mirror of
git://jb55.com/damus
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dbe1260b54
We'll need this for our lightning invoice view Signed-off-by: William Casarin <jb55@jb55.com>
318 lines
8.0 KiB
C
318 lines
8.0 KiB
C
/* CC0 (Public domain) - see LICENSE file for details */
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#ifndef CCAN_COMPILER_H
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#define CCAN_COMPILER_H
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#include "config.h"
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#ifndef COLD
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#if HAVE_ATTRIBUTE_COLD
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/**
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* COLD - a function is unlikely to be called.
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*
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* Used to mark an unlikely code path and optimize appropriately.
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* It is usually used on logging or error routines.
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*
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* Example:
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* static void COLD moan(const char *reason)
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* {
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* fprintf(stderr, "Error: %s (%s)\n", reason, strerror(errno));
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* }
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*/
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#define COLD __attribute__((__cold__))
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#else
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#define COLD
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#endif
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#endif
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#ifndef NORETURN
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#if HAVE_ATTRIBUTE_NORETURN
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/**
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* NORETURN - a function does not return
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*
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* Used to mark a function which exits; useful for suppressing warnings.
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*
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* Example:
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* static void NORETURN fail(const char *reason)
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* {
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* fprintf(stderr, "Error: %s (%s)\n", reason, strerror(errno));
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* exit(1);
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* }
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*/
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#define NORETURN __attribute__((__noreturn__))
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#else
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#define NORETURN
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#endif
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#endif
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#ifndef PRINTF_FMT
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#if HAVE_ATTRIBUTE_PRINTF
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/**
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* PRINTF_FMT - a function takes printf-style arguments
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* @nfmt: the 1-based number of the function's format argument.
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* @narg: the 1-based number of the function's first variable argument.
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*
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* This allows the compiler to check your parameters as it does for printf().
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*
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* Example:
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* void PRINTF_FMT(2,3) my_printf(const char *prefix, const char *fmt, ...);
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*/
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#define PRINTF_FMT(nfmt, narg) \
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__attribute__((format(__printf__, nfmt, narg)))
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#else
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#define PRINTF_FMT(nfmt, narg)
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#endif
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#endif
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#ifndef CONST_FUNCTION
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#if HAVE_ATTRIBUTE_CONST
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/**
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* CONST_FUNCTION - a function's return depends only on its argument
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*
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* This allows the compiler to assume that the function will return the exact
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* same value for the exact same arguments. This implies that the function
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* must not use global variables, or dereference pointer arguments.
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*/
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#define CONST_FUNCTION __attribute__((__const__))
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#else
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#define CONST_FUNCTION
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#endif
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#ifndef PURE_FUNCTION
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#if HAVE_ATTRIBUTE_PURE
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/**
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* PURE_FUNCTION - a function is pure
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*
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* A pure function is one that has no side effects other than it's return value
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* and uses no inputs other than it's arguments and global variables.
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*/
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#define PURE_FUNCTION __attribute__((__pure__))
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#else
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#define PURE_FUNCTION
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#endif
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#endif
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#endif
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#if HAVE_ATTRIBUTE_UNUSED
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#ifndef UNNEEDED
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/**
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* UNNEEDED - a variable/function may not be needed
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*
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* This suppresses warnings about unused variables or functions, but tells
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* the compiler that if it is unused it need not emit it into the source code.
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*
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* Example:
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* // With some preprocessor options, this is unnecessary.
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* static UNNEEDED int counter;
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*
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* // With some preprocessor options, this is unnecessary.
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* static UNNEEDED void add_to_counter(int add)
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* {
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* counter += add;
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* }
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*/
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#define UNNEEDED __attribute__((__unused__))
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#endif
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#ifndef NEEDED
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#if HAVE_ATTRIBUTE_USED
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/**
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* NEEDED - a variable/function is needed
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*
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* This suppresses warnings about unused variables or functions, but tells
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* the compiler that it must exist even if it (seems) unused.
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*
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* Example:
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* // Even if this is unused, these are vital for debugging.
