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Noncompliant Code Example

In the following this noncompliant code example, the programmer is targeting a custom piece of hardware that controls an LED by writing values into a register bank. The register bank is memory mapped into the process such that writing to a specific memory location will actually place a value into a hardware register to be read by the LED controller. The programmer intends to turn the LED on by placing value 1 into the first register, and then turn the LED off later by placing the value 0 into the first register.

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#include <stddef.h>
#include <stdint.h>

extern void get_register_bank(volatile int32_t **bank,
                              size_t *num_registers);
extern void external_wait(void);

void func(void) {
  volatile int32_t bank[3];
  size_t num_regs = 3;

  get_register_bank((volatile int32_t **)&bank, &num_regs);
  if (num_regs < 3) {
    /* Handle error */
   }

  bank[0] = 1;
  external_wait();
  bank[0] = 0;
}

Risk Assessment

Blah blah blahFailure to declare variables containing data that cannot be cached as volatile can result in unexpected runtime behavior resulting from compiler optimizations.

Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

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