[PATCH] fix test for vfork function

[Mark Salter]

A few places in the code check for existence of vfork by testing if
__NR_vfork is defined. Newer kernels don't have a vfork syscall in
which case, the library implements the vfork function using __NR_clone.

This patch adds a test for __UCLIBC_VFORK_USES_CLONE__ feature
definition which an architecture may define if vfork is implemented
using clone.

Signed-off-by: Mark Salter <msalter at redhat.com>
---
 libc/stdio/popen.c                                 |    2 +-
 libc/stdlib/system.c                               |    2 +-
 libc/stdlib/unix_grantpt.c                         |    2 +-
 libc/sysdeps/linux/c6x/bits/uClibc_arch_features.h |    3 +++
 4 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/libc/stdio/popen.c b/libc/stdio/popen.c
index d5c60cf..72ee60d 100644
--- a/libc/stdio/popen.c
+++ b/libc/stdio/popen.c
@@ -29,7 +29,7 @@
 
 /* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
 #include <sys/syscall.h>
-#if ! defined __NR_vfork
+#if ! defined __NR_vfork && ! defined __UCLIBC_VFORK_USES_CLONE__
 # define vfork fork
 # define VFORK_LOCK		((void) 0)
 # define VFORK_UNLOCK		((void) 0)
diff --git a/libc/stdlib/system.c b/libc/stdlib/system.c
index a92c307..cfea08e 100644
--- a/libc/stdlib/system.c
+++ b/libc/stdlib/system.c
@@ -26,7 +26,7 @@ extern __typeof(system) __libc_system;
 #if !defined __UCLIBC_HAS_THREADS_NATIVE__ || defined __sparc__
 /* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
 #include <sys/syscall.h>
-#ifndef __NR_vfork
+#if !defined __NR_vfork && !defined __UCLIBC_VFORK_USES_CLONE__
 # define vfork fork
 #endif
 
diff --git a/libc/stdlib/unix_grantpt.c b/libc/stdlib/unix_grantpt.c
index 1be0a7d..cba7fc9 100644
--- a/libc/stdlib/unix_grantpt.c
+++ b/libc/stdlib/unix_grantpt.c
@@ -33,7 +33,7 @@
 
 /* uClinux-2.0 has vfork, but Linux 2.0 doesn't */
 #include <sys/syscall.h>
-#if ! defined __NR_vfork
+#if ! defined(__NR_vfork) && ! defined(__NR_clone)
 #define vfork fork
 #endif
 
diff --git a/libc/sysdeps/linux/c6x/bits/uClibc_arch_features.h b/libc/sysdeps/linux/c6x/bits/uClibc_arch_features.h
index 59e7de9..936748a 100644
--- a/libc/sysdeps/linux/c6x/bits/uClibc_arch_features.h
+++ b/libc/sysdeps/linux/c6x/bits/uClibc_arch_features.h
@@ -45,4 +45,7 @@
 /* only weird assemblers generally need this */
 #define __UCLIBC_ASM_LINE_SEP__ @
 
+/* define if vfork function exists */
+#define __UCLIBC_VFORK_USES_CLONE__
+
 #endif /* _BITS_UCLIBC_ARCH_FEATURES_H */
-- 
1.7.9.1