdc++.so.6*
/usr/lib64/libstdc++.so.6
/usr/lib64/libstdc++.so.6.0.19
/usr/share/gdb/auto-load/usr/lib64/libstdc++.so.6.0.19-gdb.py
/usr/share/gdb/auto-load/usr/lib64/libstdc++.so.6.0.19-gdb.pyc
/usr/share/gdb/auto-load/usr/lib64/libstdc++.so.6.0.19-gdb.pyo
/usr/local/cuda-12.3/nsight-compute-2023.3.0/host/linux-desktop-glibc_2_11_3-x64/libstdc++.so.6
/usr/local/cuda-12.3/nsight-systems-2023.3.3/host-linux-x64/libstdc++.so.6

$ ls -l /usr/lib64/libstdc++.so.6
lrwxrwxrwx. 1 root root 19 Mar 29  2023 /usr/lib64/libstdc++.so.6 -> libstdc++.so.6.0.19

$ strings /usr/lib64/libstdc++.so.6 | grep GLIBCXX
GLIBCXX_3.4
GLIBCXX_3.4.1
GLIBCXX_3.4.2
GLIBCXX_3.4.3
GLIBCXX_3.4.4
GLIBCXX_3.4.5
GLIBCXX_3.4.6
GLIBCXX_3.4.7
GLIBCXX_3.4.8
GLIBCXX_3.4.9
GLIBCXX_3.4.10
GLIBCXX_3.4.11
GLIBCXX_3.4.12
GLIBCXX_3.4.13
GLIBCXX_3.4.14
GLIBCXX_3.4.15
GLIBCXX_3.4.16
GLIBCXX_3.4.17
GLIBCXX_3.4.18
GLIBCXX_3.4.19
GLIBCXX_DEBUG_MESSAGE_LENGTH

Environment:
- OS: CentOS-7
- arch: x86_64

## Install libstdc++
Choose a version that matches our requirement from [here](http://ftp.gnu.org/gnu/gcc/). We need `GLIBCXX_3.4.25`, so `GCC` has to be higher than `8.1.0` (refer to this [website](https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html)).

wget http://ftp.gnu.org/gnu/gcc/gcc-8.5.0/gcc-8.5.0.tar.gz
tar -zxvf gcc-8.5.0.tar.gz
cd gcc-8.5.0
./contrib/download_prerequisites
mkdir build && cd build
../configure --enable-languages=c,c++ --disable-multilib
make -j4
make install

Check gain, we found that the symlink is not updated.

$ strings /usr/lib64/libstdc++.so.6 | grep GLIBCXX
...
GLIBCXX_3.4.19
GLIBCXX_DEBUG_MESSAGE_LENGTH

Update the symlink. (One can use `$ find /usr/ -name libstdc++.so.6*` to check what the new version is and where it is.)

cp /usr/local/lib64/libstdc++.so.6.0.25 /usr/lib64/
rm /usr/lib64/libstdc++.so.6
ln -sf libstdc++.so.6.0.24 /usr/lib64/libstdc++.so.6

---
Note that the installation changes `gcc`, which is upgraded from 8.3.1 to 8.5.0. (The path of `gcc` is changed from `/usr/bin/gcc` to `/usr/local/bin/gcc`.)

$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/8.5.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure --enable-languages=c,c++ --disable-multilib
Thread model: posix
gcc version 8.5.0 (GCC)

$ which gcc
/usr/local/bin/gcc

Original gcc is sill there.

$ /usr/bin/gcc -v
Using built-in specs.
COLLECT_GCC=/usr/bin/gcc
COLLECT_LTO_WRAPPER=/opt/rh/devtoolset-8/root/usr/libexec/gcc/x86_64-redhat-linux/8/lto-wrapper
Target: x86_64-redhat-linux
Configured with: ../configure --enable-bootstrap --enable-languages=c,c++,fortran,lto --prefix=/opt/rh/devtoolset-8/root/usr --mandir=/opt/rh/devtoolset-8/root/usr/share/man --infodir=/opt/rh/devtoolset-8/root/usr/share/info --with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-shared --enable-threads=posix --enable-checking=release --enable-multilib --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions --enable-gnu-unique-object --enable-linker-build-id --with-gcc-major-version-only --with-linker-hash-style=gnu --with-default-libstdcxx-abi=gcc4-compatible --enable-plugin --enable-initfini-array --with-isl=/builddir/build/BUILD/gcc-8.3.1-20190311/obj-x86_64-redhat-linux/isl-install --disable-libmpx --enable-gnu-indirect-function --with-tune=generic --with-arch_32=x86-64 --build=x86_64-redhat-linux
Thread model: posix
gcc version 8.3.1 20190311 (Red Hat 8.3.1-3) (GCC)

## Reference
1. https://blog.csdn.net/dm569263708/article/details/125198722

## Other Methods
1. Use `devtoolset`
https://blog.csdn.net/whatday/article/details/122081503
2. A good work that solves the issue easily
https://github.com/MikeWang000000/vscode-server-centos7/tree/master