Restore depfile toleration of multiple output paths on distinct lines

Prior to introduction of depfile parser handling of multiple rules,
ninja silently accepted a depfile of the form:

    out: in1 in2 in3
    other: otherIn1 otherIn2 otherIn3

and incorrectly treated `other` and `otherIn*` as additional inputs to
`out`.  Now we prefer to reject this just as we already do for a depfile
specifying multiple outputs on one line.  However, this can break
existing cases where such a depfile was silently tolerated.

Add a `-w depfilemulti={err,warn}` option to control this behavior,
and make it just a warning by default.

1 files changed, 28 insertions, 2 deletions

diff --git a/src/depfile_parser.cc b/src/depfile_parser.cc
index 7724eed..405289f 100644
--- a/src/depfile_parser.cc
+++ b/src/depfile_parser.cc
@@ -14,6 +14,12 @@
 // limitations under the License.
 
 #include "depfile_parser.h"
+#include "util.h"
+
+DepfileParser::DepfileParser(DepfileParserOptions options)
+  : options_(options)
+{
+}
 
 // A note on backslashes in Makefiles, from reading the docs:
 // Backslash-newline is the line continuation character.
@@ -37,6 +43,8 @@ bool DepfileParser::Parse(string* content, string* err) {
   char* end = in + content->size();
   bool have_target = false;
   bool have_secondary_target_on_this_rule = false;
+  bool have_newline_since_primary_target = false;
+  bool warned_distinct_target_lines = false;
   bool parsing_targets = true;
   while (in < end) {
     bool have_newline = false;
@@ -219,8 +227,23 @@ yy22:
     if (len > 0) {
       if (is_dependency) {
         if (have_secondary_target_on_this_rule) {
-          *err = "depfile has multiple output paths";
-          return false;
+          if (!have_newline_since_primary_target) {
+            *err = "depfile has multiple output paths";
+            return false;
+          } else if (options_.depfile_distinct_target_lines_action_ ==
+                     kDepfileDistinctTargetLinesActionError) {
+            *err =
+                "depfile has multiple output paths (on separate lines)"
+                " [-w depfilemulti=err]";
+            return false;
+          } else {
+            if (!warned_distinct_target_lines) {
+              warned_distinct_target_lines = true;
+              Warning("depfile has multiple output paths (on separate lines); "
+                      "continuing anyway [-w depfilemulti=warn]");
+            }
+            continue;
+          }
         }
         ins_.push_back(StringPiece(filename, len));
       } else if (!out_.str_) {
@@ -234,6 +257,9 @@ yy22:
       // A newline ends a rule so the next filename will be a new target.
       parsing_targets = true;
       have_secondary_target_on_this_rule = false;
+      if (have_target) {
+        have_newline_since_primary_target = true;
+      }
     }
   }
   if (!have_target) {