INT32-C: Report issues in guards

Signed integer overflow and underflow is undefined behavior, and so,
unlike unsigned wraparound, it's not valid to do so even in a guard
condition.

Author: lcartey

c/cert/src/rules/INT32-C/SignedIntegerOverflow.ql

@@ -22,8 +22,6 @@ from InterestingBinaryOverflowingExpr bop
 where
   not isExcluded(bop, IntegerOverflowPackage::signedIntegerOverflowQuery()) and
   bop.getType().getUnderlyingType().(IntegralType).isSigned() and
-  // Not within a guard condition
-  not exists(GuardCondition gc | gc.getAChild*() = bop) and
   // Not checked before the operation
   not bop.hasValidPreCheck() and
   // Not guarded by a check, where the check is not an invalid overflow check

c/cert/test/rules/INT32-C/SignedIntegerOverflow.expected

@@ -1,4 +1,5 @@
 | test.c:6:3:6:9 | ... + ... | Binary expression ...+... of type int may overflow or underflow. |
+| test.c:20:7:20:13 | ... + ... | Binary expression ...+... of type int may overflow or underflow. |
 | test.c:23:5:23:11 | ... + ... | Binary expression ...+... of type int may overflow or underflow. |
 | test.c:28:19:28:25 | ... + ... | Binary expression ...+... of type int may overflow or underflow. |
 | test.c:36:3:36:9 | ... - ... | Binary expression ...-... of type int may overflow or underflow. |