Revamp the CLOEXEC support in Qt

The pipe2/dup3/accept4 functions and SOCK_CLOEXEC are quite old nowadays
on Linux. They were introduced on Linux 2.6.28 and glibc 2.10, all from
2008. They were also picked up by uClibc in 2011 and FreeBSD as of
version 10.0. So we no longer need the runtime detection of whether the
feature is available.

Instead, if the libc has support for it, use it unconditionally and fail
at runtime if the syscall isn't implemented.

Change-Id: Ib056b47dde3341ef9a52ffff13efcc39ef8dff7d
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

1 files changed, 17 insertions, 43 deletions

diff --git a/src/corelib/kernel/qcore_unix_p.h b/src/corelib/kernel/qcore_unix_p.h
index ce8d9f6d65..c744873fce 100644
--- a/src/corelib/kernel/qcore_unix_p.h
+++ b/src/corelib/kernel/qcore_unix_p.h
@@ -67,24 +67,6 @@
 
 struct sockaddr;
 
-#if defined(Q_OS_LINUX) && defined(O_CLOEXEC)
-# define QT_UNIX_SUPPORTS_THREADSAFE_CLOEXEC 1
-QT_BEGIN_NAMESPACE
-namespace QtLibcSupplement {
-    inline int accept4(int, sockaddr *, QT_SOCKLEN_T *, int)
-    { errno = ENOSYS; return -1; }
-    inline int dup3(int, int, int)
-    { errno = ENOSYS; return -1; }
-    inline int pipe2(int [], int )
-    { errno = ENOSYS; return -1; }
-}
-QT_END_NAMESPACE
-using namespace QT_PREPEND_NAMESPACE(QtLibcSupplement);
-
-#else
-# define QT_UNIX_SUPPORTS_THREADSAFE_CLOEXEC 0
-#endif
-
 #define EINTR_LOOP(var, cmd)                    \
     do {                                        \
         var = cmd;                              \
@@ -181,16 +163,12 @@ static inline int qt_safe_pipe(int pipefd[2], int flags = 0)
 {
     Q_ASSERT((flags & ~O_NONBLOCK) == 0);
 
-    int ret;
-#if QT_UNIX_SUPPORTS_THREADSAFE_CLOEXEC && defined(O_CLOEXEC)
+#ifdef QT_THREADSAFE_CLOEXEC
     // use pipe2
     flags |= O_CLOEXEC;
-    ret = ::pipe2(pipefd, flags); // pipe2 is Linux-specific and is documented not to return EINTR
-    if (ret == 0 || errno != ENOSYS)
-        return ret;
-#endif
-
-    ret = ::pipe(pipefd);
+    return ::pipe2(pipefd, flags); // pipe2 is documented not to return EINTR
+#else
+    int ret = ::pipe(pipefd);
     if (ret == -1)
         return -1;
 
@@ -204,6 +182,7 @@ static inline int qt_safe_pipe(int pipefd[2], int flags = 0)
     }
 
     return 0;
+#endif
 }
 
 #endif // Q_OS_VXWORKS
@@ -213,22 +192,19 @@ static inline int qt_safe_dup(int oldfd, int atleast = 0, int flags = FD_CLOEXEC
 {
     Q_ASSERT(flags == FD_CLOEXEC || flags == 0);
 
-    int ret;
 #ifdef F_DUPFD_CLOEXEC
-    // use this fcntl
-    if (flags & FD_CLOEXEC) {
-        ret = ::fcntl(oldfd, F_DUPFD_CLOEXEC, atleast);
-        if (ret != -1 || errno != EINVAL)
-            return ret;
-    }
-#endif
-
+    int cmd = F_DUPFD;
+    if (flags & FD_CLOEXEC)
+        cmd = F_DUPFD_CLOEXEC;
+    return ::fcntl(oldfd, cmd, atleast);
+#else
     // use F_DUPFD
-    ret = ::fcntl(oldfd, F_DUPFD, atleast);
+    int ret = ::fcntl(oldfd, F_DUPFD, atleast);
 
     if (flags && ret != -1)
         ::fcntl(ret, F_SETFD, flags);
     return ret;
+#endif
 }
 
 // don't call dup2
@@ -238,14 +214,11 @@ static inline int qt_safe_dup2(int oldfd, int newfd, int flags = FD_CLOEXEC)
     Q_ASSERT(flags == FD_CLOEXEC || flags == 0);
 
     int ret;
-#if QT_UNIX_SUPPORTS_THREADSAFE_CLOEXEC && defined(O_CLOEXEC)
+#ifdef QT_THREADSAFE_CLOEXEC
     // use dup3
-    if (flags & FD_CLOEXEC) {
-        EINTR_LOOP(ret, ::dup3(oldfd, newfd, O_CLOEXEC));
-        if (ret == 0 || errno != ENOSYS)
-            return ret;
-    }
-#endif
+    EINTR_LOOP(ret, ::dup3(oldfd, newfd, flags ? O_CLOEXEC : 0));
+    return ret;
+#else
     EINTR_LOOP(ret, ::dup2(oldfd, newfd));
     if (ret == -1)
         return -1;
@@ -253,6 +226,7 @@ static inline int qt_safe_dup2(int oldfd, int newfd, int flags = FD_CLOEXEC)
     if (flags)
         ::fcntl(newfd, F_SETFD, flags);
     return 0;
+#endif
 }
 
 static inline qint64 qt_safe_read(int fd, void *data, qint64 maxlen)