[Bug preprocessor/22168] New: #if #A == #B should have a diagnostic

[Bug preprocessor/22168] New: #if #A == #B should have a diagnostic

[geoffk at gcc dot gnu dot org]

GCC quietly accepts the following:

#define A a
#define B a
#if #A == #B
#endif

but it should not, because '#A == #B' is not an integer constant expression, see C99 section 6.10.1 
paragraph 1.  GCC does properly diagnose

#if "a" == "a"

-- 
           Summary: #if #A == #B should have a diagnostic
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Keywords: accepts-invalid
          Severity: normal
          Priority: P3
         Component: preprocessor
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: geoffk at gcc dot gnu dot org
                CC: dje at gcc dot gnu dot org,gcc-bugs at gcc dot gnu dot
                    org
 GCC build triplet: *
  GCC host triplet: *-*-*
GCC target triplet: *


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic

[schwab at suse dot de]

------- Additional Comments From schwab at suse dot de  2005-06-24 09:06 -------
GCC should already reject the use of the # operator, which is only allowed in 
the replacement list of a macro and then only when followed by a macro 
parameter. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic

[neil at gcc dot gnu dot org]

------- Additional Comments From neil at gcc dot gnu dot org  2005-06-24 14:56 -------
Documented behaviour.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic

[geoffk at gcc dot gnu dot org]

------- Additional Comments From geoffk at gcc dot gnu dot org  2005-06-24 15:19 -------
Still a bug, even if a documented one; the syntax does not allow it.  '#if #A' is neither an if-group (because 
'#A' is not syntactically a constant-expression in the preprocessor) nor a sequence of group-parts, 
because 'if' is not a non-directive; see 6.10 paragraph 1.  Since this a syntax violation, a diagnostic is 
required.

Where is it documented?

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic

[schwab at suse dot de]

------- Additional Comments From schwab at suse dot de  2005-06-24 15:26 -------
*Note (cpp)Assertions::. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic

[pinskia at physics dot uc dot edu]

------- Additional Comments From pinskia at physics dot uc dot edu  2005-06-24 15:42 -------
Subject: Re:  New: #if #A == #B should have a diagnostic


On Jun 23, 2005, at 10:04 PM, geoffk at gcc dot gnu dot org wrote:

> GCC quietly accepts the following:
>
> #define A a
> #define B a
> #if #A == #B
> #endif

In fact if we look at the output for the following code:
#define A b
#define B c
#if #A == #B
void g(void);
#endif

We find that "void g(void);" is always outputted so in fact
it does not do what David wanted it to do.

Thanks,
Andrew Pinski



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

Re: [Bug preprocessor/22168] New: #if #A == #B should have a diagnostic

[Andrew Pinski]

On Jun 23, 2005, at 10:04 PM, geoffk at gcc dot gnu dot org wrote:

> GCC quietly accepts the following:
>
> #define A a
> #define B a
> #if #A == #B
> #endif

In fact if we look at the output for the following code:
#define A b
#define B c
#if #A == #B
void g(void);
#endif

We find that "void g(void);" is always outputted so in fact
it does not do what David wanted it to do.

Thanks,
Andrew Pinski

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[geoffk at gcc dot gnu dot org]

------- Additional Comments From geoffk at gcc dot gnu dot org  2005-06-24 18:02 -------
Yup, it's documented.  However, it's still silently accepted even with -pedantic, and the language doesn't 
permit that.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|#if #A == #B should have a  |#if #A == #B should have a
                   |diagnostic                  |diagnostic in ISO C mode


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[neil at gcc dot gnu dot org]

------- Additional Comments From neil at gcc dot gnu dot org  2005-06-24 22:24 -------
(In reply to comment #6)
> Yup, it's documented.  However, it's still silently accepted even with
-pedantic, and the language doesn't 
> permit that.

My copy of the standard only requires a constant expression - can you point out
where you read its requiring an integer constant expression?

