C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  layout-compatible types and value representations          C++Talk.NET Forum Index -> C++ language, library and standards View previous topic :: View next topic   Author Message Michael Norrish Guest Posted: Wed Apr 05, 2006 4:06 pm    Post subject: layout-compatible types and value representations Does the standard allow int * and unsigned * to have different value representations and alignment requirements? The language in the last sentence of 3.9.2 para 3 only requires identical representations and alignments where the types pointed at are "layout compatible". It seems that the only places were layout compatibility allows any deviation from exact identity is between enumerated types. Meaning that int and unsigned int are not layout compatible. ---------- I'm also curious about the line in 3.9.1 para 3 which says that "the value representation of each corresponding signed/unsigned type shall be the same". I can understand what this might mean for the non-negative values of the two types, but what might it mean for the correspondence between values that are negative in the signed type and positive in the unsigned one? Thanks, Michael. --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Tom Widmer Guest Posted: Tue Apr 11, 2006 4:06 pm    Post subject: Re: layout-compatible types and value representations Michael Norrish wrote: Quote: Does the standard allow int * and unsigned * to have different value representations and alignment requirements? The language in the last sentence of 3.9.2 para 3 only requires identical representations and alignments where the types pointed at are "layout compatible". It seems that the only places were layout compatibility allows any deviation from exact identity is between enumerated types. Meaning that int and unsigned int are not layout compatible. Agreed. Quote: ---------- I'm also curious about the line in 3.9.1 para 3 which says that "the value representation of each corresponding signed/unsigned type shall be the same". I can understand what this might mean for the non-negative values of the two types, but what might it mean for the correspondence between values that are negative in the signed type and positive in the unsigned one? "The value representation of an object is the set of bits that hold the value of type T." So, the set of bits used to hold the value for the signed/unsigned types will be the same (e.g. if the least significant bit is not used by the unsigned type on some weird architecture, it shall not be used by the signed one either). Tom --- [ comp.std.c++ is moderated. To submit articles, try just posting with ] [ your news-reader. If that fails, use mailto:std-c++@ncar.ucar.edu ] [ --- Please see the FAQ before posting. --- ] [ FAQ: http://www.comeaucomputing.com/csc/faq.html ] Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language, library and standards All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.