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Re: bison-1.875: g++ and __attribute__ line

From: Nelson H. F. Beebe
Subject: Re: bison-1.875: g++ and __attribute__ line
Date: Fri, 3 Jan 2003 18:38:10 -0700 (MST)

I reported about a problem with bison-1.875-generated code under g++

> An additional check in the installed yacc.c file is needed:
>       #if defined (__GNUC_MINOR__) && 2093 <= (__GNUC__ * 1000 + 
> __GNUC_MINOR__) && !define(__GNUG__)
> but perhaps there is a cleaner way.

Paul Eggert responsed:

>> ...
>> Won't it suffice to append a semicolon to the __attribute__ line, as
>> in the patch I sent you earlier today?
>> ...

Not quite: g++ then complains:

    y.tab.c:2677:warning: empty declaration

Although it is just a warning, it is an unwanted message, and it could
well become an error with the next gcc release.  The gcc manual says:

>> ...
>>    The keyword `__attribute__' allows you to specify special attributes
>> when making a declaration.  This keyword is followed by an attribute
>> specification inside double parentheses.  The following attributes are
>> currently defined for functions on all targets: `noreturn', `noinline',
                     ^^^^^^^^^^^^^-- note
>> `always_inline', `pure', `const', `format', `format_arg',
>> `no_instrument_function', `section', `constructor', `destructor',
>> `used', `unused', `deprecated', `weak', `malloc', and `alias'.
>> ...

The use that bison is making of this is not for functions:

  goto yyerrlab2;
  __attribute__ ((__unused__))
  goto yyerrlab2;

It seems to me that this is in disagreement with the documented
purpose of __attribute__(()), and thus, should be taken out, or
rewritten to be conformant.

- Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
- Center for Scientific Computing       FAX: +1 801 581 4148                  -
- University of Utah                    Internet e-mail: address@hidden  -
- Department of Mathematics, 110 LCB        address@hidden  address@hidden -
- 155 S 1400 E RM 233                       address@hidden                    -
- Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe  -

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