[relnotes] [Fedora Project Wiki] Update of "Docs/Beats/Devel/Tools" by DavidWoodhouse

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The following page has been changed by DavidWoodhouse:
http://www.fedoraproject.org/wiki/Docs/Beats/Devel/Tools

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  = Devel Tools =
+ 
+ == Kernel header files ==
+ 
+ This release of Fedora has been built using Linux kernel headers exported directly from the kernel, using the new {{{headers_install}}} feature of the 2.6.18 kernel. Thus, the {{{glibc-kernheaders}}} package has been removed and replaced with a subpackage of the kernel; {{{kernel-headers}}}.
+ 
+ Developers may notice some changes between these new kernel headers and what was present before, including but not limited to:
+ 
+  * The {{{<linux/compiler.h>}}} header file has been removed, since it contains nothing of use to userspace.
+ 
+  * The {{{_syscallX()}}} macros are removed. Userspace should use {{{syscall()}}} from the C library instead.
+ 
+  * The {{{PAGE_SIZE}}} macro is removed from some architectures, since the page size is variable. Userspace should be using {{{sysconf(_SC_PAGE_SIZE)}}} or {{{getpagesize()}}} instead.
+ 
+  * The {{{<asm/atomic.h>}}} and {{{<asm/bitops.h>}}} header files have been removed. These were not designed for use in userspace, and would fail to compile on some architectures while silently giving non-atomic behaviour on others.
+ 
+  * Content which was previously protected with {{{#ifdef __KERNEL__}}} is now elided completely with the {{{unifdef}}} tool, so defining {{{__KERNEL___}}} in order to see parts which should not be visible to userspace is no longer effective.
+ 
+ In addition, some other header files which are not suitable for use in userspace have been removed, and still more headers have been edited to remove unsuitable content.
+ 
+ [[Admonition("note", "Kernel header changes are not Fedora-specific", "It should be noted that these changes are inherited from the upstream kernel and are not specific to Fedora. Any distribution using the current officially-exported kernel headers would be the same.")]]
+ 
  
  [[Include(/GCC)]]