Index: tools/fpcmp.c
===================================================================
--- tools/fpcmp.c
+++ tools/fpcmp.c
@@ -53,7 +53,8 @@
   return isDigitChar(C) || isSignedChar(C) || C == '.';
 }
 
-static const char *AdvanceNumber(const char *StartPos, const char *End) {
+static const char *AdvanceNumber(const char *StartPos, const char *End,
+                                 bool NeedsPostDecimalDigit) {
   const char *Pos = StartPos;
   const char *EndOfNumber = NULL;
 
@@ -70,8 +71,9 @@
   // Decimal separator
   if (Pos < End && *Pos == '.') {
     ++Pos;
+    EndOfNumber = Pos;
 
-    // Post-decimal digits (require at least one when period present)
+    // Post-decimal digits
     bool HasPostDecimalDigit = false;
     while (Pos < End && isDigitChar(*Pos)) {
       HasPostDecimalDigit = true;
@@ -79,7 +81,10 @@
       ++Pos;
       EndOfNumber = Pos;
     }
-    if (!HasPostDecimalDigit)
+
+    // Sometimes we require at least one decimal digit when the decimal point is
+    // present.
+    if (NeedsPostDecimalDigit && !HasPostDecimalDigit)
       return EndOfNumber;
   }
 
@@ -250,8 +255,8 @@
 
 int diff_files_with_tolerance(const char *path_a, const char *path_b,
                               double absolute_tolerance,
-                              double relative_tolerance,
-                              bool ignore_whitespace) {
+                              double relative_tolerance, bool ignore_whitespace,
+                              bool post_decimal_digit) {
   /* First, load the file buffers completely into memory. */
   long A_size, B_size;
   char *data_a = load_file(path_a, &A_size);
@@ -303,8 +308,10 @@
       skip_whitespace(&F2NumStart, File2End);
     }
 
-    const char *F1NumEnd = AdvanceNumber(F1NumStart, File1End);
-    const char *F2NumEnd = AdvanceNumber(F2NumStart, File2End);
+    const char *F1NumEnd =
+        AdvanceNumber(F1NumStart, File1End, post_decimal_digit);
+    const char *F2NumEnd =
+        AdvanceNumber(F2NumStart, File2End, post_decimal_digit);
 
     // If one side is a number, but not the other, we found a difference.
     if (!F1NumEnd || !F2NumEnd) {
@@ -369,12 +376,15 @@
 }
 
 void usage() {
-  fprintf(stderr, "usage: %s [-a VALUE] [-r VALUE] [-i] <path-A> <path-B>\n\n",
+  fprintf(stderr,
+          "usage: %s [-a VALUE] [-r VALUE] [-i] [-d] <path-A> <path-B>\n\n",
           g_program);
   fprintf(stderr, "Compare two files using absolute and relative tolerances\n");
   fprintf(stderr, "when comparing differences between two character\n");
   fprintf(stderr, "which could be real numbers\n");
   fprintf(stderr, "The -i switch ignores whitespace differences\n");
+  fprintf(stderr,
+          "The -d switch requires at least one digit after a decimal point\n");
   exit(2);
 }
 
@@ -382,6 +392,7 @@
   double relative_tolerance = 0.0;
   double absolute_tolerance = 0.0;
   bool ignore_whitespace = false;
+  bool post_decimal_digit = false;
   int i;
 
   g_program = argv[0];
@@ -420,6 +431,10 @@
       ignore_whitespace = true;
       break;
 
+    case 'd':
+      post_decimal_digit = true;
+      break;
+
     default:
       fprintf(stderr, "error: invalid argument '%s'\n\n", arg);
       usage();
@@ -432,5 +447,6 @@
   }
 
   return diff_files_with_tolerance(argv[i], argv[i + 1], absolute_tolerance,
-                                   relative_tolerance, ignore_whitespace);
+                                   relative_tolerance, ignore_whitespace,
+                                   post_decimal_digit);
 }