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+// file : butl/triplet -*- C++ -*-
+// copyright : Copyright (c) 2014-2016 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_TRIPLET
+#define BUTL_TRIPLET
+
+#include <string>
+
+namespace butl
+{
+ // This is the ubiquitous 'target triplet' that loosely has the CPU-VENDOR-OS
+ // form which, these days, quite often takes the CPU-VENDOR-OS-ABI form. Plus
+ // some fields can sometimes be omitted. This looseness makes it hard to base
+ // any kind of decisions on the triplet without canonicalizing it and then
+ // splitting it into components. the way we are going to split it is like
+ // this:
+ //
+ // CPU
+ //
+ // This one is reasonably straightforward. Note that we always expect at
+ // least two components with the first being the CPU. In other words, we
+ // don't try to guess what just 'mingw32' might mean like config.sub does.
+ //
+ // VENDOR
+ //
+ // This can be a machine vendor as in i686-apple-darwin8, a toolchain vendor
+ // as in i686-lfs-linux-gnu, or something else as in arm-softfloat-linux-gnu.
+ // Just as we think vendor is pretty irrelevant and can be ignored, comes
+ // MinGW-W64 and calls itself *-w64-mingw32. While it is tempting to
+ // attribute w64 to OS-ABI, the MinGW-W64 folks insist it is a (presumably
+ // toolchain) vendor.
+ //
+ // To make thing more regular we also convert the information-free vendor
+ // names 'pc', 'unknown' and 'none' to the empty name.
+ //
+ // OS/KERNEL-OS/OS-ABI
+ //
+ // This is where things get really messy and instead of trying to guess, we
+ // call the entire thing SYSTEM. Except, in certain cases, we factor out the
+ // trailing version, again, to make SYSTEM easier to compare to. For example,
+ // *-darwin14.5.0 becomes 'darwin' and '14.5.0'.
+ //
+ // Again, to make things more regular, if the first component in SYSTEM is
+ // none, then it is removed (so *-none-eabi becomes just 'eabi').
+ //
+ // Values for two-component systems (e.g., linux-gnu) that don't specify
+ // VENDOR explicitly are inherently ambiguous: is 'linux' VENDOR or part of
+ // SYSTEM? The only way to handle this is to recognize their specific names
+ // as special cases and this is what we do for some of the more common
+ // ones. The alternative would be to first run such names through config.sub
+ // which adds explicit VENDOR and this could be a reasonable fallback
+ // strategy for (presumably less common) cases were we don't split things
+ // correctly.
+ //
+ // Note also that the version splitting is only done for certain,
+ // commonly-used targets.
+ //
+ // Some examples of canonicalization and splitting:
+ //
+ // x86_64-apple-darwin14.5.0 x86_64 apple darwin 14.5.0
+ // x86_64-unknown-freebsd10.2 x86_64 freebsd 10.2
+ // i686-elf i686 elf
+ // arm-eabi arm eabi
+ // arm-none-eabi arm eabi
+ // arm-none-linux-gnueabi arm linux-gnueabi
+ // arm-softfloat-linux-gnu arm softfloat linux-gnu
+ // i686-pc-mingw32 i686 mingw32
+ // i686-w64-mingw32 i686 w64 mingw32
+ // i686-lfs-linux-gnu i686 lfs linux-gnu
+ // x86_64-unknown-linux-gnu x86_64 linux-gnu
+ // x86_64-linux-gnux32 x86_64 linux-gnux32
+ //
+ // References:
+ //
+ // 1. The libtool repository contains the PLATFORM file that lists many known
+ // triplets.
+ //
+ // 2. LLVM has the Triple class with similar goals.
+ //
+ struct triplet
+ {
+ std::string cpu;
+ std::string vendor;
+ std::string system;
+ std::string version;
+
+ // Parse the triplet optionally returning the canonicalized string. Throw
+ // std::invalid_argument if the triplet is not recognizable.
+ //
+ explicit
+ triplet (const std::string&, std::string* canon = nullptr);
+ triplet (const std::string& s, std::string& canon): triplet (s, &canon) {}
+ };
+};
+
+#endif // BUTL_TRIPLET