Re: debug/2714

[James Cownie <jcownie at etnus dot com>]

The following reply was made to PR debug/2714; it has been noted by GNATS.

From: James Cownie <jcownie@etnus.com>
To: gcc-gnats@gcc.gnu.org, gcc-prs@gcc.gnu.org, jcownie@etnus.com,
 	gcc-bugs@gcc.gnu.org, dje@gcc.gnu.org, chan1@llnl.gov
Cc:  
Subject: Re: debug/2714
Date: Mon, 03 Dec 2001 11:10:11 +0000

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&pr=2714&database=gcc
 
 I don't know what happened to this mail, but clearly it never got to you,
 so here it is again...
 
 -- Jim
 
 To: dje@gcc.gnu.org
 cc: chan1@llnl.gov, gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org
 Subject: Re: debug/2714: Stabs truncated on AIX 
 In-reply-to: Your message of "10 Aug 2001 22:20:35 -0000."
              <20010810222035.19493.qmail@sourceware.cygnus.com> 
 Date: Tue, 04 Sep 2001 11:54:23 +0100
 From: James Cownie <jcownie@pc2>
 
 Now that I'm back from my holiday I can answer in a little more
 detail.
 
 >     AIX assembly language does not have a line continuation
 >     character.  Neither "?" nor " ?" before a newline or on the
 >     next line continues the string.  All variants produce syntax
 >     errors from the AIX Assembler.  The continuation character
 >     is not documented in the AIX Assembler manual nor mentioned
 >     in the AIX Assembler source code.  Is this a GNU Assembler
 >     feature?  From where does your recommendation of a "?"
 >     continuation character derive?
 > 
 > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=2714&database=gcc
 
 I think you are mis-understanding the point. The point is not to get
 the assembler to generate a single long string, but rather to have gcc
 generate multiple stabs _each_ of which has a string, but which obey
 the stab syntax for continued strings. As far as the assembler is
 concerned there is no continued string, it just sees a whole bunch of
 stab directives, however a debugger understands the internal syntax of
 the strings, and therefore realises that the multiple stabs really
 represent a single, long, stab string.
 
 gcc already understands how to generate continued stabs, and the patch
 I suggested just enables that behaviour, whereas the default AIX
 configuration of gcc is to assume that the assembler can handle an
 infinitely long string (which, as we have seen it can't).
 
 The recommendation for using a '?' continuation comes from
 
   http://www.austin.ibm.com/doc_link/en_US/a_doc_lib/files/aixfiles/XCOFF.htm#JTSCi131jbau
 
 which says :-
 
   Stabstring Grammar
 
   ... elided ...
 
   Long stabstrings can be split across multiple symbol table entries
   for easier handling. In the stabstring grammar, a # (pound sign)
   indicates a point at which a stabstring may be continued. A
   continuation is indicated by using either the ? (question mark) or \
   as the last character in the string. The next part of the stabstring
   is in the name of the next symbol table entry. If an alternative for
   a production is empty, the grammar shows the keyword /*EMPTY*/.
 
 Since it also allows \ that may be easier, I recommended ?, since
 that is what the IBM compilers use...
 
 Enjoy
 
 -- Jim 
 
 James Cownie	<jcownie@etnus.com>
 Etnus, LLC.     +44 117 9071438
 http://www.etnus.com