From f4ed3e569cb5ebae855ea5309bfc17aa6b35874a Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 11 Dec 2014 07:35:54 +0200
Subject: Initial implementation of dependency injection (g++ -M output)

---
 build/cxx/rule     |   7 +++
 build/cxx/rule.cxx | 146 +++++++++++++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 150 insertions(+), 3 deletions(-)

(limited to 'build/cxx')

diff --git a/build/cxx/rule b/build/cxx/rule
index d4412e4..85352b7 100644
--- a/build/cxx/rule
+++ b/build/cxx/rule
@@ -6,6 +6,9 @@
 #define BUILD_CXX_RULE
 
 #include <build/rule>
+#include <build/native>
+
+#include <build/cxx/target>
 
 namespace build
 {
@@ -23,6 +26,10 @@ namespace build
 
       static target_state
       update (target&);
+
+    private:
+      bool
+      inject_prerequisites (obj&, const cxx&) const;
     };
 
     class link: public rule
diff --git a/build/cxx/rule.cxx b/build/cxx/rule.cxx
index 9f8f1ae..31c27dc 100644
--- a/build/cxx/rule.cxx
+++ b/build/cxx/rule.cxx
@@ -4,15 +4,17 @@
 
 #include <build/cxx/rule>
 
+#include <cstddef>  // size_t
+#include <cstdlib>  // exit
+#include <string>
 #include <vector>
 #include <iostream>
 
-#include <build/native>
+#include <ext/stdio_filebuf.h>
+
 #include <build/process>
 #include <build/timestamp>
 
-#include <build/cxx/target>
-
 using namespace std;
 
 namespace build
@@ -59,9 +61,147 @@ namespace build
       if (o.path ().empty ())
         o.path (path (o.name () + ".o"));
 
+      // Inject additional prerequisites.
+      //
+      // @@ If this failed, saying that the rule did not match is
+      //    not quite correct.
+      //
+      if (!inject_prerequisites (o, *s))
+        return recipe ();
+
       return recipe (&update);
     }
 
+    // Return the next make prerequisite starting from the specified
+    // position and update position to point to the start of the
+    // following prerequisite or l.size() if there are none left.
+    //
+    static string
+    next (const string& l, size_t& p)
+    {
+      size_t n (l.size ());
+
+      // Skip leading spaces.
+      //
+      for (; p != n && l[p] == ' '; p++) ;
+
+      // Lines containing multiple prerequisites are 80 characters max.
+      //
+      string r;
+      r.reserve (n);
+
+      // Scan the next prerequisite while watching out for escape sequences.
+      //
+      for (; p != n && l[p] != ' '; p++)
+      {
+        char c (l[p]);
+
+        if (c == '\\')
+          c = l[++p];
+
+        r += c;
+      }
+
+      // Skip trailing spaces.
+      //
+      for (; p != n && l[p] == ' '; p++) ;
+
+      // Skip final '\'.
+      //
+      if (p == n - 1 && l[p] == '\\')
+        p++;
+
+      return r;
+    }
+
+    bool compile::
+    inject_prerequisites (obj& o, const cxx& s) const
+    {
+      const char* args[] = {
+        "g++-4.9",
+        "-std=c++11",
+        "-I..",
+        "-M",
+        "-MG",      // Treat missing headers as generated.
+        "-MQ", "*", // Quoted target (older version can't handle empty name).
+        s.path ().string ().c_str (),
+        nullptr};
+
+      try
+      {
+        process pr (args, false, false, true);
+        bool r (true);
+
+        __gnu_cxx::stdio_filebuf<char> fb (pr.in_ofd, ios_base::in);
+        istream is (&fb);
+
+        for (bool first (true); !is.eof (); )
+        {
+          string l;
+          getline (is, l);
+
+          if (is.fail () && !is.eof ())
+          {
+            cerr << "warning: io error while parsing output" << endl;
+            r = false;
+            break;
+          }
+
+          size_t p (0);
+
+          if (first)
+          {
+            // Empty output usually means the wait() call below will return
+            // false.
+            //
+            if (l.empty ())
+            {
+              r = false;
+              break;
+            }
+
+            first = false;
+            assert (l[0] == '*' && l[1] == ':' && l[2] == ' ');
+            next (l, (p = 3)); // Skip the source file.
+          }
+
+          while (p != l.size ())
+          {
+            path d (next (l, p));
+
+            // If there is no extension (e.g., std C++ headers), then
+            // assume it is a header. Otherwise, let the normall
+            // mechanism to figure the type from the extension.
+            //
+
+            // @@ TODO:
+            //
+            // - memory leak
+
+            hxx& h (*new hxx (d.leaf ().base ().string ()));
+            h.path (d);
+
+            o.prerequisite (h);
+          }
+        }
+
+        //@@ Any diagnostics if wait() returns false. Or do we assume
+        //   the child process issued something?
+        //
+        return pr.wait () && r;
+      }
+      catch (const process_error& e)
+      {
+        cerr << "warning: unable to execute '" << args[0] << "': " <<
+          e.what () << endl;
+
+        if (e.child ())
+          exit (1);
+
+        return false;
+      }
+    }
+
     target_state compile::
     update (target& t)
     {
-- 
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