Re: apr_file_open() flag issue

[Jeff Trawick]

(I'm not subscribed to d...@perl...)

On Mon, Apr 20, 2009 at 6:18 PM, Marc Adkins <madk...@marchex.com> wrote:

>  I found this in mod_perl but the issue can be demonstrated without Perl.
>
> Attempting to open a file for append using the following flags:
>
> APR_BUFFERED | APR_BINARY | APR_CREATE | APR_APPEND
>
>
> will not work.  The apr_file_open() function returns APR_EACCES.  If the
> following flags are used:
>
>  APR_BUFFERED | APR_BINARY | APR_CREATE | APR_WRITE | APR_APPEND
>
>
> it works fine.  In a vacuum this behavior is debatable.  On the one hand,
> APR_APPEND could be seen to imply APR_WRITE.  On the other hand, it might
> be argued that the first case is incomplete flag-wise.
>
> In the context of Perl, however, particularly when using the APR PerlIO
> filter, this becomes problematic.  Perl uses special character sequences
> which are converted to the proper flags down underneath the covers.  So in
> Perl '>' (write to a new file) converts properly but '>>' (append to an
> existing file or create a new one if necessary) does not.  There is no
> message either, AFAIK, it just fails silently.
>

The Perl code that builds the apr_file_open() flags needs to turn on
APR_WRITE.

I think that this patch to mod_perl is what you need:

--- modperl_apr_perlio.c.orig    2007-12-31 02:39:50.000000000 -0500
+++ modperl_apr_perlio.c    2009-04-20 19:37:25.954107404 -0400
@@ -85,7 +85,7 @@

     switch (*mode) {
       case 'a':
-        apr_flag = APR_APPEND | APR_CREATE;
+        apr_flag = APR_WRITE | APR_CREATE | APR_APPEND;
         break;
       case 'w':
         apr_flag = APR_WRITE | APR_CREATE | APR_TRUNCATE;