os.execute() side effect for signal handling

[Michal Kolodziejczyk <miko@...>]

Hello,
consider those 2 lua programs:

while true do end

and

while true do os.execute() end

When run from the standard lua interpreter, the first one can be stopped
by pressing CTRL+C (sending SIGINT), while the second one cannot.

The reason is that os.execute() calls system(), and my manual page for
system() says:
"During execution  of the command, SIGCHLD will be blocked, and SIGINT
and SIGQUIT will be ignored."

and also:

"As  mentioned, system() ignores SIGINT and SIGQUIT.  This may make pro‐
 grams that call it from a loop uninterruptible, unless they  take  care
 themselves to check the exit status of the child.  E.g.

 while (something) {
   int ret = system("foo");

   if (WIFSIGNALED(ret) &&
     (WTERMSIG(ret) == SIGINT || WTERMSIG(ret) == SIGQUIT))
       break;
 }"

So, either this side effect should be mentioned in Lua reference manual
for os.execute() (so the equivalent program snippet would be
"ret=os.execute(); if ret>0 then os.exit(ret) end"), or os.execute()
should check for the return code itself and call exit() for SIGINT/SIGQUIT.

Regards,
miko