Re: bin/39135: /usr/bin/awk: printf supports extra- (and broken) formatting rules

["Greg A. Woods; Planix, Inc." <woods%planix.ca@localhost>]

The following reply was made to PR bin/39135; it has been noted by GNATS.

From: "Greg A. Woods; Planix, Inc." <woods%planix.ca@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: 
Subject: Re: bin/39135: /usr/bin/awk: printf supports extra- (and broken) 
formatting rules
Date: Sun, 13 Jul 2008 13:03:17 -0400

 On 12-Jul-08, at 1:30 PM, David Laight wrote:
 >
 > On Sat, Jul 12, 2008 at 04:00:06PM +0000, Greg A. Woods; Planix,  
 > Inc. wrote:
 >> The following reply was made to PR bin/39135; it has been noted by  
 >> GNATS.
 >>
 >> From: "Greg A. Woods; Planix, Inc." <woods%planix.ca@localhost>
 >> To: gnats-bugs%NetBSD.org@localhost
 >> Cc:
 >> Subject: Re: bin/39135: /usr/bin/awk: printf supports extra- (and  
 >> broken) formatting rules
 >> Date: Sat, 12 Jul 2008 11:58:12 -0400
 >>
 >> On 11-Jul-08, at 8:35 PM, cheusov%tut.by@localhost wrote:
 >>
 >>> awk 'BEGIN {printf "%llu\n", 123}'
 >>
 >>
 >> Hah!  Interesting side effect of directly using printf(3)!  ;-)
 >
 > So using %n will have interesting effects ...
 
 
 Not so much.  I goofed in remembering how much of the formatting was  
 handed off to libc.  It's actually sprintf(3) that's used to format  
 numbers, and only after all the '%' syntax in the format string has  
 (supposedly) been decoded for the most part.  "%n" isn't directly  
 supported.  See run.c:format() and the following example.
 
        $ awk 'BEGIN {printf "%n\n", 123}'
        awk: weird printf conversion %n
         source line number 1
        %n123
 
 I'm still not sure what exactly is wrong with AWK's use of sprintf()  
 -- on first glance I would have thought that the "long long" flag  
 should already be ignored, though on closer examination it seems any  
 number of length flags will be skipped over _and_ preserved and passed  
 to sprintf():
 
        $ awk 'BEGIN {printf "%llllld\n", 123}'
        578115701986820219
        $ awk 'BEGIN {printf "%#0lllllx\n", 123}'
        0x805e12b0000007b
 
 Perhaps the code from printf(1) [which seems to get this stuff right]  
 could be enhanced to match AWK's requirements and then be used to  
 replace the existing format() function.
 
 On the other hand fixing the isalfpha() && != 'l' && != 'h' && != 'L'  
 test to be much more stringent  (in the manner of how printf(1) does  
 it) would perhaps be the least intrusive fix.
 
 -- 
                                        Greg A. Woods; Planix, Inc.
                                        <woods%planix.ca@localhost>