Support empty depfiles.

Some tools generate completely empty depfiles when
there are no implicit inputs. This patch modifies the
depfile parser to support them.

Fixes #2357

1 files changed, 3 insertions, 1 deletions

diff --git a/src/depfile_parser.cc b/src/depfile_parser.cc
index 98fba2e..7ce7290 100644
--- a/src/depfile_parser.cc
+++ b/src/depfile_parser.cc
@@ -54,6 +54,7 @@ bool DepfileParser::Parse(string* content, string* err) {
   bool have_target = false;
   bool parsing_targets = true;
   bool poisoned_input = false;
+  bool is_empty = true;
   while (in < end) {
     bool have_newline = false;
     // out: current output point (typically same as in, but can fall behind
@@ -335,6 +336,7 @@ yy32:
     }
 
     if (len > 0) {
+      is_empty = false;
       StringPiece piece = StringPiece(filename, len);
       // If we've seen this as an input before, skip it.
       std::vector<StringPiece>::iterator pos = std::find(ins_.begin(), ins_.end(), piece);
@@ -363,7 +365,7 @@ yy32:
       poisoned_input = false;
     }
   }
-  if (!have_target) {
+  if (!have_target && !is_empty) {
     *err = "expected ':' in depfile";
     return false;
   }