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Diffstat (limited to 'contrib/ccan/compiler/compiler.h')
| -rw-r--r-- | contrib/ccan/compiler/compiler.h | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/contrib/ccan/compiler/compiler.h b/contrib/ccan/compiler/compiler.h new file mode 100644 index 0000000..bce4f25 --- /dev/null +++ b/contrib/ccan/compiler/compiler.h @@ -0,0 +1,231 @@ +/* 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 */ |