extern int printf (const char *__restrict __format, ...);

extern int sprintf (char *__restrict __s,
      const char *__restrict __format, ...) __attribute__ ((__nothrow__));

#ifdef CONFIG_RCU_CPU_STALL_INFO

#ifdef CONFIG_RCU_FAST_NO_HZ
void print_cpu_stall_fast_no_hz(char *cp, int cpu)
{
  sprintf(cp, "foobar");
}
#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
void print_cpu_stall_fast_no_hz(char *cp, int cpu)
{ // (3)
}
#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */

void print_cpu_stall_info(int cpu)
{
  char fast_no_hz[72];

  print_cpu_stall_fast_no_hz(fast_no_hz, cpu); // (2)
  printf("\t%d: %s\n", cpu, fast_no_hz); // ERROR (4)
}
#else /* #ifdef CONFIG_RCU_CPU_STALL_INFO */
void print_cpu_stall_info(int cpu)
{
  printf(" %d", cpu);
}
#endif /* #else #ifdef CONFIG_RCU_CPU_STALL_INFO */

int main(void)
{
#ifdef CONFIG_RCU_CPU_STALL_INFO
  print_cpu_stall_info(0); // (1)
#endif
  return 0;
}

diff --git a/simple/1c17e4d.c b/simple/1c17e4d.c
--- a/simple/1c17e4d.c
+++ b/simple/1c17e4d.c
@@ -14,6 +14,7 @@
 #else /* #ifdef CONFIG_RCU_FAST_NO_HZ */
 void print_cpu_stall_fast_no_hz(char *cp, int cpu)
 { // (3)
+  *cp = '\0';
 }
 #endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */
 

#include <stdio.h>

int main(int argc, char** argv) {
#ifdef CONFIG_RCU_CPU_STALL_INFO
//  print_cpu_stall_info(0);
  char fast_no_hz[72];
  int cpu = 0;
  
  #ifdef CONFIG_RCU_FAST_NO_HZ
  sprintf(fast_no_hz, "foobar");
  #else
  
  #endif
  printf("\t%d: %s\n", cpu, fast_no_hz); // ERROR
#else
  printf(" %d", cpu);
#endif
  return 0;
}

. call kernel/rcutree_plugin.h:2249: print_cpu_stall_info()
. 2264: print_cpu_stall_fast_no_hz(fast_no_hz, cpu);
.. call kernel/rcutree_plugin.h:2225:print_cpu_stall_fast_no_hz()
.. 2227: }
// fast_no_hz is left uninitialized
. ERROR 2265: printk(KERN_ERR "\t%d: (%lu %s) idle=%03x/%llx/%d %s\n",