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| -rw-r--r-- | part3intro/toolchaintechnotes.xml | 31 |
1 files changed, 22 insertions, 9 deletions
diff --git a/part3intro/toolchaintechnotes.xml b/part3intro/toolchaintechnotes.xml index 49656d052..7a8058424 100644 --- a/part3intro/toolchaintechnotes.xml +++ b/part3intro/toolchaintechnotes.xml @@ -145,15 +145,28 @@ <title>Implementation of Cross-Compilation for LFS</title> <note> - <para>Almost all the build systems use names of the form - cpu-vendor-kernel-os, referred to as the machine triplet. (Sometimes, - the vendor field is omitted.) An astute - reader may wonder why a <quote>triplet</quote> refers to a four component - name. The reason is historical: initially, three component names were enough - to designate a machine unambiguously, but as new machines and systems - proliferated, that proved insufficient. The word <quote>triplet</quote> - remained. A simple way to determine your machine triplet is to run - the <command>config.guess</command> + <para>All packages involved with cross compilation in the book use an + autoconf-based building system. The autoconf-based building system + accepts system types in the form cpu-vendor-kernel-os, + referred to as the system triplet. Since the vendor field is mostly + irrelevant, autoconf allows to omit it. An astute reader may wonder + why a <quote>triplet</quote> refers to a four component name. The + reason is the kernel field and the os field originiated from one + <quote>system</quote> field. Such a three-field form is still valid + today for some systems, for example + <literal>x86_64-unknown-freebsd</literal>. But for other systems, + two systems can share the same kernel but still be too different to + use a same triplet for them. For example, an Android running on a + mobile phone is completely different from Ubuntu running on an ARM64 + server. Without an emulation layer, you cannot run an executable for + the server on the mobile phone or vice versa. So the + <quote>system</quote> field is separated into kernel and os fields to + designate these systems unambiguously. For our example, the Android + system is designated <literal>aarch64-unknown-linux-android</literal>, + and the Ubuntu system is designated + <literal>aarch64-unknown-linux-gnu</literal>. The word + <quote>triplet</quote> remained. A simple way to determine your + system triplet is to run the <command>config.guess</command> script that comes with the source for many packages. Unpack the binutils sources and run the script: <userinput>./config.guess</userinput> and note the output. For example, for a 32-bit Intel processor the |