modify use after free runtime testing to avoid compile-time detection

Author: andrew-taylor

tests/expected_output/use_after_free/000001-clang-14.0-x86_64-pc-linux-gnu.txt

@@ -0,0 +1,20 @@
+=================================================================
+
+tests/run_time_errors/use_after_free.c:9 runtime error - malloc use after free
+
+dcc explanation: access to memory that has already been freed.
+
+Execution stopped in main() in tests/run_time_errors/use_after_free.c at line 9:
+
+int main(int argc, char *argv[]) {
+    int *p = (int *)malloc(sizeof(int *));
+    *p = 1;
+    if (argc > 0) {
+        free(p);
+    }
+--> return *p;
+}
+
+Values when execution stopped:
+
+argc = 1

tests/expected_output/use_after_return--use-after-return/000001-clang-14.0-x86_64-pc-linux-gnu.txt

@@ -0,0 +1,13 @@
+=================================================================
+
+tests/run_time_errors/use_after_return.c:26 runtime error - stack use after return
+
+dcc explanation: You have used a pointer to a local variable that no longer exists.
+  When a function returns its local variables are destroyed.
+
+For more information see: https://comp1511unsw.github.io/dcc/stack_use_after_return.html
+Execution stopped in main() in tests/run_time_errors/use_after_return.c at line 26:
+
+int main(void) {
+-->	printf("%d\n", *f(50));
+}

tests/run_time_errors/use_after_free.c

@@ -1,8 +1,10 @@
 #include <stdlib.h>
 
-int main(void) {
-    int *p = (int *)malloc(sizeof (int *));
+int main(int argc, char *argv[]) {
+    int *p = (int *)malloc(sizeof(int *));
     *p = 1;
-    free(p);
+    if (argc > 0) {
+        free(p);
+    }
     return *p;
 }

tests/run_time_errors/use_after_return.c

@@ -15,6 +15,9 @@ int * f(int num) {
     }
     factors[0] = count;
     int *factorPointer = factors;
+    if (num == 0) {
+    	factorPointer = NULL;
+    }
     return factorPointer;
 
 }