thodg/cgminer/ccan/compiler/compiler.h

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• Hash : a0d14d15
  Author :
  Date : 2011-07-06T16:47:25
  

  ccan: add ccan/opt and dependencies to build.

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• ccan/compiler/compiler.h

• #ifndef CCAN_COMPILER_H
  #define CCAN_COMPILER_H
  #include "config.h"
  
  #ifndef COLD
  #if HAVE_ATTRIBUTE_COLD
  /**
   * COLD - a function is unlikely to be called.
   *
   * Used to mark an unlikely code path and optimize appropriately.
   * It is usually used on logging or error routines.
   *
   * Example:
   * static void COLD moan(const char *reason)
   * {
   *	fprintf(stderr, "Error: %s (%s)\n", reason, strerror(errno));
   * }
   */
  #define COLD __attribute__((cold))
  #else
  #define COLD
  #endif
  #endif
  
  #ifndef NORETURN
  #if HAVE_ATTRIBUTE_NORETURN
  /**
   * NORETURN - a function does not return
   *
   * Used to mark a function which exits; useful for suppressing warnings.
   *
   * Example:
   * static void NORETURN fail(const char *reason)
   * {
   *	fprintf(stderr, "Error: %s (%s)\n", reason, strerror(errno));
   *	exit(1);
   * }
   */
  #define NORETURN __attribute__((noreturn))
  #else
  #define NORETURN
  #endif
  #endif
  
  #ifndef PRINTF_FMT
  #if HAVE_ATTRIBUTE_PRINTF
  /**
   * PRINTF_FMT - a function takes printf-style arguments
   * @nfmt: the 1-based number of the function's format argument.
   * @narg: the 1-based number of the function's first variable argument.
   *
   * This allows the compiler to check your parameters as it does for printf().
   *
   * Example:
   * void PRINTF_FMT(2,3) my_printf(const char *prefix, const char *fmt, ...);
   */
  #define PRINTF_FMT(nfmt, narg) \
  	__attribute__((format(__printf__, nfmt, narg)))
  #else
  #define PRINTF_FMT(nfmt, narg)
  #endif
  #endif
  
  #ifndef IDEMPOTENT
  #if HAVE_ATTRIBUTE_CONST
  /**
   * IDEMPOTENT - a function's return depends only on its argument
   *
   * This allows the compiler to assume that the function will return the exact
   * same value for the exact same arguments.  This implies that the function
   * must not use global variables, or dereference pointer arguments.
   */
  #define IDEMPOTENT __attribute__((const))
  #else
  #define IDEMPOTENT
  #endif
  #endif
  
  #if HAVE_ATTRIBUTE_UNUSED
  #ifndef UNNEEDED
  /**
   * UNNEEDED - a variable/function may not be needed
   *
   * This suppresses warnings about unused variables or functions, but tells
   * the compiler that if it is unused it need not emit it into the source code.
   *
   * Example:
   * // With some preprocessor options, this is unnecessary.
   * static UNNEEDED int counter;
   *
   * // With some preprocessor options, this is unnecessary.
   * static UNNEEDED void add_to_counter(int add)
   * {
   *	counter += add;
   * }
   */
  #define UNNEEDED __attribute__((unused))
  #endif
  
  #ifndef NEEDED
  #if HAVE_ATTRIBUTE_USED
  /**
   * NEEDED - a variable/function is needed
   *
   * This suppresses warnings about unused variables or functions, but tells
   * the compiler that it must exist even if it (seems) unused.
   *
   * Example:
   *	// Even if this is unused, these are vital for debugging.
   *	static NEEDED int counter;
   *	static NEEDED void dump_counter(void)
   *	{
   *		printf("Counter is %i\n", counter);
   *	}
   */
  #define NEEDED __attribute__((used))
  #else
  /* Before used, unused functions and vars were always emitted. */
  #define NEEDED __attribute__((unused))
  #endif
  #endif
  
  #ifndef UNUSED
  /**
   * UNUSED - a parameter is unused
   *
   * Some compilers (eg. gcc with -W or -Wunused) warn about unused
   * function parameters.  This suppresses such warnings and indicates
   * to the reader that it's deliberate.
   *
   * Example:
   *	// This is used as a callback, so needs to have this prototype.
   *	static int some_callback(void *unused UNUSED)
   *	{
   *		return 0;
   *	}
   */
  #define UNUSED __attribute__((unused))
  #endif
  #else
  #ifndef UNNEEDED
  #define UNNEEDED
  #endif
  #ifndef NEEDED
  #define NEEDED
  #endif
  #ifndef UNUSED
  #define UNUSED
  #endif
  #endif
  
  #ifndef IS_COMPILE_CONSTANT
  #if HAVE_BUILTIN_CONSTANT_P
  /**
   * IS_COMPILE_CONSTANT - does the compiler know the value of this expression?
   * @expr: the expression to evaluate
   *
   * When an expression manipulation is complicated, it is usually better to
   * implement it in a function.  However, if the expression being manipulated is
   * known at compile time, it is better to have the compiler see the entire
   * expression so it can simply substitute the result.
   *
   * This can be done using the IS_COMPILE_CONSTANT() macro.
   *
   * Example:
   *	enum greek { ALPHA, BETA, GAMMA, DELTA, EPSILON };
   *
   *	// Out-of-line version.
   *	const char *greek_name(enum greek greek);
   *
   *	// Inline version.
   *	static inline const char *_greek_name(enum greek greek)
   *	{
   *		switch (greek) {
   *		case ALPHA: return "alpha";
   *		case BETA: return "beta";
   *		case GAMMA: return "gamma";
   *		case DELTA: return "delta";
   *		case EPSILON: return "epsilon";
   *		default: return "**INVALID**";
   *		}
   *	}
   *
   *	// Use inline if compiler knows answer.  Otherwise call function
   *	// to avoid copies of the same code everywhere.
   *	#define greek_name(g)						\
   *		 (IS_COMPILE_CONSTANT(greek) ? _greek_name(g) : greek_name(g))
   */
  #define IS_COMPILE_CONSTANT(expr) __builtin_constant_p(expr)
  #else
  /* If we don't know, assume it's not. */
  #define IS_COMPILE_CONSTANT(expr) 0
  #endif
  #endif
  
  #ifndef WARN_UNUSED_RESULT
  #if HAVE_WARN_UNUSED_RESULT
  /**
   * WARN_UNUSED_RESULT - warn if a function return value is unused.
   *
   * Used to mark a function where it is extremely unlikely that the caller
   * can ignore the result, eg realloc().
   *
   * Example:
   * // buf param may be freed by this; need return value!
   * static char *WARN_UNUSED_RESULT enlarge(char *buf, unsigned *size)
   * {
   *	return realloc(buf, (*size) *= 2);
   * }
   */
  #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
  #else
  #define WARN_UNUSED_RESULT
  #endif
  #endif
  #endif /* CCAN_COMPILER_H */
  

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