* io.c (linux_iocparm_len): enable only exist _IOC_SIZE().

  Because musl libc doesn't have it. [Bug #8051] [ruby-core:53229]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39818 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 2 deletions

diff --git a/io.c b/io.c
index eb8b80c63b..cc91f7b51c 100644
--- a/io.c
+++ b/io.c
@@ -8473,7 +8473,7 @@ do_ioctl(int fd, ioctl_req_t cmd, long narg)
 
 #define DEFULT_IOCTL_NARG_LEN (256)
 
-#ifdef __linux__
+#if defined(__linux__) && defined(_IOC_SIZE)
 static long
 linux_iocparm_len(ioctl_req_t cmd)
 {
@@ -8506,7 +8506,7 @@ ioctl_narg_len(ioctl_req_t cmd)
 #endif
 #ifdef IOCPARM_LEN
     len = IOCPARM_LEN(cmd);	/* on BSDish systems we're safe */
-#elif defined(__linux__)
+#elif defined(__linux__) && defined(_IOC_SIZE)
     len = linux_iocparm_len(cmd);
 #else
     /* otherwise guess at what's safe */