c: ex2: add solution

c/ex2.c

@@ -0,0 +1,30 @@
+#include <stdio.h>
+#include <string.h>
+
+char* f(int m) {
+    char buf[6];
+    int x;
+
+    if (m == 1 && x-- /* variable is read before initialization */) {
+        strcpy(buf, "AAAAAA"); // null-byte copy overflows buffer at index 7
+        return buf;            // Return stack allocated array
+    } else if (m == 2) {
+        char* msg = (char*)malloc(100); // malloc is declared in <stdlib.h>
+        // While technically not UB, as it will be implicitly declared by the
+        // compiler, this is error-prone and the implicit declaration most
+        // likely does not match the actual function
+        strcpy(msg, "BBBBBB");
+        return msg;
+    }
+    // Missing return value
+}
+
+int main(int argc, char** argv) {
+    char* m;
+    m = f(argc);
+    putchar(m[0]); // if m != 2, either reads garbage stack memory or
+                   // non-sensical pointer due to missing return value
+    return 0;
+    // Potential memory leak, if m == 2
+    // While not UB, it is frowned upon
+}