adjust posix_spawn dup2 action behavior to match future requirements
the resolution to Austin Group issue #411 defined new semantics for
the posix_spawn dup2 file action in the (previously useless) case
where src and dest fd are equal. future issues will require the dup2
file action to remove the close-on-exec flag. without this change,
passing fds to a child with posix_spawn while avoiding fd-leak races
in a multithreaded parent required a complex dance with temporary fds.
based on patch by Petr Skocik. changes were made to preserve the
80-column formatting of the function and to remove code that became
unreachable as a result of the new functionality.
diff --git a/src/process/posix_spawn.c b/src/process/posix_spawn.c
index 0849c71..93fb155 100644
--- a/src/process/posix_spawn.c
+++ b/src/process/posix_spawn.c
@@ -27,12 +27,7 @@
#ifdef SYS_dup2
return __syscall(SYS_dup2, old, new);
#else
- if (old==new) {
- int r = __syscall(SYS_fcntl, old, F_GETFD);
- return r<0 ? r : old;
- } else {
- return __syscall(SYS_dup3, old, new, 0);
- }
+ return __syscall(SYS_dup3, old, new, 0);
#endif
}
@@ -109,8 +104,17 @@
__syscall(SYS_close, op->fd);
break;
case FDOP_DUP2:
- if ((ret=__sys_dup2(op->srcfd, op->fd))<0)
- goto fail;
+ fd = op->srcfd;
+ if (fd != op->fd) {
+ if ((ret=__sys_dup2(fd, op->fd))<0)
+ goto fail;
+ } else {
+ ret = __syscall(SYS_fcntl, fd, F_GETFD);
+ ret = __syscall(SYS_fcntl, fd, F_SETFD,
+ ret & ~FD_CLOEXEC);
+ if (ret<0)
+ goto fail;
+ }
break;
case FDOP_OPEN:
fd = __sys_open(op->path, op->oflag, op->mode);