0 Replies Latest reply on Sep 5, 2016 12:39 AM by 3034537

    spurious warning with builtin atomics ?

    3034537

      Dear support,

       

      this topic was initially discussed at https://github.com/open-mpi/ompi/pull/2032#issuecomment-244311963 (for reference only)

       

       

      oracle compilers (i tested the latest 12.5 on Linux) do issue some warning when builtin atomics are used, and they look like spurious warnings to me

       

      let's try this sample program

       

      #include <stdbool.h>
      static inline int atomic( volatile int *addr, int oldval, int newval) {
        return __atomic_compare_exchange_n (addr, &oldval, newval, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
      }
      

      gcc

      is perfectly happy with that, even with the -Wall

      option

      but cc is not

      $ /opt/oracle/developerstudio12.5/bin/cc -c atomic.c "atomic.c", line 5: warning: argument #2 is incompatible with prototype:
      prototype: pointer to void : "atomic.c",
      line 0 argument : pointer to volatile int

      if i modify this program like this

       

      #include <stdbool.h>
      static inline int atomic( volatile int *addr, int oldval, int newval) {
        return __atomic_compare_exchange_n (addr, (void *)&oldval, newval, false, __ATOMIC_ACQUIRE, __ATOMIC_RELAXED);
      }
      

      gcc -Wall is still very happy, but thing got worst from cc point of view

      $ /opt/oracle/developerstudio12.5/bin/cc -c atomic.c "atomic.c", line 6: argument #2 of "__atomic_compare_exchange_n" should be non-void pointer type "atomic.c",
      line 5: warning: argument #2 is incompatible with prototype:
      prototype: pointer to void : "atomic.c",
      line 0 argument : pointer to volatile int

      if i read correctly
      1. the second argument should not be a void *
      2. the second argument is a volatile int * but a void * is expected !!!

       

       

      to me, that looks like a spurious warning, could you please comment on that ?

       

      Thanks and regards,

       

      Gilles