Knowing size of a data type

Hi, Without using sizeof, is there a way to get to know the size of any data type on that OS ... ??? one way I could think of is to take diff of the addresses of two variables defined consecutively. Any other way .....???? thanks, nitin

On Tue, 02 Sep 2003 15:08:24 +0530, Nitin wrote: > Hi, > > Without using sizeof, is there a way to get to know the size of any data > type on that OS ... ??? > > one way I could think of is to take diff of the addresses of two variables > defined consecutively. > Any other way .....???? Don't think they are guaranteed to be consecutive in memory, and the compiler may use padding between them anyway. regards NPV

"Nitin" <nitinma@bell-labs.com> wrote in <bj1oek$flh@netnews.proxy.lucent.com>: >Hi, > >Without using sizeof, is there a way to get to know the size of any data >type on that OS ... ??? I'm curious: may I kindly ask why you would like to stay away from using 'sizeof'? -- Air is water with holes in it.

"Nitin" <nitinma@bell-labs.com> writes: > Hi, > > Without using sizeof, is there a way to get to know the size of any data > type on that OS ... ??? > > one way I could think of is to take diff of the addresses of two variables > defined consecutively. If by "consecutive" you mean "guaranteed to be consecutive", as in an array, then yes. If `T' is a type, and `t' is a variable of type `T', then the expression `(size_t)((char *)(&t + 1) - (char *)&t)' yields the same value as `sizeof (T)'. Martin

Nils Petter Vaskinn wrote: > > On Tue, 02 Sep 2003 15:08:24 +0530, Nitin wrote: > > > Hi, > > > > Without using sizeof, is there a way to get to know the size of any data > > type on that OS ... ??? > > > > one way I could think of is to take diff of the addresses of two variables > > defined consecutively. > > Any other way .....???? > > Don't think they are guaranteed to be consecutive in memory, and the > compiler may use padding between them anyway. If they are defined as consecutive elements in an array, then they will be in consecutive memory without padding. -- pete

Martin Dickopp wrote: > "Nitin" <nitinma@bell-labs.com> writes: > > >>Hi, >> >>Without using sizeof, is there a way to get to know the size of any data >>type on that OS ... ??? >> >>one way I could think of is to take diff of the addresses of two variables >>defined consecutively. > > > If by "consecutive" you mean "guaranteed to be consecutive", as in an array, > then yes. If `T' is a type, and `t' is a variable of type `T', then the > expression `(size_t)((char *)(&t + 1) - (char *)&t)' yields the same value > as `sizeof (T)'. > But this will fail to work for datatypes. It only works for instances/objects/variables of datatypes. Take a try to write one that works for datatypes...... Bye, ../Chaitanya Atreya > Martin

On Tue, 2 Sep 2003 15:08:24 +0530, "Nitin" <nitinma@bell-labs.com> wrote in comp.lang.c: > Hi, > > Without using sizeof, is there a way to get to know the size of any data > type on that OS ... ??? > > one way I could think of is to take diff of the addresses of two variables > defined consecutively. > Any other way .....???? > > thanks, > nitin Yes, forget the nonsense and use sizeof, that's what its there for. Are you the same person who asked the same question a few months ago? Why not use sizeof? -- Jack Klein Home: http://JK-Technology.Com FAQs for comp.lang.c http://www.eskimo.com/~scs/C-faq/top.html comp.lang.c++ http://www.parashift.com/c++-faq-lite/ alt.comp.lang.learn.c-c++ ftp://snurse-l.org/pub/acllc-c++/faq

Its not a question of staying away. Just trying to find out alternate ways of doing it. "Irrwahn Grausewitz" <irrwahn@freenet.de> wrote in message news:rts8lvshqlqb0es6abl9847k07nvkt1fg5@4ax.com... > "Nitin" <nitinma@bell-labs.com> wrote in > <bj1oek$flh@netnews.proxy.lucent.com>: > >Hi, > > > >Without using sizeof, is there a way to get to know the size of any data > >type on that OS ... ??? > I'm curious: may I kindly ask why you would like to stay away from using > 'sizeof'? > > -- > Air is water with holes in it.

I got another one: ------ int a; printf("%x,%x",&a+1,&a); ------ now take diff of the two output values. This solution doesn't care whether compiler does padding between the addresses of two conseutively defined variables. BTW, does compiler do padding .... ?????? thanks, ..nitin > > On Tue, 02 Sep 2003 15:08:24 +0530, Nitin wrote: > > > > Don't think they are guaranteed to be consecutive in memory, and the > > compiler may use padding between them anyway. > > If they are defined as consecutive elements in an array, > then they will be in consecutive memory without padding. > > -- > pete

On 03 Sep 2003 14:48:36 +0200 Martin Dickopp <expires-nov2003@zero-based.org> wrote: > "Nitin" <nitinma@bell-labs.com> writes: > > > int a; > > printf("%x,%x",&a+1,&a); > > This invokes undefined behavior. The 'x' format specifier expects an > `unsigned int', but you provide a pointer. Indeed. %p is there specifically to print a pointer value in hexadecimal. -- char*x(c,k,s)char*k,*s;{if(!k)return*s-36?x(0,0,s+1):s;if(s)if(*s)c=10+(c?(x( c,k,0),x(c,k+=*s-c,s+1),*k):(x(*s,k,s+1),0));else c=10;printf(&x(~0,0,k)[c-~- c+"1"[~c<-c]],c);}main(){x(0,"^[kXc6]dn_eaoh$%c","-34*1'.+(,03#;+,)/'///*");}