The standard explicitly permits extensions to constant expressions.  Since this
extension is explicitly documented as for use in #if expressions, it should be
obvious that we intend #foo as a constant expression.  No diagnostic is
therefore required.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-06-24 22:26:42
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[schwab at suse dot de]

------- Additional Comments From schwab at suse dot de  2005-06-24 22:41 -------
The standard does not allow to extend the syntax.  Since this violates the 
syntax of the language a diagnostic is required. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[joseph at codesourcery dot com]

------- Additional Comments From joseph at codesourcery dot com  2005-06-24 23:09 -------
Subject: Re:  #if #A == #B should have a diagnostic
 in ISO C mode

On Fri, 24 Jun 2005, neil at gcc dot gnu dot org wrote:

> My copy of the standard only requires a constant expression - can you point out
> where you read its requiring an integer constant expression?

6.10.1#1, "shall be an integer constant expression"; 6.8.1 in C90.

> The standard explicitly permits extensions to constant expressions.  Since this

But not to integer constant expressions (at least according to the view 
expressed in the DR#312 discussion in the draft Lillehammer minutes, 
although DR#032 implies a different view).



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[jsm28 at gcc dot gnu dot org]

------- Additional Comments From jsm28 at gcc dot gnu dot org  2005-06-25 22:11 -------
Diagnostic needed for -pedantic (and in general I don't like extensions not
being diagnosed with -pedantic even where diagnostics aren't strictly required).

[comment#10 did not appear on gcc-bugs - apparently substantive messages should
not be sent to gcc-bugzilla with signatures or other attachments.]


-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
OtherBugsDependingO|                            |16620, 16989
              nThis|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[tromey at gcc dot gnu dot org]

------- Comment #18 from tromey at gcc dot gnu dot org  2008-05-13 15:20 -------
Fixed on trunk.
I think we're unlikely to backport this, so I'm closing it.


-- 

tromey at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[tromey at gcc dot gnu dot org]

------- Comment #17 from tromey at gcc dot gnu dot org  2008-05-13 14:51 -------
Subject: Bug 22168

Author: tromey
Date: Tue May 13 14:50:27 2008
New Revision: 135264

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=135264
Log:
libcpp
        PR preprocessor/22168:
        * include/cpplib.h (struct cpp_options) <objc>: Update
        documentation.
        * expr.c (eval_token): Warn for use of assertions.
        * directives.c (directive_diagnostics): Warn about extensions.
        (DEPRECATED): New define.
        (DIRECTIVE_TABLE): Use it.
gcc
        PR preprocessor/22168:
        * doc/cpp.texi (Top): Update menu.
        (Alternatives to Wrapper #ifndef): New node.
        (Other Directives): Document deprecation.
        (Obsolete Features): Remove menu.
        (Assertions): Merge node into Obsolete Features.
        (Obsolete once-only headers): Move earlier; rename to Alternatives
        to Wrapper #ifndef.
        * doc/cppopts.texi: Update.
        * c.opt (Wdeprecated): Enable for C and ObjC.
        * doc/invoke.texi (Option Summary): Move -Wno-deprecated.
        (C++ Dialect Options): Move -Wno-deprecated from here to...
        (Warning Options): ... here.
gcc/testsuite
        PR preprocessor/22168:
        * gcc.dg/pch/import-2.hs: Add -Wno-deprecated.
        * gcc.dg/pch/import-1.hs: Add -Wno-deprecated.
        * gcc.dg/pch/import-2.c: Add -Wno-deprecated.
        * gcc.dg/pch/import-1.c: Add -Wno-deprecated.
        * gcc.dg/cpp/import2.c: Add -Wno-deprecated.
        * gcc.dg/cpp/import1.c: Add -Wno-deprecated.
        * gcc.dg/cpp/trad/assert3.c: Add -Wno-deprecated.
        * gcc.dg/cpp/trad/assert2.c: Add -Wno-deprecated.
        * gcc.dg/cpp/trad/assert1.c: Add -Wno-deprecated.
        * gcc.dg/cpp/ident.c: Add -Wno-deprecated.
        * gcc.dg/cpp/ident-1.c: Add -Wno-deprecated.
        * gcc.dg/cpp/extratokens.c: Add -Wno-deprecated.
        * gcc.dg/cpp/assert3.c: Add -Wno-deprecated.
        * gcc.dg/cpp/assert2.c: Add -Wno-deprecated.
        * gcc.dg/cpp/assert1.c: Add -Wno-deprecated.
        * gcc.dg/cpp/assert4.c: Compile with -ansi and not -pedantic.  Add
        -Wno-deprecated.
        * gcc.dg/cpp/pr22168.c: New file.
        * gcc.dg/cpp/pr22168-2.c: New file.

