On Saturday 26 February 2011 02:51:08 Jacob Carlborg wrote: > On 2011-02-26 02:35, Jonathan M Davis wrote: > > On Friday, February 25, 2011 17:16:31 simendsjo wrote: > >> On 26.02.2011 02:06, bearophile wrote: > >>> simendsjo: > >>>> So.. A long in C is the same as the platform size? And long long > >>>> doesn't exist in 64 bit? > >>> > >>> In D the size of int/uint is 32 bits and long/ulong is 64 bits. > >>> > >>> In C the size of int, unsigned int, long, long long int, unsigned long > >>> long int, etc are not fixed, the change according to the CPU. > >>> sizeof(int)<= sizeof(long)<= sizeof(long long). > >>> > >>> A help: > >>> http://www.digitalmars.com/d/2.0/phobos/std_stdint.html > >>> > >>> Bye, > >>> bearophile > >> > >> Ouch.. Any tips on porting C code that would work nicely with a > >> transition to 64 bit? > >> Should I change all long and int to int_atleast_32_t and long long to > >> 64? > > > > It depends entirely on what the code is doing. It could be completely > > safe to convert all ints, longs, and long longs to long to long. Or you > > may have to choose int or long depending on what system the code is > > supposed to be for. > > > > In many cases, using a larger type wouldn't matter, since it can hold > > more than the smaller type, so whether the type in C/C++ was 32 bits or > > 64 bits is irrelevant. In other cases, the type needs to be an exact > > size, because the code is doing bit shifts or whatnot (in which case > > they _should_ have been using int32_t and int64_t on Linux and whatever > > the equivalent is on Windows, but unfortunately, many programmers > > don't). And if you're dealing with a struct, it's possible that that > > struct has to be an exact size (e.g. for some binary format), and using > > the wrong type in converting could make it the wrong size. > > > > If you want to know what the appropriate D type is for the C/C++ code, > > you _need_ to know what it does. Now, IIRC, int is almost guaranteed to > > be 32 bits at this point, and long long is essentially guaranteed to be > > 64 bits, but long varies from system to system - both in terms of OS and > > architecture. IIRC, long is 32 bits on Solaris and Windows - both on x86 > > and x86_64 - but it's 32 bits in x86 Linux and 64 bits in x86_64 Linux. > > So, if all the code uses is int and long long, then it's probably > > reasonably safe to use int for int and long for long long, but it's > > ultimately system dependent. Personally, I would argue that C/C++ code > > should use int when you don't care about the size of an integral type > > and use the intX_t types (where X is 8, 16, 32, or 64) when you _do_ > > care about the size, but there's no guarantee that programmers are going > > to be that disciplined about it. > > A C "long" is 64bit long on Solaris 64bit according to this: > http://en.wikipedia.org/wiki/64-bit#Specific_C-language_data_models
Well, I've run into problems before due the size of long differing on Linux and Solaris and I thought that it was 64-bit Linux and 64-bit Solaris, but maybe it was actually 32-bit Solaris (I _know_ that it was 64-bit Linux though). Regardless, it just goes to show how careful you have to be when dealing with long in C and C++. - Jonathan M Davis
