Avoid running into nonexistent system calls repeatedly.

[gnulib.git] / lib / pipe2.c

diff --git a/lib/pipe2.c b/lib/pipe2.c
index c18860d..d3b612d 100644 (file)
--- a/lib/pipe2.c
+++ b/lib/pipe2.c
@@ -45,9 +45,18 @@ pipe2 (int fd[2], int flags)
   /* Try the system call first, if it exists.  (We may be running with a glibc
      that has the function but with an older kernel that lacks it.)  */
   {
-    int result = pipe2 (fd, flags);
-    if (!(result < 0 && errno == ENOSYS))
-      return result;
+    /* Cache the information whether the system call really exists.  */
+    static int have_pipe2_really; /* 0 = unknown, 1 = yes, -1 = no */
+    if (have_pipe2_really >= 0)
+      {
+       int result = pipe2 (fd, flags);
+       if (!(result < 0 && errno == ENOSYS))
+         {
+           have_pipe2_really = 1;
+           return result;
+         }
+       have_pipe2_really = -1;
+      }
   }
 #endif