Draw a picture! char goes at 0 because it can go anywhere
short goes at 2 because it must be on a 2-byte boundary; it consumes bytes 2 and 3 char goes at 4 because this is the next byte after the short; it consumes byte 4; byte 5 is the next byte free long goes at 8 because this is the next 4-byte boundary after 5 8 + 4 = 12, so the struct takes 12 bytes On Feb 29, 12:03 pm, Karunakar Reddy <karunakar.r...@gmail.com> wrote: > how in the second case it is 12?????....can u tell the clear expl.. > > > > > > > > On Wed, Feb 29, 2012 at 8:39 AM, Gene <gene.ress...@gmail.com> wrote: > > This depends on the compiler and even on the options you give the > > compiler. The C nor C++ standards don't say. > > > So the asker of the question hasn't give you enough information. > > > If you assume 32-bit x86 gcc with no packing options or pragmas, I > > think shorts (which are 2 bytes long) are aligned on 2-byte > > boundaries. Longs and ints (both 4 bytes long) are on 4-byte > > boundaries. Chars (1 byte) can go anywhere. If you follow these > > rules, then the first will be laid out: > > > Field @ Offset > > > a @ 0 // next 3 bytes are padding to reach next 4-byte boundard > > b @ 4 > > c @ 8 // next 2 bytes are padding > > d @ 12 > > > so the struct will be 16 bytes in size (a long is 4 bytes). > > > In the second case you'll have > > > a @ 0 // next 1 byte are padding > > b @ 2 > > c @ 4 // next 3 bytes are padding > > d @ 8 > > > so the struct will be 12 bytes in size. > > > Even if you are using a 64-bit gcc (without the -m32 flag), you'll get > > an entirely different answer! > > > On Feb 29, 11:13 am, Decipher <ankurseth...@gmail.com> wrote: > > > I need some help in understanding how padding works ?? > > > Please answer the following questions with proper explanations.. > > > > struct mystruct1 > > > { > > > char a; > > > int b; > > > short c; > > > long d; > > > > }; > > > > struct mystruct2 > > > { > > > char a; > > > short b; > > > char c; > > > long d; > > > > }; > > > > What's the sizeof above 2 structures and why ?? > > > -- > > You received this message because you are subscribed to the Google Groups > > "Algorithm Geeks" group. > > To post to this group, send email to algogeeks@googlegroups.com. > > To unsubscribe from this group, send email to > > algogeeks+unsubscr...@googlegroups.com. > > For more options, visit this group at > >http://groups.google.com/group/algogeeks?hl=en. -- You received this message because you are subscribed to the Google Groups "Algorithm Geeks" group. To post to this group, send email to algogeeks@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.