Pieter Droogendijk wrote: > > On 03 Sep 2003 14:48:36 +0200 > Martin Dickopp <expires-nov2003@zero-based.org> wrote: > > "Nitin" <nitinma@bell-labs.com> writes: > > > > > int a; > > > printf("%x,%x",&a+1,&a); > > > > This invokes undefined behavior. The 'x' format specifier expects an > > `unsigned int', but you provide a pointer. > > Indeed. %p is there specifically to print a pointer value in hexadecimal. "%p" is there specifically to print a pointer value, period. Nothing is said about what the printed value should look like. Also, the pointer value to be printed must be of type `void*', not `int*' as above. -- Eric.Sosman@sun.com

Nitin wrote: > > Its not a question of staying away. Just trying to find out alternate ways > of doing it. Don't top-post, your replies belong following properly trimmed quotes. Your whole concept is dopey. Concentrate on learning the language thoroughly, don't be sidetracked with bizarre alternate ways or odd experiments. Once you have mastered the language, then you'll generally have enough information that you'll be able to answer such questions yourself. You bascially are wasting your time and ours for no good reason. Brian Rodenborn

your retentive and closed minded comments are not that helpfull. You waste your own time with pointless appends. idiot "Default User" <first.last@company.com> wrote in message news:3F5627D1.715C6C07@company.com... > Nitin wrote: > > > > Its not a question of staying away. Just trying to find out alternate ways > > of doing it. > > Don't top-post, your replies belong following properly trimmed quotes. > > Your whole concept is dopey. Concentrate on learning the language > thoroughly, don't be sidetracked with bizarre alternate ways or odd > experiments. Once you have mastered the language, then you'll generally > have enough information that you'll be able to answer such questions > yourself. > > You bascially are wasting your time and ours for no good reason. > > > > > Brian Rodenborn

Jon <jon_martin@uk.ibm.com> scribbled the following: > your retentive and closed minded comments are not that helpfull. You waste > your own time with pointless appends. idiot *PLONK* -- /-- Joona Palaste (palaste@cc.helsinki.fi) ---------------------------\ | Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++| | http://www.helsinki.fi/~palaste W++ B OP+ | \----------------------------------------- Finland rules! ------------/ "I am looking for myself. Have you seen me somewhere?" - Anon

Jon wrote: > > your retentive and closed minded comments are not that helpfull. You waste > your own time with pointless appends. idiot I'll say again, DON'T TOP-POST! Your efforts are foolish and non-instructive for a programmer who doesn't yet know the language. You are wasting time that should be devoted to that effort. Brian Rodenborn

Nitin wrote: > Hi, > > Without using sizeof, is there a way to get to know the size of any data > type on that OS ... ??? > > one way I could think of is to take diff of the addresses of two variables > defined consecutively. > Any other way .....???? > > thanks, > nitin > > There is no method to find the size of an OS's data type or structure without having a declaration or definition of that type. Operating Systems may have many types that they use. As others have said, use the "sizeof" operator. The "sizeof" operator is generally a constant that is evaluated at compile-time. The difference between the addresses of two consecutive objects is platform dependent and may be expressed in units of the type of that object. Casting to an unsigned char or placing the address into an integer may cause problems. Addresses aren't guaranteed to be convertable to an integer. Anyway, the difference computation is a run-time issue. Remember that there are more than three operating systems. Some may have displays, others not. Make no assumptions about a platform, except for what the Standard describes. -- Thomas Matthews C++ newsgroup welcome message: http://www.slack.net/~shiva/welcome.txt C++ Faq: http://www.parashift.com/c++-faq-lite C Faq: http://www.eskimo.com/~scs/c-faq/top.html alt.comp.lang.learn.c-c++ faq: http://www.raos.demon.uk/acllc-c++/faq.html Other sites: http://www.josuttis.com -- C++ STL Library book

Default User <first.last@company.com> scribbled the following: > Jon wrote: >> your retentive and closed minded comments are not that helpfull. You waste >> your own time with pointless appends. idiot > I'll say again, DON'T TOP-POST! > Your efforts are foolish and non-instructive for a programmer who > doesn't yet know the language. You are wasting time that should be > devoted to that effort. Um, Default, Jon isn't the OP here. He's not the one trying to avoid use of sizeof. -- /-- Joona Palaste (palaste@cc.helsinki.fi) ---------------------------\ | Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++| | http://www.helsinki.fi/~palaste W++ B OP+ | \----------------------------------------- Finland rules! ------------/ "To doo bee doo bee doo." - Frank Sinatra

"Nitin" <nitinma@bell-labs.com> wrote in message news:bj1oek$flh@netnews.proxy.lucent.com... > > Without using sizeof, is there a way to get to know the size > of any data type on that OS ... ??? Note that the size of a data type may not be the same for all compilers on a particular OS.