8793bb7f4a
I have occasionally run into a situation where it would make sense to
control a compiler warning from a source file rather than doing so from
a Makefile using the $(cc-disable-warning, ...) or $(cc-option, ...)
helpers.
The approach here is similar to what glibc uses, using __diag() and
related macros to encapsulate a _Pragma("GCC diagnostic ...") statement
that gets turned into the respective "#pragma GCC diagnostic ..." by
the preprocessor when the macro gets expanded.
Like glibc, I also have an argument to pass the affected compiler
version, but decided to actually evaluate that one. For now, this
supports GCC_4_6, GCC_4_7, GCC_4_8, GCC_4_9, GCC_5, GCC_6, GCC_7,
GCC_8 and GCC_9. Adding support for CLANG_5 and other interesting
versions is straightforward here. GNU compilers starting with gcc-4.2
could support it in principle, but "#pragma GCC diagnostic push"
was only added in gcc-4.6, so it seems simpler to not deal with those
at all. The same versions show a large number of warnings already,
so it seems easier to just leave it at that and not do a more
fine-grained control for them.
The use cases I found so far include:
- turning off the gcc-8 -Wattribute-alias warning inside of the
SYSCALL_DEFINEx() macro without having to do it globally.
- Reducing the build time for a simple re-make after a change,
once we move the warnings from ./Makefile and
./scripts/Makefile.extrawarn into linux/compiler.h
- More control over the warnings based on other configurations,
using preprocessor syntax instead of Makefile syntax. This should make
it easier for the average developer to understand and change things.
- Adding an easy way to turn the W=1 option on unconditionally
for a subdirectory or a specific file. This has been requested
by several developers in the past that want to have their subsystems
W=1 clean.
- Integrating clang better into the build systems. Clang supports
more warnings than GCC, and we probably want to classify them
as default, W=1, W=2 etc, but there are cases in which the
warnings should be classified differently due to excessive false
positives from one or the other compiler.
- Adding a way to turn the default warnings into errors (e.g. using
a new "make E=0" tag) while not also turning the W=1 warnings into
errors.
This patch for now just adds the minimal infrastructure in order to
do the first of the list above. As the #pragma GCC diagnostic
takes precedence over command line options, the next step would be
to convert a lot of the individual Makefiles that set nonstandard
options to use __diag() instead.
[paul.burton@mips.com:
- Rebase atop current master.
- Add __diag_GCC, or more generally __diag_<compiler>, abstraction to
avoid code outside of linux/compiler-gcc.h needing to duplicate
knowledge about different GCC versions.
- Add a comment argument to __diag_{ignore,warn,error} which isn't
used in the expansion of the macros but serves to push people to
document the reason for using them - per feedback from Kees Cook.
- Translate severity to GCC-specific pragmas in linux/compiler-gcc.h
rather than using GCC-specific in linux/compiler_types.h.
- Drop all but GCC 8 macros, since we only need to define macros for
versions that we need to introduce pragmas for, and as of this
series that's just GCC 8.
- Capitalize comments in linux/compiler-gcc.h to match the style of
the rest of the file.
- Line up macro definitions with tabs in linux/compiler-gcc.h.]
