gawk 3.1.4: reproducible hang, regression from 3.1.3

[James Troup]

Hi,

A Debian user reported[0] gawk 3.1.4 broke a (relatively) complex
program that makes extensive use of awk, called 'apt-move'.  I finally
managed to reduced the problem down to a 3 line test case, enclosed
below[1].

I believe the problem comes from the following code, introduced in
3.1.4:

[io.c, line 560]
|       for (rp = red_head; rp != NULL; rp = rp->next) {
|               if ((rp->flag & RED_EOF) && tree->type == Node_redirect_pipein) 
{
|                       if (rp->pid != -1)
|                               wait_any(0);
|               }

The problem is that, if we have an existing redirect which is a simple
file redirect[b] and it's hit EOF and we try to create a new '|'
redirect[c], this new code will try to wait(2) and if there are any
other redirects which _did_ spawn a child (like [a]) the wait() will
hang indefinitely waiting for it to exit.

Hope that makes sense :)

-- 
James

[0] http://bugs.debian.org/263964

[1] 
================================================================================
#!/usr/bin/gawk -f

BEGIN {
        printf "" | "cat"             # [a]
        getline line < "/dev/null"    # [b]
        "true" | getline line         # [c]
}
================================================================================