Page History

Wiki MarkupAn empty infinite loop that does not do anything within the loop body is a suboptimal solution, and no code should use it. The solution is suboptimal because it consumes CPU cycles but does nothing. An optimizing compiler can remove such a loop, and it can lead to unexpected results. According to C1X Committee Draft \[[ISO/IEC 9899:201x|AA. Bibliography#ISO/IEC 9899-201x]\], Section 6.8.5.6

An iteration statement that performs no input/output operations does not access volatile objects, and performs no synchronization or atomic operations in its body, controlling expression, or (in the case of a for statement) its expression-3, may be assumed by the implementation to terminate.¹⁵⁵

155) This is intended to allow compiler transformations, such as removal of empty loops, even when termination cannot be proven.

Noncompliant Code Example

...

int main(void) {
  /* set up buffers, signal handlers for interrupts, etc. */
  /* ... */
  for ( ; ; ) {
    sleep(DURATION);	/* let interrupt handler do all the work */
  }
  /* not reached */
}

void rcv_intr(int interrupt) { /* signal handler entered upon data_available interrupt */
  /* ... */
  get_packet();  /* read the packet */
  if (packet.hdr.service == ICMP_ECHO) {
    send_packet();  /* send the packet */
  }
  /* ... */
}

Exceptions

MSC40MSC01-EX1EX0: In rare cases, use of an empty infinite loop may be unavoidable. For instance, an empty loop may be necessary on a platform that does not support sleep(3) or an equivalent function. Another example occurs in operating system kernels. A task started before normal scheduler functionality is available may not have access to sleep(3) or an equivalent function. In such a case, it is necessary to adopt alternative solutions that prevent an optimizing compiler from removing the empty infinite loop.

...

Bibliography

\[[API 2006|https://www.securecoding.cert.org/confluence/display/java/AA.+Java+References#AA.JavaReferences-API06]\]

...

SER03-J. Prevent serialization of unencrypted, sensitive data      16. Serialization (SER)      SER05-J. Do not allow serialization and deserialization to bypass the Security Manager