From eee4910fb7189773074e4c89d4ba249704ba5d11 Mon Sep 17 00:00:00 2001
From: Nico Weber <nicolasweber@gmx.de>
Date: Tue, 9 Apr 2013 09:58:54 -0700
Subject: On invalid depslog header, restart build instead of showing an error.

Also add tests for invalid headers.
---
 src/deps_log.cc      | 14 +++++---------
 src/deps_log_test.cc | 26 ++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/src/deps_log.cc b/src/deps_log.cc
index 8946e32..79daba5 100644
--- a/src/deps_log.cc
+++ b/src/deps_log.cc
@@ -136,16 +136,12 @@ bool DepsLog::Load(const string& path, State* state, string* err) {
     return false;
   }
 
-  if (!fgets(buf, sizeof(buf), f)) {
-    *err = strerror(errno);
-    return false;
-  }
+  bool valid_header = true;
   int version = 0;
-  if (fread(&version, 4, 1, f) < 1) {
-    *err = strerror(errno);
-    return false;
-  }
-  if (version != kCurrentVersion) {
+  if (!fgets(buf, sizeof(buf), f) || fread(&version, 4, 1, f) < 1)
+    valid_header = false;
+  if (!valid_header || strcmp(buf, kFileSignature) != 0 ||
+      version != kCurrentVersion) {
     *err = "bad deps log signature or version; starting over";
     fclose(f);
     unlink(path.c_str());
diff --git a/src/deps_log_test.cc b/src/deps_log_test.cc
index 2d91c0e..06fffeb 100644
--- a/src/deps_log_test.cc
+++ b/src/deps_log_test.cc
@@ -192,4 +192,30 @@ TEST_F(DepsLogTest, Recompact) {
   }
 }
 
+// Verify that invalid file headers cause a new build.
+TEST_F(DepsLogTest, InvalidHeader) {
+  const char *kInvalidHeaders[] = {
+    "",                              // Emtpy file.
+    "# ninjad",                      // Truncated first line.
+    "# ninjadeps\n",                 // No version int.
+    "# ninjadeps\n\001\002",         // Truncated version int.
+    "# ninjadeps\n\001\002\003\004"  // Invalid version int.
+  };
+  for (size_t i = 0; i < sizeof(kInvalidHeaders) / sizeof(kInvalidHeaders[0]);
+       ++i) {
+    FILE* deps_log = fopen(kTestFilename, "wb");
+    ASSERT_TRUE(deps_log != NULL);
+    ASSERT_EQ(
+        strlen(kInvalidHeaders[i]),
+        fwrite(kInvalidHeaders[i], 1, strlen(kInvalidHeaders[i]), deps_log));
+    ASSERT_EQ(0 ,fclose(deps_log));
+
+    string err;
+    DepsLog log;
+    State state;
+    ASSERT_TRUE(log.Load(kTestFilename, &state, &err));
+    EXPECT_EQ("bad deps log signature or version; starting over", err);
+  }
+}
+
 }  // anonymous namespace
-- 
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