Setting up a STM32 toolchain can be confusing. Here is how i do it.

macOS

1. If you have not installed Homebrew yet, you should do that right now.

2. Install stlink:

   brew install stlink
   

3. Install GNU ARM GCC Toolchain:

   xcode-select --install
   brew tap PX4/homebrew-px4
   brew update
   brew install genromfs
   brew install gcc-arm-none-eabi
   

4. Install eclipse:

   brew tap caskroom/cask
   brew cask install java
   brew cask install eclipse-cpp
   

5. Install the GNU ARM Eclipse Plugin.

   In Project Properties -> C/C++ Build -> Environment -> Add:

   Name: PATH Value: /usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

6. Setting up a debug configuration source:

   Simply follow the onsite instructions

Windows

1. The ugly things first.. install Java.

2. Next, install eclipse.

3. Install the Windows Build Tools for GNU ARM development.

4. Install the GNU ARM Eclipse Plugin.

5. Setting up a debug configuration source:

   Simply follow the onsite instructions. Use a current windows build from the stlink release site.