export AD                    # Used in front of Makefile lines to suppress the printing of the command if user did not opt-in to see them.
  export QUIET                 # The parameter to use whether to show verbose makefile commands or not.
  
  export APPLICATION           # The application, set in the Makefile which is run by the user.
  export BOARD                 # The board to compile the application for.
  export CPU                   # The CPU, set by the board's Makefile.include.
  export CPU_MODEL             # The specific identifier of the used CPU, used for some CPU implementations to differentiate between different memory layouts
  export MCU                   # The MCU, set by the board's Makefile.include, or defaulted to the same value as CPU.
  export INCLUDES              # The extra include paths, set by the various Makefile.include files.
  
  export USEMODULE             # Sys Module dependencies of the application. Set in the application's Makefile.
  export USEPKG                # Pkg dependencies (third party modules) of the application. Set in the application's Makefile.
  export DISABLE_MODULE        # Used in the application's Makefile to suppress DEFAULT_MODULEs.
  export APPDEPS               # Files / Makefile targets that need to be created before the application can be build. Set in the application's Makefile.
  
  export RIOTBASE              # The root folder of RIOT. The folder where this very file lives in.
  export RIOTCPU               # For third party CPUs this folder is the base of the CPUs.
  export RIOTBOARD             # For third party BOARDs this folder is the base of the BOARDs.
  export RIOTPKG               # For overriding RIOT's pkg directory
  export RIOTPROJECT           # Top level git root of the project being built, or PWD if not a git repository
  export BINDIRBASE            # This is the folder where the application should be built in. For each BOARD a different subfolder is used.
  export BINDIR                # This is the folder where the application should be built in.
  export APPDIR                # The base folder containing the application
  
  export TARGET_ARCH           # The target platform name, in GCC triple notation, e.g. "arm-none-eabi", "i686-elf", "avr"
  export PREFIX                # The prefix of the toolchain commands, usually "$(TARGET_ARCH)-", e.g. "arm-none-eabi-" or "msp430-".
  export CC                    # The C compiler to use.
  export CXX                   # The CXX compiler to use.
  export CFLAGS                # The compiler flags. Must only ever be used with `+=`.
  export CXXUWFLAGS            # (Patters of) flags in CFLAGS, that should not be passed to CXX.
  export CXXEXFLAGS            # Additional flags that should be passed to CXX.
  export AR                    # The command to create the object file archives.
  export ARFLAGS               # Command-line options to pass to AR, default `rcs`.
  export AS                    # The assembler.
  export ASFLAGS               # Flags for the assembler.
  export LINK                  # The command used to link the files. Must take the same parameters as GCC, i.e. "ld" won't work.
  export LINKFLAGS             # Flags to supply in the linking step.
  export LTOFLAGS              # extra CFLAGS for compiling with link time optimization
  export OBJCOPY               # The command used to create the HEXFILE.
  export OFLAGS                # The parameter for OBJCOPY, e.g. to strip the debug information.
  export OBJDUMP               # The command used to create the assembly listing.
  export OBJDUMPFLAGS          # The parameter for OBJDUMP.
  export SIZE                  # The command to read to size of the ELF sections.
  export UNDEF                 # Set by the BOARD's and CPU's Makefile.include, this contains object files with must not be used in the ELFFILE even if the if no call to the functions.
  export WERROR                # Treat all compiler warnings as errors if set to 1 (see -Werror flag in GCC manual)
  
  export GITCACHE              # path to git-cache executable
  export FLASHER               # The command to call on "make flash".
  export FFLAGS                # The parameters to supply to FLASHER.
  export TERMPROG              # The command to call on "make term".
  export TERMFLAGS             # Additional parameters to supply to TERMPROG.
  export PORT                  # The port to connect the TERMPROG to.
  export ELFFILE               # The unstripped result of the compilation.
  export HEXFILE               # The stripped result of the compilation.
  export DEBUGGER              # The command to call on "make debug", usually a script starting the GDB front-end.
  export DEBUGGER_FLAGS        # The parameters to supply to DEBUGGER.
  export DEBUGSERVER           # The command to call on "make debug-server", usually a script starting the GDB server.
  export DEBUGSERVER_FLAGS     # The parameters to supply to DEBUGSERVER.
  export RESET                 # The command to call on "make reset", this command resets/reboots the target.
  export RESET_FLAGS           # The parameters to supply to RESET.
  
  export CCACHE_BASEDIR        # ccache basedir, allows multiple riot build
                               # directories to share a ccache directory
  
  export DOWNLOAD_TO_FILE      # Use `$(DOWNLOAD_TO_FILE) $(DESTINATION) $(URL)` to download `$(URL)` to `$(DESTINATION)`.
  export DOWNLOAD_TO_STDOUT    # Use `$(DOWNLOAD_TO_STDOUT) $(URL)` to download `$(URL)` output `$(URL)` to stdout, e.g. to be piped into `tar xz`.
  export UNZIP_HERE            # Use `cd $(SOME_FOLDER) && $(UNZIP_HERE) $(SOME_FILE)` to extract the contents of the zip file `$(SOME_FILE)` into `$(SOME_FOLDER)`.