From: Eric Wong <normalperson@yhbt.net>
Date: Wed, 7 Mar 2012 10:27:46 +0000 (+0000)
Subject: avoid uname() for pipe size modification checks
X-Git-Tag: v4.2.0~4
X-Git-Url: https://repo.or.cz/w/ruby_io_splice.git/commitdiff_plain/f2a1b8e5f3b9b9ba0c8593bab6d58def3b75e6a4

avoid uname() for pipe size modification checks

The uname comparison is fragile and we can better
detect this during the Init_* function by just using
a pipe.
---

diff --git a/ext/io_splice/io_splice_ext.c b/ext/io_splice/io_splice_ext.c
index cbbdbfc..4c713d1 100644
--- a/ext/io_splice/io_splice_ext.c
+++ b/ext/io_splice/io_splice_ext.c
@@ -10,7 +10,7 @@
 #include <sys/uio.h>
 #include <limits.h>
 #include <alloca.h>
-#include <sys/utsname.h>
+#include <unistd.h>
 
 static VALUE sym_EAGAIN;
 #define WAITALL 0x4000000
@@ -621,10 +621,28 @@ static VALUE set_pipe_size(VALUE self, VALUE size)
 	return size;
 }
 
+static int can_mod_pipe_size(void)
+{
+	int fds[2];
+	int rc = pipe(fds);
+
+	if (rc == 0) {
+		rc = fcntl(fds[0], F_GETPIPE_SZ);
+		rc = rc < 0 ? 0 : 1;
+
+		(void)close(fds[0]);
+		(void)close(fds[1]);
+	} else {
+		/* weird error, but don't raise during init */
+		rc = 0;
+	}
+	errno = 0;
+	return rc;
+}
+
 void Init_io_splice_ext(void)
 {
 	VALUE mSplice = rb_define_module_under(rb_cIO, "Splice");
-	struct utsname utsname;
 
 	rb_define_singleton_method(rb_cIO, "splice", my_splice, -1);
 	rb_define_singleton_method(rb_cIO, "trysplice", trysplice, -1);
@@ -698,12 +716,7 @@ void Init_io_splice_ext(void)
 	 */
 	rb_define_const(mSplice, "MAX_AT_ONCE", SIZET2NUM(MAX_AT_ONCE));
 
-
-	if (uname(&utsname) == -1)
-		rb_sys_fail("uname");
-
-	/* includes 2.6.35-rc[1-6] */
-	if (strcmp(utsname.release, "2.6.35") >= 0) {
+	if (can_mod_pipe_size()) {
 		rb_define_method(rb_cIO, "pipe_size", pipe_size, 0);
 		rb_define_method(rb_cIO, "pipe_size=", set_pipe_size, 1);