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Paul Burton <paul.burton@mips.com>
Tested-by: Christophe Leroy <christophe.leroy@c-s.fr>
Tested-by: Stafford Horne <shorne@gmail.com>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
293 lines
7.4 KiB
C
293 lines
7.4 KiB
C
#ifndef __LINUX_COMPILER_TYPES_H
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#define __LINUX_COMPILER_TYPES_H
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#ifndef __ASSEMBLY__
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#ifdef __CHECKER__
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# define __user __attribute__((noderef, address_space(1)))
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# define __kernel __attribute__((address_space(0)))
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# define __safe __attribute__((safe))
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# define __force __attribute__((force))
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# define __nocast __attribute__((nocast))
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# define __iomem __attribute__((noderef, address_space(2)))
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# define __must_hold(x) __attribute__((context(x,1,1)))
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# define __acquires(x) __attribute__((context(x,0,1)))
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# define __releases(x) __attribute__((context(x,1,0)))
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# define __acquire(x) __context__(x,1)
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# define __release(x) __context__(x,-1)
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# define __cond_lock(x,c) ((c) ? ({ __acquire(x); 1; }) : 0)
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# define __percpu __attribute__((noderef, address_space(3)))
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# define __rcu __attribute__((noderef, address_space(4)))
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# define __private __attribute__((noderef))
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extern void __chk_user_ptr(const volatile void __user *);
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extern void __chk_io_ptr(const volatile void __iomem *);
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# define ACCESS_PRIVATE(p, member) (*((typeof((p)->member) __force *) &(p)->member))
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#else /* __CHECKER__ */
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# ifdef STRUCTLEAK_PLUGIN
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# define __user __attribute__((user))
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# else
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# define __user
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# endif
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# define __kernel
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# define __safe
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# define __force
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# define __nocast
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# define __iomem
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# define __chk_user_ptr(x) (void)0
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# define __chk_io_ptr(x) (void)0
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# define __builtin_warning(x, y...) (1)
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# define __must_hold(x)
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# define __acquires(x)
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# define __releases(x)
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# define __acquire(x) (void)0
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# define __release(x) (void)0
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# define __cond_lock(x,c) (c)
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# define __percpu
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# define __rcu
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# define __private
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# define ACCESS_PRIVATE(p, member) ((p)->member)
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#endif /* __CHECKER__ */
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/* Indirect macros required for expanded argument pasting, eg. __LINE__. */
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#define ___PASTE(a,b) a##b
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#define __PASTE(a,b) ___PASTE(a,b)
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#ifdef __KERNEL__
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#ifdef __GNUC__
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#include <linux/compiler-gcc.h>
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#endif
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#if defined(CC_USING_HOTPATCH) && !defined(__CHECKER__)
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#define notrace __attribute__((hotpatch(0,0)))
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#else
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#define notrace __attribute__((no_instrument_function))
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#endif
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/* Intel compiler defines __GNUC__. So we will overwrite implementations
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* coming from above header files here
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*/
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#ifdef __INTEL_COMPILER
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# include <linux/compiler-intel.h>
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#endif
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/* Clang compiler defines __GNUC__. So we will overwrite implementations
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* coming from above header files here
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*/
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#ifdef __clang__
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#include <linux/compiler-clang.h>
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#endif
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/*
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* Generic compiler-dependent macros required for kernel
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* build go below this comment. Actual compiler/compiler version
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* specific implementations come from the above header files
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*/
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struct ftrace_branch_data {
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const char *func;
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const char *file;
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unsigned line;
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union {
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struct {
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unsigned long correct;
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unsigned long incorrect;
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};
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struct {
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unsigned long miss;
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unsigned long hit;
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};
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unsigned long miss_hit[2];
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};
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};
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struct ftrace_likely_data {
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struct ftrace_branch_data data;
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unsigned long constant;
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};
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#endif /* __KERNEL__ */
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#endif /* __ASSEMBLY__ */
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#ifdef __KERNEL__
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/*
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* Allow us to mark functions as 'deprecated' and have gcc emit a nice
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* warning for each use, in hopes of speeding the functions removal.
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* Usage is:
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* int __deprecated foo(void)
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*/
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#ifndef __deprecated
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# define __deprecated /* unimplemented */
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#endif
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#ifdef MODULE
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#define __deprecated_for_modules __deprecated
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#else
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#define __deprecated_for_modules
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#endif
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#ifndef __must_check
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#define __must_check
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#endif
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#ifndef CONFIG_ENABLE_MUST_CHECK
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#undef __must_check
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#define __must_check
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#endif
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#ifndef CONFIG_ENABLE_WARN_DEPRECATED
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#undef __deprecated
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#undef __deprecated_for_modules
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#define __deprecated
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#define __deprecated_for_modules
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#endif
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#ifndef __malloc
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#define __malloc
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#endif
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/*
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* Allow us to avoid 'defined but not used' warnings on functions and data,
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* as well as force them to be emitted to the assembly file.
