Code Question in FAT Filesystem

[Arnout Vandecappelle]

 I agree that const char * const is most likely the intended declaration.

 By the way, in C90 repeating the const is illegal as well.  I don't know why they suddenly allowed it in C99 (but not C++)...

 Regards,
 Arnout

On Monday 23 August 2010 21:35:01, Somervill, Kevin M. (LARC-D203) wrote:
> I think the issue is the "const char const" that Joel originally posted.  The declaration "const char * const foo" is not the same as "const char const * foo".  In the latter, I believe both const qualifiers are associated with the char.  It looks like this format is left over from K&R C, but "const char *" and "char const *" seem to be equivalent.  Also, gcc will allow you to use as many const qualifiers as you like (eg. "const const const char stupid;" will compile using gcc but not g++).
> 
> From the original email, you probably should swap the second const and the * to read "const char * const" so that neither the variable (MSDOS_DOT_NAME) nor the location (*MSDOS_DOT_NAME) can be changed. Perhaps like:
> 
> msdos.h:extern const char * const MSDOS_DOT_NAME;    /* ".", padded to MSDOS_NAME chars */ 
> 
> IMO.
> 
> ./ks
> 
> | -----Original Message-----
> | From: rtems-users-bounces at rtems.org [mailto:rtems-users-bounces at rtems.org] On
> | Behalf Of Eric Norum
> | Sent: Monday, August 23, 2010 2:30 PM
> | To: Joel Sherrill
> | Cc: rtems-users at rtems.org
> | Subject: Re: Code Question in FAT Filesystem
> | 
> | I'm no expert on C++, but for C at least, I don't see any type qualifier being
> | specified more than once:
> | 	const char *const foo
> | declares foo to be a constant pointer to constant character(s)
> | 
> | This is different than
> | 	const *bar
> | which declares bar as a mutable pointer to constant character(s)
> | 
> | or
> | 	char *const bletch
> | which declares bletch as a constant pointer to mutable character(s)
> | 
> | So, with these declarations:
> | 	1) bletch could never appear as an lvalue, but *bletch could
> | 	2) *bar could never appear as an lvalue, but bar could
> | 	2) foo could never appear as an lvalue nor could *foo appear as an
> | lvalue
> | 
> | FWIW.
> | 
> | On Aug 23, 2010, at 11:20 AM, Joel Sherrill wrote:
> | 
> | > Hi,
> | >
> | > I came across this while trying to review
> | > Coverity output.
> | >
> | > [joel at iceland dosfs]$ grep "const char const" *
> | > msdos.h:extern const char const* MSDOS_DOT_NAME;    /* ".", padded to
> | MSDOS_NAME chars */
> | > msdos.h:extern const char const* MSDOS_DOTDOT_NAME; /* ".", padded to
> | MSDOS_NAME chars */
> | > msdos_misc.c:const char const* MSDOS_DOT_NAME    = ".          ";
> | > msdos_misc.c:const char const* MSDOS_DOTDOT_NAME = "..         ";
> | >
> | > My understanding is that this is legal in C99 and
> | > illegal in C++.
> | >
> | > Coverity complains it is ...
> | >
> | > *dupl_type_qualifier*: type qualifier specified more than once
> | >
> | >
> | > Would it be OK to change these to "const char *MSDOS_DOT_"?
> | >
> | > --
> | > Joel Sherrill, Ph.D.             Director of Research&  Development
> | > joel.sherrill at OARcorp.com        On-Line Applications Research
> | > Ask me about RTEMS: a free RTOS  Huntsville AL 35805
> | >   Support Available             (256) 722-9985
> | >
> | >
> | > _______________________________________________
> | > rtems-users mailing list
> | > rtems-users at rtems.org
> | > http://www.rtems.org/mailman/listinfo/rtems-users
> | 
> | --
> | Eric Norum
> | wenorum at lbl.gov
> | 
> | 
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-- 
Arnout Vandecappelle                               arnout at mind be
Senior Embedded Software Architect                 +32-16-286540
Essensium/Mind                                     http://www.mind.be
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