How to determine host value for configure when using cross compiler

General question: If I use a cross compiler, how can I tell the value of the "--host" option I should give when I run configure?

Specific: I'm using cross compiler for arm64 arch. What is the correct "--host" value to use?

If I use a cross compiler, how can I tell the value of the --host option I should give when I run ./configure?

Three machines must be distinguished when discussing toolchain creation

• The build machine, where the toolchain is built.
• The host machine, where the toolchain will be executed.
• The target machine, where the binaries created by the toolchain are executed.

Four common build types are possible for toolchains are:

• Native build i.e. BUILD==HOST==TARGET
  Used to build normal gcc for workstation. e.g. BUILD==HOST==TARGET==x86

• Cross-build i.e. BUILD==HOST!=TARGET
  Used to build toolchain that works on your workstation but generates binary for target. e.g. BUILD==HOST==x86 TARGET==arm

• Cross-native build i.e. BUILD!=HOST==TARGET
  Used to toolchain that works on your target and generates binary for target. e.g BUILD==x86 HOST==TARGET==ARM

• Canadian toolchain i.e. BUILD!=HOST!=TARGET
  Used to build ARCHITECTURE A a toolchain runs on B and generates binary for architecture C. e.g.BUILD==x86 HOST==mac TARGET==arm

With armed this basics coming to your question.

For any software, first run ./configure --help

Host type:

--build=BUILD           configure for building on BUILD [BUILD=HOST]
--host=HOST             configure for HOST [guessed]
--target=TARGET         configure for TARGET [TARGET=HOST]

You will find above so depending on what you want to do, you need to set it for cross compiling. If all options are available, then you want to execute on arm target then set --host={your toolchain triplet} --target={your toolchain triplet}.

For example, if you are using arm-none-linux-gnueabi-gcc, set --host=arm-none-linux-gnueabi --target=arm-none-linux-gnueabi. This will write to your makefile. Finally, generated executable will run on target. For --build this will be automatically set, no need to worry.

For some software package only two option available i.e host and build. here if set host is enough to cross-compile

Specific: I'm using cross compiler for arm64 arch. What is the correct --host value to use?

For x86_64, --host={triplet} is generally given, so I think the same should work for arm64 by setting --host={triplet} for your toolchain, but I'm not sure.

The easiest way to find out what to input in --host, is by running config.guess on the host machine. On my machine it was located in /usr/share/automake-1.15/ , but I recommend running locate config.guess to find it.

The script is open source (GPL) and available at this address in case it is not available on your machine:

https://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess

On my target machine, a tegra X1 (also an aarch64) the answer it gave was aarch64-unknown-linux-gnu, which seems to work fine for cross-compiling.

--host is the "triplet" for the machine on which your resultant build will ultimately run. In your case "arm64" is the architecture, but it is only one piece of the triplet. In any event it maps to the string "aarch64" in the triplet. One possible value is

--host=aarch64-linux-android

this page from gnu.org gives the definitive answer about --host/--target/--build usage