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*
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* As of gcc 3.4, static functions that are not marked with attribute((used))
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* may be elided from the assembly file. As of gcc 3.4, static data not so
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* marked will not be elided, but this may change in a future gcc version.
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*
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* NOTE: Because distributions shipped with a backported unit-at-a-time
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* compiler in gcc 3.3, we must define __used to be __attribute__((used))
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* for gcc >=3.3 instead of 3.4.
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*
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* In prior versions of gcc, such functions and data would be emitted, but
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* would be warned about except with attribute((unused)).
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*
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* Mark functions that are referenced only in inline assembly as __used so
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* the code is emitted even though it appears to be unreferenced.
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*/
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#ifndef __used
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# define __used /* unimplemented */
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#endif
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#ifndef __maybe_unused
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# define __maybe_unused /* unimplemented */
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#endif
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#ifndef __always_unused
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# define __always_unused /* unimplemented */
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#endif
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#ifndef noinline
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#define noinline
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#endif
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/*
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* Rather then using noinline to prevent stack consumption, use
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* noinline_for_stack instead. For documentation reasons.
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*/
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#define noinline_for_stack noinline
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#ifndef __always_inline
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#define __always_inline inline
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#endif
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#endif /* __KERNEL__ */
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/*
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* From the GCC manual:
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*
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* Many functions do not examine any values except their arguments,
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* and have no effects except the return value. Basically this is
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* just slightly more strict class than the `pure' attribute above,
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* since function is not allowed to read global memory.
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*
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* Note that a function that has pointer arguments and examines the
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* data pointed to must _not_ be declared `const'. Likewise, a
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* function that calls a non-`const' function usually must not be
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* `const'. It does not make sense for a `const' function to return
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* `void'.
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*/
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#ifndef __attribute_const__
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# define __attribute_const__ /* unimplemented */
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#endif
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#ifndef __designated_init
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# define __designated_init
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#endif
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#ifndef __latent_entropy
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# define __latent_entropy
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#endif
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#ifndef __randomize_layout
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# define __randomize_layout __designated_init
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#endif
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#ifndef __no_randomize_layout
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# define __no_randomize_layout
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#endif
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#ifndef randomized_struct_fields_start
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# define randomized_struct_fields_start
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# define randomized_struct_fields_end
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#endif
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/*
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* Tell gcc if a function is cold. The compiler will assume any path
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* directly leading to the call is unlikely.
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*/
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#ifndef __cold
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#define __cold
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#endif
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/* Simple shorthand for a section definition */
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#ifndef __section
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# define __section(S) __attribute__ ((__section__(#S)))
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#endif
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#ifndef __visible
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#define __visible
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#endif
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#ifndef __nostackprotector
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# define __nostackprotector
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#endif
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/*
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* Assume alignment of return value.
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*/
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#ifndef __assume_aligned
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#define __assume_aligned(a, ...)
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#endif
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/* Are two types/vars the same type (ignoring qualifiers)? */
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#ifndef __same_type
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# define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
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#endif
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/* Is this type a native word size -- useful for atomic operations */
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#ifndef __native_word
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# define __native_word(t) (sizeof(t) == sizeof(char) || sizeof(t) == sizeof(short) || sizeof(t) == sizeof(int) || sizeof(t) == sizeof(long))
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#endif
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#ifndef __diag
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#define __diag(string)
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#endif
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#ifndef __diag_GCC
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#define __diag_GCC(version, severity, string)
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#endif
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#define __diag_push() __diag(push)
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#define __diag_pop() __diag(pop)
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#define __diag_ignore(compiler, version, option, comment) \
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__diag_ ## compiler(version, ignore, option)
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#define __diag_warn(compiler, version, option, comment) \
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__diag_ ## compiler(version, warn, option)
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#define __diag_error(compiler, version, option, comment) \
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__diag_ ## compiler(version, error, option)
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#endif /* __LINUX_COMPILER_TYPES_H */
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