How to install watchman on Ubuntu 18.04, for react-native? error in make command

ref. https://facebook.github.io/watchman/docs/install.html#installing-from-source

git clone https://github.com/facebook/watchman.git
cd watchman/
git checkout v4.9.0
sudo apt-get install -y autoconf automake build-essential python-dev libssl-dev libtool
./autogen.sh
./configure
make
sudo make install

Make sure to run git checkout v4.9.0. That is, check out v4.9.0, not v4.7.

Watchman is available in Debian sid and Ubuntu 20.04 and can be installed with:

# apt-get install watchman

Watchman version 4.7.0 isn't compatible with GCC 7.x, as reported here:
https://github.com/facebook/watchman/issues/467

Note, Ubuntu 18.04 ships with GCC 7.3.

Try building the latest version, v4.9.0, in which the issue is fixed:
https://github.com/facebook/watchman/releases/tag/v4.9.0

Alternatively, use an earlier GCC version for building Watchman, such as 5.4.