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@@ -575,12 +575,6 @@ struct sysinfo {
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char _f[20-2*sizeof(long)-sizeof(int)]; /* Padding: libc5 uses this.. */
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};
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-/* Force a compilation error if condition is true */
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-#define BUILD_BUG_ON(condition) ((void)BUILD_BUG_ON_ZERO(condition))
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-
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-/* Force a compilation error if condition is constant and true */
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-#define MAYBE_BUILD_BUG_ON(cond) ((void)sizeof(char[1 - 2 * !!(cond)]))
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-
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/* Force a compilation error if a constant expression is not a power of 2 */
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#define BUILD_BUG_ON_NOT_POWER_OF_2(n) \
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BUILD_BUG_ON((n) == 0 || (((n) & ((n) - 1)) != 0))
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@@ -592,6 +586,32 @@ struct sysinfo {
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#define BUILD_BUG_ON_ZERO(e) (sizeof(struct { int:-!!(e); }))
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#define BUILD_BUG_ON_NULL(e) ((void *)sizeof(struct { int:-!!(e); }))
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+/**
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+ * BUILD_BUG_ON - break compile if a condition is true.
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+ * @cond: the condition which the compiler should know is false.
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+ *
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+ * If you have some code which relies on certain constants being equal, or
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+ * other compile-time-evaluated condition, you should use BUILD_BUG_ON to
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+ * detect if someone changes it.
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+ *
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+ * The implementation uses gcc's reluctance to create a negative array, but
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+ * gcc (as of 4.4) only emits that error for obvious cases (eg. not arguments
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+ * to inline functions). So as a fallback we use the optimizer; if it can't
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+ * prove the condition is false, it will cause a link error on the undefined
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+ * "__build_bug_on_failed". This error message can be harder to track down
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+ * though, hence the two different methods.
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+ */
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+#ifndef __OPTIMIZE__
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+#define BUILD_BUG_ON(condition) ((void)sizeof(char[1 - 2*!!(condition)]))
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+#else
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+extern int __build_bug_on_failed;
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+#define BUILD_BUG_ON(condition) \
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+ do { \
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+ ((void)sizeof(char[1 - 2*!!(condition)])); \
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+ if (condition) __build_bug_on_failed = 1; \
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+ } while(0)
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+#endif
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+
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/* Trap pasters of __FUNCTION__ at compile-time */
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#define __FUNCTION__ (__func__)
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