Make version generation robust to other user-defined tags.

src/version.cc

Index: src/version.cc
diff --git a/src/version.cc b/src/version.cc
index d7c937c7aac7e18835fbbcde311ca6889e4b2b9d..300f1731fd8ef3cd4e147762cc465d4ee5498464 100644
--- a/src/version.cc
+++ b/src/version.cc
@@ -17,15 +17,22 @@
 // (Boolean macro values are not supported by all preprocessors.)
 #define IS_CANDIDATE_VERSION 1
 
+// Used to mark a version built from a bad tag.
+#define IS_INVALID_VERSION 0
+
 // Define SONAME to have the build system put a specific SONAME into the
 // shared library instead the generic SONAME generated from the V8 version
 // number. This define is mainly used by the build system script.
 #define SONAME            ""
 
+#if IS_INVALID_VERSION
+#define SUFFIX_STRING " (invalid)"
+#else
 #if IS_CANDIDATE_VERSION
-#define CANDIDATE_STRING " (candidate)"
+#define SUFFIX_STRING " (candidate)"
 #else
-#define CANDIDATE_STRING ""
+#define SUFFIX_STRING ""
+#endif
 #endif
 
 #define SX(x) #x
@@ -33,12 +40,11 @@
 
 #if PATCH_LEVEL > 0
 #define VERSION_STRING                                                         \
-    S(MAJOR_VERSION) "." S(MINOR_VERSION) "." S(BUILD_NUMBER) "."              \
-        S(PATCH_LEVEL) CANDIDATE_STRING
+  S(MAJOR_VERSION) "." S(MINOR_VERSION) "." S(BUILD_NUMBER) "." S(PATCH_LEVEL) \
+      SUFFIX_STRING
 #else
-#define VERSION_STRING                                                         \
-    S(MAJOR_VERSION) "." S(MINOR_VERSION) "." S(BUILD_NUMBER)                  \
-        CANDIDATE_STRING
+#define VERSION_STRING \
+  S(MAJOR_VERSION) "." S(MINOR_VERSION) "." S(BUILD_NUMBER) SUFFIX_STRING
 #endif
 
 namespace v8 {