Leap Year Examples

Author: bdrodes

cpp/ql/src/Microsoft/Leap Year/examples/LeapYearConditionalLogicBad.c

@@ -0,0 +1,21 @@
+// Checking for leap year
+bool isLeapYear = year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+if (isLeapYear)
+{
+    // untested path
+}
+else
+{
+    // tested path
+}
+
+
+// Checking specifically for the leap day
+if (month == 2 && day == 29)  // (or 1 with a tm_mon value)
+{
+    // untested path
+}
+else
+{
+    // tested path
+}

cpp/ql/src/Microsoft/Leap Year/examples/UncheckedLeapYearAfterYearModificationBad.c

@@ -0,0 +1,9 @@
+SYSTEMTIME st;
+FILETIME ft;
+GetSystemTime(&st);
+
+// Flawed logic may result in invalid date
+st.wYear++;
+
+// The following code may fail
+SystemTimeToFileTime(&st, &ft);

cpp/ql/src/Microsoft/Leap Year/examples/UncheckedLeapYearAfterYearModificationGood.c

@@ -0,0 +1,15 @@
+SYSTEMTIME st;
+FILETIME ft;
+GetSystemTime(&st);
+
+// Flawed logic may result in invalid date
+st.wYear++;
+
+// Check for leap year, and adjust the date accordingly
+bool isLeapYear = st.wYear % 4 == 0 && (st.wYear % 100 != 0 || st.wYear % 400 == 0);
+st.wDay = st.wMonth == 2 && st.wDay == 29 && !isLeapYear ? 28 : st.wDay;
+
+if (!SystemTimeToFileTime(&st, &ft))
+{
+	// handle error
+}

cpp/ql/src/Microsoft/Leap Year/examples/UnsafeArrayForDaysOfYearBad.c

@@ -0,0 +1,2 @@
+int items[365];
+items[dayOfYear - 1] = x; // buffer overflow on December 31st of any leap year 

cpp/ql/src/Microsoft/Leap Year/examples/UnsafeArrayForDaysOfYearGood.c

@@ -0,0 +1,4 @@
+bool isLeapYear = year % 4 == 0 && (year % 100 != 0 || year % 400 == 0);
+int *items = new int[isLeapYear ? 366 : 365];
+// ...
+delete[] items;