svn commit: trunk/busybox/docs/busybox.net

[landley at busybox.net]

Author: landley
Date: 2006-01-28 22:45:38 -0800 (Sat, 28 Jan 2006)
New Revision: 13651

Log:
Remind me to implement bb_fork_exec()...


Modified:
   trunk/busybox/docs/busybox.net/programming.html


Changeset:
Modified: trunk/busybox/docs/busybox.net/programming.html
===================================================================
--- trunk/busybox/docs/busybox.net/programming.html	2006-01-29 06:29:01 UTC (rev 13650)
+++ trunk/busybox/docs/busybox.net/programming.html	2006-01-29 06:45:38 UTC (rev 13651)
@@ -235,6 +235,12 @@
 
 <h2><a name="tips_vfork">Fork and vfork</a></h2>
 
+<p>Busybox hides the difference between fork() and vfork() in
+libbb/bb_fork_exec.c.  If you ever want to fork and exec, use bb_fork_exec()
+(which returns a pid and takes the same arguments as execve(), although in
+this case envp can be NULL) and don't worry about it.  This description is
+here in case you want to know why that does what it does.</p>
+
 <p>On systems that haven't got a Memory Management Unit, fork() is unreasonably
 expensive to implement, so a less capable function called vfork() is used
 instead.</p>
@@ -277,6 +283,11 @@
 sharing the same memory without stomping all over each other.  As soon as
 the child calls exec(), the parent resumes.</p>
 
+<p>If the child's attempt to call exec() fails, the child should call _exit()
+rather than a normal exit().  This avoids any atexit() code that might confuse
+the parent.  (The parent should never call _exit(), only a vforked child that
+failed to exec.)</p>
+
 <p>(Now in theory, a nommu system could just copy the _stack_ when it forks
 (which presumably is much shorter than the heap), and leave the heap shared.
 In practice, you've just wound up in a multi-threaded situation and you can't