Fixed fcntl

src/rtcheck.cpp

@@ -575,10 +575,21 @@ INTERCEPTOR(int, fcntl, int filedes, int cmd, ...)
 
     va_list args;
     va_start(args, cmd);
-    void *arg = va_arg(args, void*);
+
+    // From RTsan:
+    // Following precedent here. The linux source (fcntl.c, do_fcntl) accepts the
+    // final argument in a variable that will hold the largest of the possible
+    // argument types (pointers and ints are typical in fcntl) It is then assumed
+    // that the implementation of fcntl will cast it properly depending on cmd.
+    //
+    // This is also similar to what is done in
+    // sanitizer_common/sanitizer_common_syscalls.inc
+    const unsigned long arg = va_arg(args, unsigned long);
+    int result = REAL(fcntl)(filedes, cmd, arg);
+
     va_end(args);
 
-    return fcntl(filedes, cmd, arg);
+    return result;
 }
 
 //==============================================================================