Added:
    trunk/gcc/testsuite/gcc.dg/cpp/pr22168-2.c
    trunk/gcc/testsuite/gcc.dg/cpp/pr22168.c
Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/c.opt
    trunk/gcc/doc/cpp.texi
    trunk/gcc/doc/cppopts.texi
    trunk/gcc/doc/invoke.texi
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/gcc.dg/cpp/assert1.c
    trunk/gcc/testsuite/gcc.dg/cpp/assert2.c
    trunk/gcc/testsuite/gcc.dg/cpp/assert3.c
    trunk/gcc/testsuite/gcc.dg/cpp/assert4.c
    trunk/gcc/testsuite/gcc.dg/cpp/extratokens.c
    trunk/gcc/testsuite/gcc.dg/cpp/ident-1.c
    trunk/gcc/testsuite/gcc.dg/cpp/ident.c
    trunk/gcc/testsuite/gcc.dg/cpp/import1.c
    trunk/gcc/testsuite/gcc.dg/cpp/import2.c
    trunk/gcc/testsuite/gcc.dg/cpp/trad/assert1.c
    trunk/gcc/testsuite/gcc.dg/cpp/trad/assert2.c
    trunk/gcc/testsuite/gcc.dg/cpp/trad/assert3.c
    trunk/gcc/testsuite/gcc.dg/pch/import-1.c
    trunk/gcc/testsuite/gcc.dg/pch/import-1.hs
    trunk/gcc/testsuite/gcc.dg/pch/import-2.c
    trunk/gcc/testsuite/gcc.dg/pch/import-2.hs
    trunk/libcpp/ChangeLog
    trunk/libcpp/directives.c
    trunk/libcpp/expr.c
    trunk/libcpp/include/cpplib.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[tromey at gcc dot gnu dot org]

------- Comment #16 from tromey at gcc dot gnu dot org  2008-02-26 20:48 -------
*** Bug 35312 has been marked as a duplicate of this bug. ***


-- 

tromey at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |neil at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[manu at gcc dot gnu dot org]

------- Comment #15 from manu at gcc dot gnu dot org  2007-05-21 09:54 -------
*** Bug 11051 has been marked as a duplicate of this bug. ***


-- 

manu at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |bangerth at dealii dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[tromey at gcc dot gnu dot org]

-- 

tromey at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |tromey at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2006-01-21 03:03:43         |2007-01-08 01:32:48
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[patchapp at dberlin dot org]

------- Comment #14 from patchapp at dberlin dot org  2007-01-01 21:57 -------
Subject: Bug number PR preprocessor/22168

A patch for this bug has been added to the patch tracker.
The mailing list url for the patch is
http://gcc.gnu.org/ml/gcc-patches/2006-12/msg01853.html


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168

[Bug preprocessor/22168] #if #A == #B should have a diagnostic in ISO C mode

[tromey at gcc dot gnu dot org]

------- Comment #13 from tromey at gcc dot gnu dot org  2006-12-29 02:54 -------
I am testing a patch for this.

It pedwarns on '#foo' in an expression, and also when #assert or
#unassert is used.  It also warns about these when -Wdeprecated
is given.


-- 

tromey at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |tromey at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22168