[MSAN] print out the only possible invalid parameter (EINVAL is returned)

[kda]

Summary

One more round attempting to figure what is wrong.

Depends on: https://reviews.llvm.org/D127346

[vitalybuka]

maybe #define _GNU_SOURCE as in documentation?

[kda]

defined _GNU_SOURCE (as recommended), print out sizeof(set_x)

compiler-rt/test/sanitizer_common/TestCases/Linux/pthread_getaffinity_np.cpp

 // RUN: %clangxx -O0 %s -o %t && %run %t
 
 // Android does not implement pthread_getaffinity_np.
 // (Note: libresolv is integrated with libc, but apparently only
 // sched_getaffinity).
 // UNSUPPORTED: android
 
+#ifndef _GNU_SOURCE
+#  define _GNU_SOURCE
+#endif
+
 #include <assert.h>
 #include <pthread.h>
 #include <stdio.h>
 #include <sys/sysinfo.h>
 
 #include <sanitizer/msan_interface.h>
 
 int main() {
   cpu_set_t set_x;
-  int res = pthread_getaffinity_np(pthread_self(), sizeof(set_x), &set_x);
-  if (res != 0)
+  pthread_t tid = pthread_self();
+  int res = pthread_getaffinity_np(tid, sizeof(set_x), &set_x);
+  if (res != 0) {
+    fprintf(stderr, "tid: %lu\n", tid);
+    fprintf(stderr, "sizeof(set_x): %d\n", sizeof(set_x));
     fprintf(stderr, "res: %d\n", res);
+  }
   assert(res == 0);
   assert(CPU_COUNT_S(sizeof(set_x), &set_x) == get_nprocs());
 
   return 0;
 }