Hi, On 10/12/2016 11:51 PM, Thomas Weber wrote: > I am maintaining lcms2. In #749975, I received a patch to ensure correct > alignment for doubles von MIPS. I have forwarded the patch upstream[1], but > in the latest release, upstream has chosen a different way. It is now > possible to configure the alignment via a preprocessor variable > CMS_PTR_ALIGNMENT[2]: > // Alignment to memory pointer > > // (Ultra)SPARC with gcc requires ptr alignment of 8 bytes > // even though sizeof(void *) is only four: for greatest flexibility > // allow the build to specify ptr alignment. > #ifndef CMS_PTR_ALIGNMENT > # define CMS_PTR_ALIGNMENT sizeof(void *) > #endif > > #define _cmsALIGNMEM(x) (((x)+(CMS_PTR_ALIGNMENT - 1)) & ~(CMS_PTR_ALIGNMENT > - 1)) > > I would like to drop the Debian-specific patch. But what value for > CMS_PTR_ALIGNMENT would be good/sufficient on all arches?
Use _Alignof(type), that will always be correct. :-) For example: #define POINTER_ALIGNMENT _Alignof(void *) #define DOUBLE_ALIGNMENT _Alignof(double) Technically, this was introduced in C11/C++11, so if you need to support really old compilers, this may be problematic, but gcc/clang have supported that for a while. (A quick test tells me that gcc and clang from Jessie already support it.) Regards, Christian
