On 21 May 2013 18:22, Joseph S. Myers <jos...@codesourcery.com> wrote: > On Tue, 21 May 2013, Ard Biesheuvel wrote: > >> I am currently exploring various ways of using NEON instructions in >> kernel mode. One of the ways of doing so is using NEON intrinsics, >> which we would like to support in the kernel, but unfortunately, at >> the moment we can't because the support header arm_neon.h assumes C99 >> conformance and includes <stdint.h>. The kernel does not supply that >> header. > > GCC, however, does, and for Linux targets it installs stdint-wrap.h which > for freestanding builds includes stdint-gcc.h rather than depending on the > C library to provide the header. So as long as the kernel build uses > -ffreestanding, it should not matter that the kernel doesn't have its own > stdint.h. >
I am aware of that. However, depending on whether your GCC was built to target bare metal or glibc, the definition for uintptr_t that you get as a bonus from including stdint-gcc.h (a type which arm_neon.h itself does not require) conflicts with the one that the kernel defines. (bare metal and the kernel both use unsigned long, whereas glibc uses unsigned int) As it is quite customary to use a glibc targeted GCC to build the kernel, I would like to avoid being the one to introduce the restriction that only bare metal compilers can build the kernel. (Note that the kernel does not define -ffreestanding by default, although it mostly compiles fine with it) -- Ard.
