"Artem B. Bityuckiy" <abityuckiy@xxxxxxxxx> writes: > Hello guys. I have already asked this > (http://gcc.gnu.org/ml/gcc-help/2004-03/msg00350.html). May be this > time I'll be lucky and get more answers... > > I'm writing some code that depends on sizeof(wchar_t). If > sizeof(wchar_t) > 2 I'm doing one things, if sizeof(wchar_t) = 2 - > another things. I need to determine sizeof(wchar_t) in > precompiler. How can I do this? > > My logic is: sizeof(wchar_t) is given by gcc. I can use > --with-target-short-wchar gcc's configure script option and gcc will > generate 2-byte wchar_t variables. Therefore, there must be some > predefined GCC's macro using which I can determine the size of > wchar_t. Right? > > The code for which I need to know sizeof(wchar_t) is written for > Newlib (small standard C library). As I understand situation with > wchar_t is similar to situation with other basic C types - they are > defined with help of gcc's stddef.h or limits.h. > > llewelly advised me to use WCHAR_MAX macro. > > I tried to use something like this: > > #if WCHAR_MAX > 0xFFFF > blablabla > #else > blablabla > #endif > > But to my surprise I've found out that I have WCHAR_MAX==0x7FFFFFFFu > when sizeof(wchar_t)==2! I've seen into wchar.h of Newlib - there is > something like > > #ifndef _WCHAR_MAX > #define WCHAR_MAX 0x7FFFFFFFu > #else > #define WCHAR_MAX _WCHAR_MAX > #else This sounds like a newlib bug to me. You should report it. > > This is similar to defines of other limits macros. I've seen to GCC's > headers and not found any _WCHAR_MAX reference there. > > I have seen to other libc's (FreeBSD's and Glibc) - they also rely on > _WCHAR_MAX, but _WCHAR_MAX isn't from GCC, but is from target-depended > files (also placed in that libc) as I've understood. > > Therefore I can conclude that sizeof(wchar_t) is considered as > target-dependent. An I can't vary gcc (using or not > --with-target-short-wchar option when compiling it)... > > But I want to have one target that is built differently depending on > sizeof(wchar_t) that is defined by GCC. How can I do this? > > One obvious way is to use construction like > > if (sizeof(wchar_t) > 2) > { > blablabala > } > else > { > blablabla > } > > but I want to rely on precompiler, not on compiler. The normal solution is to make configure compile run a program which outputs sizeof(wchar_t), and then substitutes that value into your header files. I didn't suggest this before because somehow I had the impression you were using a cross-compiler (which means the configure-time program which determines sizeof(wchar_t) must be downloaded to your target and its output somehow uploaded back, something which is not always feasible.)
