Add support for parsing cpu-vendor-os target triplets

1 files changed, 97 insertions, 0 deletions

diff --git a/butl/triplet b/butl/triplet
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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