Always rebuild on errors

https://groups.google.com/forum/#!msg/ninja-build/YQuGNrECI-4/ti-lAs9SPv8J
discusses a case where an rule updates its output file and then
fails.  The next run of ninja considers the ouptut file clean
and doesn't rebuild it.  Always stat output files after they are
built, and write the mtime into .ninja_log.  Consider output files
dirty if the recorded mtime is older than the most recent input
file.

1 files changed, 19 insertions, 7 deletions

diff --git a/src/graph.cc b/src/graph.cc
index 76d996b..27013d5 100644
--- a/src/graph.cc
+++ b/src/graph.cc
@@ -168,7 +168,7 @@ bool DependencyScan::RecomputeOutputDirty(Edge* edge,
     bool used_restat = false;
     if (edge->GetBindingBool("restat") && build_log() &&
         (entry = build_log()->LookupByOutput(output->path()))) {
-      output_mtime = entry->restat_mtime;
+      output_mtime = entry->mtime;
       used_restat = true;
     }
 
@@ -182,17 +182,29 @@ bool DependencyScan::RecomputeOutputDirty(Edge* edge,
     }
   }
 
-  // May also be dirty due to the command changing since the last build.
-  // But if this is a generator rule, the command changing does not make us
-  // dirty.
-  if (!edge->GetBindingBool("generator") && build_log()) {
+  if (build_log()) {
+    bool generator = edge->GetBindingBool("generator");
     if (entry || (entry = build_log()->LookupByOutput(output->path()))) {
-      if (BuildLog::LogEntry::HashCommand(command) != entry->command_hash) {
+      if (!generator &&
+          BuildLog::LogEntry::HashCommand(command) != entry->command_hash) {
+        // May also be dirty due to the command changing since the last build.
+        // But if this is a generator rule, the command changing does not make us
+        // dirty.
         EXPLAIN("command line changed for %s", output->path().c_str());
         return true;
       }
+      if (entry->mtime < most_recent_input->mtime()) {
+        // May also be dirty due to the mtime in the log being older than the
+        // mtime of the most recent input.  This can occur even when the mtime
+        // on disk is newer if a previous run wrote to the output file but
+        // exited with an error or was interrupted.
+        EXPLAIN("recorded mtime of %s older than most recent input %s (%d vs %d)",
+                output->path().c_str(), most_recent_input->path().c_str(),
+                entry->mtime, most_recent_input->mtime());
+        return true;
+      }
     }
-    if (!entry) {
+    if (!entry && !generator) {
       EXPLAIN("command line not found in log for %s", output->path().c_str());
       return true;
     }