C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Structure padding warnings when porting to 64 bit          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message abhivg Guest Posted: Mon May 21, 2007 9:10 am    Post subject: Structure padding warnings when porting to 64 bit Hi, I am trying to port a 32 bit Unix application to 64 bit Windows. While compiling on Windows I am getting a number of warnings related to structure padding. More specifically "warning C4820: 'seqargs' : '4' bytes padding added after data member 'stop_codon_pos'" Assuming that there is no pointer arithmetic being done on these structures, is it ok to safely ignore this warning? Abhishek Back to top Erik Wikström Guest Posted: Mon May 21, 2007 9:10 am    Post subject: Re: Structure padding warnings when porting to 64 bit On 21 Maj, 08:13, abhivg <abhi...@gmail.com> wrote: Quote: Hi, I am trying to port a 32 bit Unix application to 64 bit Windows. While compiling on Windows I am getting a number of warnings related to structure padding. More specifically "warning C4820: 'seqargs' : '4' bytes padding added after data member 'stop_codon_pos'" Assuming that there is no pointer arithmetic being done on these structures, is it ok to safely ignore this warning? This is probably better answered in a groups dedicated to your compiler/platform, see the FAQ for suggestions: http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.9 As to your question, it's hard to tell, pointer arithmetic on the structs themselves will probably be fine, since the compiler knows how large the struct is. The problems that might arise is if an offset from the address of the struct is used to access a member. Notice that this error message would not appear if there weren't some statements about the alignment of the struct or members thereof and I'll have to assume that there's some reason for that (though it does not have to be a good one). You might want to read the documentation about the warning: http://msdn2.microsoft.com/en-us/library/t7khkyth(vs.80).aspx -- Erik Wikström Back to top abhivg Guest Posted: Mon May 21, 2007 9:11 am    Post subject: Re: Structure padding warnings when porting to 64 bit On May 21, 12:18 pm, Erik Wikström <eri...@student.chalmers.se> wrote: Quote: On 21 Maj, 08:13, abhivg <abhi...@gmail.com> wrote: Hi, I am trying to port a 32 bit Unix application to 64 bit Windows. While compiling on Windows I am getting a number of warnings related to structure padding. More specifically "warning C4820: 'seqargs' : '4' bytes padding added after data member 'stop_codon_pos'" Assuming that there is no pointer arithmetic being done on these structures, is it ok to safely ignore this warning? This is probably better answered in a groups dedicated to your compiler/platform, see the FAQ for suggestions:http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.9 As to your question, it's hard to tell, pointer arithmetic on the structs themselves will probably be fine, since the compiler knows how large the struct is. The problems that might arise is if an offset from the address of the struct is used to access a member. Notice that this error message would not appear if there weren't some statements about the alignment of the struct or members thereof and I'll have to assume that there's some reason for that (though it does not have to be a good one). You might want to read the documentation about the warning:http://msdn2.microsoft.com/en-us/library/t7khkyth(vs.80).aspx -- Erik Wikström Thanks for replying Erik, By pointer arithmetic, I meant addition of pointers with offsets (magic numbers). So besides use of pointers and hardcoded offsets, is there any area where padding might be a problem? Quote: From what I understood, structure padding is done by the compiler mainly to speed up memory access. Sorry about posting my question in the wrong group. Will remember that from now on. regards, Abhishek 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 (comp.lang.c++) 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.