Because I want to use C++20 standard, I need to use GCC12, but the default compiler of Ubuntu20 is GCC9, so I have to compile and install a GCC trunk by myself.

I didn’t expect to have so many problems doing something that sounds so simple, so I’ll write a little bit of text to document it.

Download source code

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git clone https://github.com/gcc-mirror/gcc.git

Configure dependencies

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sudo apt install flex

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cd gcc
./contrib/download_prerequisites

Compile

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mkdir build && cd build

../configure -v --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --enable-checking=release --enable-languages=c,c++ --disable-multilib

make -j8

Wait patiently for the compilation to complete, depending on the performance of the machine.

Installation

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sudo make install

Problems encountered

After installing gcc, I don’t know why it reports an error when compiling LLVM.

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/lib/x86_64-linux-gnu/libstdc++.so.6: version `GLIBCXX_3.4.30' not found

Using strings /lib/x86_64-linux-gnu/libstdc++.so.6 | grep GLIBCXX you can see that there is indeed no GLIBCXX_3.4.30. Using ls -al /lib/x86_64-linux-gnu/libstdc++.so.6 you can see that this is a soft link

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lrwxrwxrwx 1 root root 36 1月   1 13:44 libstdc++.so.6 -> libstdc++.so.6.29

Obviously this is still an old version of libstdc++, and I’m not sure why it’s doing this -_-

The solution is straightforward, just re-link libstdc++.so.6 to our newly compiled version: libstdc++.so.6.

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unlink
ln -s /usr/local/lib64/libstdc++.so.6.0.30 /lib/x86_64-linux-gnu/libstdc++.so.6