On 2013-07-04 09:12:37 -0400, Andrew Dunstan wrote:
>
> On 07/04/2013 08:58 AM, Andres Freund wrote:
> >On 2013-07-04 08:50:34 -0400, Andrew Dunstan wrote:
> >>On 07/04/2013 08:31 AM, Michael Meskes wrote:
> >>>On Thu, Jul 04, 2013 at 07:58:39AM -0400, Andrew Dunstan wrote:
> >>>>>michael@feivel:~$ grep line test\\\\a/init.c |head -1
> >>>>>#line 1 "test\\a/init.pgc"
> >>>>...
> >>>>
> >>>>Really? I'd expect to see 4 backslashes in the #line directive, I think.
> >>>Eh, why? The four backslashes come are two that are escaped for shell usage.
> >>>The directory name is in my example was "test\\a". What did I miss?
> >>>
> >>Isn't the argument to #line a C string literal in which one would expect
> >>backslashes to be escaped? If not, how would it show a filename containing a
> >>'"' character?
> >>
> >> [andrew@emma inst.92.5701]$ bin/ecpg x\\\"a/y.pgc
> >> [andrew@emma inst.92.5701]$ grep line x\\\"a/y.c
> >> #line 1 "x\"a/y.pgc"
> >>
> >>This must surely be wrong.
> >I think it's correct. Quoting the gcc manual
> >(http://gcc.gnu.org/onlinedocs/gcc-4.8.1/cpp/Include-Syntax.html#Include-Syntax)
> >"However, if backslashes occur within file, they are considered ordinary
> >text characters, not escape characters. None of the character escape
> >sequences appropriate to string constants in C are processed. Thus,
> >#include "x\n\\y" specifies a filename containing three
> >backslashes. (Some systems interpret ‘\’ as a pathname separator. All of
> >these also interpret ‘/’ the same way. It is most portable to use only
> >‘/’.)"
>
> Well, that refers to #include, but for the sake of argument I'll assume the
> same rule applies to #line. So this just gets processed by stripping the
> surrounding quotes? Well I guess I learn something every day.
Gah. You're right. I only remembered the rules for #include and thought
that would be applicable. But:
http://gcc.gnu.org/onlinedocs/gcc-4.8.1/cpp/Line-Control.html#Line-Control :
»filename is interpreted according to the normal rules for a string
constant: backslash escapes are interpreted. This is different from
‘#include’.
Previous versions of CPP did not interpret escapes in ‘#line’; we have
changed it because the standard requires they be interpreted, and most
other compilers do.«
Greetings,
Andres Freund
-- Andres Freund http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
Services
