Verify if the test is limited by an ancient stdio with a 256

open file limit.  In this case the test is skipped with a
message showing this limitation when the number of open files
needed for the test is greater than 256.

tests/libtest/lib518.c

@@ -65,6 +65,29 @@ static void close_file_descriptors(void)
   fd = NULL;
 }
 
+static int stdio_limit_256(void)
+{
+  FILE *fpa[300];
+  int i;
+  int ret = 0;
+
+  for (i = 0; i < 300; i++) {
+    fpa[i] = NULL;
+  }
+  for (i = 0; i < 300; i++) {
+    fpa[i] = fopen(DEV_NULL, "r");
+    if (fpa[i] == NULL) {
+      ret = -1;
+      break;
+    }
+  }
+  for (i = 0; i < 300; i++) {
+    if (fpa[i] != NULL)
+      fclose(fpa[i]);
+  }
+  return ret;
+}
+
 static int rlimit(int keep_open)
 {
   int nitems, i;
@@ -235,6 +258,18 @@ static int rlimit(int keep_open)
 
   num_open.rlim_max = NUM_OPEN;
 
+  /* verify that we don't have an ancient stdio */
+
+  if (((size_t)(num_open.rlim_max) > (size_t)256) && stdio_limit_256()) {
+    sprintf(strbuff1, fmt, num_open.rlim_max);
+    sprintf(strbuff, "fds needed %s > stdio limit 256",
+            strbuff1);
+    store_errmsg(strbuff, 0);
+    fprintf(stderr, "%s\n", msgbuff);
+    free(memchunk);
+    return -12;
+  }
+
   /* verify that we won't overflow size_t in malloc() */
 
   if ((size_t)(num_open.rlim_max) > ((size_t)-1) / sizeof(*fd)) {

tests/libtest/lib537.c

@@ -67,6 +67,29 @@ static void close_file_descriptors(void)
   fd = NULL;
 }
 
+static int stdio_limit_256(void)
+{
+  FILE *fpa[300];
+  int i;
+  int ret = 0;
+
+  for (i = 0; i < 300; i++) {
+    fpa[i] = NULL;
+  }
+  for (i = 0; i < 300; i++) {
+    fpa[i] = fopen(DEV_NULL, "r");
+    if (fpa[i] == NULL) {
+      ret = -1;
+      break;
+    }
+  }
+  for (i = 0; i < 300; i++) {
+    if (fpa[i] != NULL)
+      fclose(fpa[i]);
+  }
+  return ret;
+}
+
 static int rlimit(int keep_open)
 {
   int *tmpfd;
@@ -225,6 +248,18 @@ static int rlimit(int keep_open)
     num_open.rlim_max = nitems;
   }
 
+  /* verify that we don't have an ancient stdio */
+
+  if (((size_t)(num_open.rlim_max) > (size_t)256) && stdio_limit_256()) {
+    sprintf(strbuff1, fmt, num_open.rlim_max);
+    sprintf(strbuff, "fds needed %s > stdio limit 256",
+            strbuff1);
+    store_errmsg(strbuff, 0);
+    fprintf(stderr, "%s\n", msgbuff);
+    free(memchunk);
+    return -10;
+  }
+
   /* verify that we won't overflow size_t in malloc() */
 
   if ((size_t)(num_open.rlim_max) > ((size_t)-1) / sizeof(*fd)) {