Re: preprocessor/6781: Creating header-names is not possible

Re: preprocessor/6781: Creating header-names is not possible

[Martin v. Löwis]

The following reply was made to PR preprocessor/6781; it has been noted by GNATS.

From: loewis@informatik.hu-berlin.de (Martin v. =?iso-8859-1?q?L=F6wis?=)
To: neil@gcc.gnu.org
Cc: gcc-bugs@gcc.gnu.org, gcc-prs@gcc.gnu.org, gcc-gnats@gcc.gnu.org
Subject: Re: preprocessor/6781: Creating header-names is not possible
Date: 23 May 2002 16:16:17 +0200

 neil@gcc.gnu.org writes:
 
 >     Sorry, my mistake.
 >     
 >     #define inc2(a,b) <a.b>
 >     
 >     should work I think.
 
 That works fine indeed.
 
 Thanks,
 Martin

Re: preprocessor/6781: Creating header-names is not possible

[neil]

Synopsis: Creating header-names is not possible

State-Changed-From-To: feedback->closed
State-Changed-By: neil
State-Changed-When: Thu May 23 09:38:24 2002
State-Changed-Why:
    Can be done in a different way.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6781

Re: preprocessor/6781: Creating header-names is not possible

[neil]

Synopsis: Creating header-names is not possible

State-Changed-From-To: closed->feedback
State-Changed-By: neil
State-Changed-When: Thu May 23 03:53:55 2002
State-Changed-Why:
    Sorry, my mistake.
    
    #define inc2(a,b) <a.b>
    
    should work I think.
    
    Neil.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6781

Re: preprocessor/6781: Creating header-names is not possible

[neil]

Synopsis: Creating header-names is not possible

State-Changed-From-To: open->closed
State-Changed-By: neil
State-Changed-When: Thu May 23 03:49:32 2002
State-Changed-Why:
    I have no intention of changing this behaviour (the
    diagnostic in your other PR excepted).
    
    The correct fix is for you to do you the correct and
    portable macro
    
    #define inc2(a,b) <a.##b>
    
    and everything should work.  If it doesn't, let me know.

http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6781

preprocessor/6781: Creating header-names is not possible

[loewis]

>Number:         6781
>Category:       preprocessor
>Synopsis:       Creating header-names is not possible
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          change-request
>Submitter-Id:   net
>Arrival-Date:   Thu May 23 03:26:00 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator:     
>Release:        3.1
>Organization:
HUB
>Environment:
System: SunOS paros 5.9 Beta_Refresh sun4u sparc SUNW,Sun-Blade-1000
Architecture: sun4

	
host: sparc-sun-solaris2.8
build: sparc-sun-solaris2.8
target: sparc-sun-solaris2.8
configured with: ../configure --host=sparc-sun-solaris2.8 --enable-shared --enable-threads --with-cpu=v8 --with-gnu-ld --with-gnu-as --enable-version-specific-runtime-libs
>Description:
	The code

#define inc2(a,b) <##a##.##b##>
#define INC(X) inc2(X,h)
#include INC(stdio)

int main()
{
  printf("Hallo");
}

	first gives a warning, then reports

	stdio: No such file or directory

The intent of this code is to create a header-name token (2.8)
through token pasting. In an pedantic interpretation, this invokes
undefined behaviour, since it creates intermediate tokens which are
invalid preprocessing tokens.

GCC should support this code as an extension (performing an #include
of stdio.h), and only warn about this problem when pedantic (since it
is undefined behaviour, no diagnostics is required by the standard).
More specifically, it normally should only emit the warning if 
interpreting the full ## sequence produces an invalid token.

Havin this extension is desirable, because
a) nearly every other compiler supports it (even though just because
   the compilers fail to notice the problem);
b) this is the best approach to deal with portability of CORBA applications,
   where different IDL compilers emit differently named header files.
    

>How-To-Repeat:
	Compile the included program.
>Fix:
	
>Release-Note:
>Audit-Trail:
>Unformatted: