INT31-C: Exclude stdbool.h

Conversions to bool should be permitted because they are not "lossy".

Author: lcartey

c/cert/src/rules/INT31-C/IntegerConversionCausesDataLoss.ql

@@ -82,7 +82,8 @@ where
     c.getType().getUnspecifiedType() instanceof UnsignedCharType and
     lowerBound(preConversionExpr) >= typeLowerBound(any(SignedCharType s)) and
     upperBound(preConversionExpr) <= typeUpperBound(any(UnsignedCharType s))
-  )
+  ) and
+  not c.getCastedToType() instanceof BoolType
 select c,
   "Conversion from " + c.getPreConversionExpr().getType() + " to " + c.getCastedToType() +
     " may cause data loss."

c/cert/test/rules/INT31-C/test.c

@@ -1,8 +1,8 @@
 #include <limits.h>
+#include <stdbool.h>
 #include <stddef.h>
 #include <stdio.h>
 #include <string.h>
-
 void test_unsigned_to_signed(unsigned int x) {
   (signed int)x; // NON_COMPLIANT - not larger enough to represent all
 }
@@ -105,4 +105,8 @@ void test_funcs(int *a, size_t n) {
   // not supported in our stdlib, or in any of the compilers
   // memset_s(a, rn, 4096, n); // NON_COMPLIANT
   // memset_s(a, rn, 0, n);    // COMPLIANT
+}
+
+void test_bool(signed int s) {
+  (bool)s; // COMPLIANT
 }