--- /dev/null
+/* CC0 (Public domain) - see LICENSE file for details */
+#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 CONST_FUNCTION
+#if HAVE_ATTRIBUTE_CONST
+/**
+ * CONST_FUNCTION - 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 CONST_FUNCTION __attribute__((__const__))
+#else
+#define CONST_FUNCTION
+#endif
+
+#ifndef PURE_FUNCTION
+#if HAVE_ATTRIBUTE_PURE
+/**
+ * PURE_FUNCTION - a function is pure
+ *
+ * A pure function is one that has no side effects other than it's return value
+ * and uses no inputs other than it's arguments and global variables.
+ */
+#define PURE_FUNCTION __attribute__((__pure__))
+#else
+#define PURE_FUNCTION
+#endif
+#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 */
projects / bcachefs-tools-debian / blobdiff