C++: Add a test of unsigned count-down loops.

Author: geoffw0

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/inconsistentLoopDirection/inconsistentLoopDirection.cpp

@@ -177,4 +177,21 @@ void FalseNegativeTestCases()
     for (int i = 100; i > 0; i += 2) {}
     // For comparison
     for (int i = 100; i > 0; i ++ ) {}  // BUG
+}
+
+void IntendedOverflow()
+{
+    const unsigned char m = 10;
+    unsigned char i;
+    signed char s;
+
+    for (i = 63; i < 64; i--) {} // GOOD (legitimate way to count down with an unsigned) [FALSE POSITIVE]
+    for (i = 63; i < 128; i--) {} // DUBIOUS (could still be a typo?)
+    for (i = 63; i < 255; i--) {} // GOOD [FALSE POSITIVE]
+
+    for (i = m - 1; i < m; i--) {} // GOOD [FALSE POSITIVE]
+    for (i = m - 1; i < m; i--) {} // DUBIOUS
+    for (i = m - 1; i < m; i--) {} // GOOD [FALSE POSITIVE]
+
+    for (s = 63; s < 64; s--) {} // BAD (signed numbers don't wrap at 0 / at all)
 }

cpp/ql/test/query-tests/Likely Bugs/Likely Typos/inconsistentLoopDirection/inconsistentLoopDirection.expected

@@ -20,3 +20,10 @@
 | inconsistentLoopDirection.cpp:140:5:142:5 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts upward from a value (200), but the terminal condition is lower (0). |
 | inconsistentLoopDirection.cpp:175:5:175:36 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (0), but the terminal condition is higher (10). |
 | inconsistentLoopDirection.cpp:179:5:179:38 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts upward from a value (100), but the terminal condition is lower (0). |
+| inconsistentLoopDirection.cpp:188:5:188:32 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (63), but the terminal condition is higher (64). |
+| inconsistentLoopDirection.cpp:189:5:189:33 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (63), but the terminal condition is higher (128). |
+| inconsistentLoopDirection.cpp:190:5:190:33 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (63), but the terminal condition is higher (255). |
+| inconsistentLoopDirection.cpp:192:5:192:34 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (... - ...), but the terminal condition is higher (m). |
+| inconsistentLoopDirection.cpp:193:5:193:34 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (... - ...), but the terminal condition is higher (m). |
+| inconsistentLoopDirection.cpp:194:5:194:34 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "i" counts downward from a value (... - ...), but the terminal condition is higher (m). |
+| inconsistentLoopDirection.cpp:196:5:196:32 | for(...;...;...) ... | Ill-defined for-loop: a loop using variable "s" counts downward from a value (63), but the terminal condition is higher (64). |