From fac576a331d6587e4343d09d6caf959d9a776118 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 11 Jul 2016 05:56:17 +0200
Subject: Add bin.ld sub-module

---
 build2/bin/guess.cxx | 120 +++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 116 insertions(+), 4 deletions(-)

(limited to 'build2/bin/guess.cxx')

diff --git a/build2/bin/guess.cxx b/build2/bin/guess.cxx
index d036f81..ea4ac49 100644
--- a/build2/bin/guess.cxx
+++ b/build2/bin/guess.cxx
@@ -22,10 +22,10 @@ namespace build2
       empty () const {return id.empty ();}
     };
 
-    bin_info
-    guess (const path& ar, const path& rl)
+    ar_info
+    guess_ar (const path& ar, const path& rl)
     {
-      tracer trace ("bin::guess");
+      tracer trace ("bin::guess_ar");
 
       guess_result arr, rlr;
 
@@ -166,9 +166,121 @@ namespace build2
           fail << "unable to guess " << rl << " signature";
       }
 
-      return bin_info {
+      return ar_info {
         move (arr.id), move (arr.signature), move (arr.checksum),
         move (rlr.id), move (rlr.signature), move (rlr.checksum)};
     }
+
+    ld_info
+    guess_ld (const path& ld)
+    {
+      tracer trace ("bin::guess_ld");
+
+      guess_result r;
+
+      // Binutils ld recognizes the --version option. Microsoft's link.exe
+      // doesn't support --version (nor any other way to get the version
+      // without the error exist status) but it will still print its banner.
+      // We also want to recognize link.exe as fast as possible since it will
+      // be the most commonly configured linker (for other platoforms the
+      // linker will normally be used indirectly via the compiler and the
+      // bin.ld module won't be loaded). So we are going to ignore the error
+      // exit status. Our signatures are fairly specific to avoid any kind
+      // of false positives.
+      //
+      {
+        auto f = [] (string& l) -> guess_result
+        {
+          // Microsoft link.exe output starts with "Microsoft (R) ".
+          //
+          if (l.compare (0, 14, "Microsoft (R) ") == 0)
+            return guess_result {"msvc", move (l), ""};
+
+          // Binutils ld.bfd --version output has a line that starts with
+          // "GNU ld " while ld.gold -- "GNU gold".
+          //
+          if (l.compare (0, 7, "GNU ld ") == 0)
+            return guess_result {"gnu", move (l), ""};
+
+          if (l.compare (0, 9, "GNU gold ") == 0)
+            return guess_result {"gold", move (l), ""};
+
+          return guess_result ();
+        };
+
+        // Redirect STDERR to STDOUT and ignore exit status. Note that in case
+        // of link.exe we will hash the diagnostics (yes, it goes to stdout)
+        // but that seems harmless.
+        //
+        sha256 cs;
+        r = run<guess_result> (ld, "--version", f, false, true, &cs);
+
+        if (!r.empty ())
+          r.checksum = cs.string ();
+      }
+
+      // Next try -v which will cover Apple's linkers.
+      //
+      if (r.empty ())
+      {
+        auto f = [] (string& l) -> guess_result
+        {
+          // New ld64 has "PROJECT:ld64" in the first line (output to stderr),
+          // for example:
+          //
+          // @(#)PROGRAM:ld  PROJECT:ld64-242.2
+          //
+          if (l.find ("PROJECT:ld64") != string::npos)
+            return guess_result {"ld64", move (l), ""};
+
+          // Old ld has "cctools" in the first line, for example:
+          //
+          // Apple Computer, Inc. version cctools-622.9~2
+          //
+          if (l.find ("cctools") != string::npos)
+            return guess_result {"cctools", move (l), ""};
+
+          return guess_result ();
+        };
+
+        sha256 cs;
+        r = run<guess_result> (ld, "-v", f, false, false, &cs);
+
+        if (!r.empty ())
+          r.checksum = cs.string ();
+      }
+
+      // Finally try -version which will take care of LLVM's lld.
+      //
+      if (r.empty ())
+      {
+        auto f = [] (string& l) -> guess_result
+        {
+          // Unlike other LLVM tools (e.g., ar), the lld's version is printed
+          // (to stderr) as:
+          //
+          // LLVM Linker Version: 3.7
+          //
+          if (l.compare (0, 19, "LLVM Linker Version") == 0)
+            return guess_result {"llvm", move (l), ""};
+
+          return guess_result ();
+        };
+
+        // Suppress all the errors because we may be trying an unsupported
+        // option.
+        //
+        sha256 cs;
+        r = run<guess_result> (ld, "-version", f, false, false, &cs);
+
+        if (!r.empty ())
+          r.checksum = cs.string ();
+      }
+
+      if (r.empty ())
+        fail << "unable to guess " << ld << " signature";
+
+      return ld_info {move (r.id), move (r.signature), move (r.checksum)};
+    }
   }
 }
-- 
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