Incorporate target to link rule's depdb

Since there is no guarantee that the target is part of the linker's checksum.

3 files changed, 16 insertions, 2 deletions

diff --git a/build2/cxx/compile.cxx b/build2/cxx/compile.cxx
index 300fad7..5205fdf 100644
--- a/build2/cxx/compile.cxx
+++ b/build2/cxx/compile.cxx
@@ -210,7 +210,9 @@ namespace build2
         if (dd.expect ("cxx.compile 1") != nullptr)
           l4 ([&]{trace << "rule mismatch forcing update of " << t;});
 
-        // Then the compiler checksum.
+        // Then the compiler checksum. Note that here we assume it
+        // incorporates the (default) target so that if the compiler changes
+        // but only in what it targets, then the checksum will still change.
         //
         if (dd.expect (cast<string> (rs["cxx.checksum"])) != nullptr)
           l4 ([&]{trace << "compiler mismatch forcing update of " << t;});
diff --git a/build2/cxx/guess b/build2/cxx/guess
index 0588523..63858ad 100644
--- a/build2/cxx/guess
+++ b/build2/cxx/guess
@@ -86,6 +86,11 @@ namespace build2
     // common cases, such as an upgrade to a new version or a configuration
     // change.
     //
+    // Note that we assume the checksum incorporates the (default) target so
+    // that if the compiler changes but only in what it targets, then the
+    // checksum will still change. This is currently the case for all the
+    // compilers that we support.
+    //
     // The target is the compiler's traget architecture triplet. Note that
     // unlike all the preceding fields, this one takes into account the
     // compile options (e.g., -m32).
diff --git a/build2/cxx/link.cxx b/build2/cxx/link.cxx
index 3ce99c9..e714bc1 100644
--- a/build2/cxx/link.cxx
+++ b/build2/cxx/link.cxx
@@ -1091,6 +1091,7 @@ namespace build2
       scope& rs (t.root_scope ());
 
       const string& cid (cast<string> (rs["cxx.id"]));
+      const string& tgt (cast<string> (rs["cxx.target"]));
       const string& tsys (cast<string> (rs["cxx.target.system"]));
       const string& tclass (cast<string> (rs["cxx.target.class"]));
 
@@ -1239,6 +1240,12 @@ namespace build2
           l4 ([&]{trace << "linker mismatch forcing update of " << t;});
       }
 
+      // Next check the target. While it might be incorporated into the linker
+      // checksum, it also might not (e.g., MS link.exe).
+      //
+      if (dd.expect (tgt) != nullptr)
+        l4 ([&]{trace << "target mismatch forcing update of " << t;});
+
       // Start building the command line. While we don't yet know whether we
       // will really need it, we need to hash it to find out. So the options
       // are to either replicate the exact process twice, first for hashing
@@ -1292,7 +1299,7 @@ namespace build2
           auto l (t["bin.rpath"]);
 
           if (l && !l->empty ())
-            fail << cast<string> (rs["cxx.target"]) << " does not have rpath";
+            fail << tgt << " does not support rpath";
         }
         else
         {