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* static NEEDED int counter;
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* static NEEDED void dump_counter(void)
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* {
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* printf("Counter is %i\n", counter);
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* }
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*/
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#define NEEDED __attribute__((__used__))
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#else
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/* Before used, unused functions and vars were always emitted. */
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#define NEEDED __attribute__((__unused__))
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#endif
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#endif
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#ifndef UNUSED
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/**
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* UNUSED - a parameter is unused
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*
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* Some compilers (eg. gcc with -W or -Wunused) warn about unused
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* function parameters. This suppresses such warnings and indicates
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* to the reader that it's deliberate.
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*
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* Example:
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* // This is used as a callback, so needs to have this prototype.
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* static int some_callback(void *unused UNUSED)
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* {
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* return 0;
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* }
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*/
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#define UNUSED __attribute__((__unused__))
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#endif
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#else
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#ifndef UNNEEDED
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#define UNNEEDED
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#endif
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#ifndef NEEDED
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#define NEEDED
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#endif
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#ifndef UNUSED
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#define UNUSED
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#endif
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#endif
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#ifndef IS_COMPILE_CONSTANT
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#if HAVE_BUILTIN_CONSTANT_P
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/**
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* IS_COMPILE_CONSTANT - does the compiler know the value of this expression?
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* @expr: the expression to evaluate
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*
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* When an expression manipulation is complicated, it is usually better to
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* implement it in a function. However, if the expression being manipulated is
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* known at compile time, it is better to have the compiler see the entire
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* expression so it can simply substitute the result.
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*
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* This can be done using the IS_COMPILE_CONSTANT() macro.
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*
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* Example:
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* enum greek { ALPHA, BETA, GAMMA, DELTA, EPSILON };
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*
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* // Out-of-line version.
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* const char *greek_name(enum greek greek);
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*
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* // Inline version.
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* static inline const char *_greek_name(enum greek greek)
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* {
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* switch (greek) {
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* case ALPHA: return "alpha";
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* case BETA: return "beta";
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* case GAMMA: return "gamma";
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* case DELTA: return "delta";
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* case EPSILON: return "epsilon";
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* default: return "**INVALID**";
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* }
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* }
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*
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* // Use inline if compiler knows answer. Otherwise call function
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* // to avoid copies of the same code everywhere.
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* #define greek_name(g) \
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* (IS_COMPILE_CONSTANT(greek) ? _greek_name(g) : greek_name(g))
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*/
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#define IS_COMPILE_CONSTANT(expr) __builtin_constant_p(expr)
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#else
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/* If we don't know, assume it's not. */
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#define IS_COMPILE_CONSTANT(expr) 0
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#endif
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#endif
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#ifndef WARN_UNUSED_RESULT
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#if HAVE_WARN_UNUSED_RESULT
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/**
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* WARN_UNUSED_RESULT - warn if a function return value is unused.
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*
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* Used to mark a function where it is extremely unlikely that the caller
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* can ignore the result, eg realloc().
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*
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* Example:
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* // buf param may be freed by this; need return value!
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* static char *WARN_UNUSED_RESULT enlarge(char *buf, unsigned *size)
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* {
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* return realloc(buf, (*size) *= 2);
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* }
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*/
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#define WARN_UNUSED_RESULT __attribute__((__warn_unused_result__))
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#else
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#define WARN_UNUSED_RESULT
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#endif
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#endif
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#if HAVE_ATTRIBUTE_DEPRECATED
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/**
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* WARN_DEPRECATED - warn that a function/type/variable is deprecated when used.
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*
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* Used to mark a function, type or variable should not be used.
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*
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* Example:
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* WARN_DEPRECATED char *oldfunc(char *buf);
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*/
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#define WARN_DEPRECATED __attribute__((__deprecated__))
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#else
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#define WARN_DEPRECATED
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#endif
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#if HAVE_ATTRIBUTE_NONNULL
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/**
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* NO_NULL_ARGS - specify that no arguments to this function can be NULL.
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*
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* The compiler will warn if any pointer args are NULL.
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*
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* Example:
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* NO_NULL_ARGS char *my_copy(char *buf);
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*/
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#define NO_NULL_ARGS __attribute__((__nonnull__))
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/**
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* NON_NULL_ARGS - specify that some arguments to this function can't be NULL.
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* @...: 1-based argument numbers for which args can't be NULL.
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*
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* The compiler will warn if any of the specified pointer args are NULL.
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*
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* Example:
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* char *my_copy2(char *buf, char *maybenull) NON_NULL_ARGS(1);
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*/
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#define NON_NULL_ARGS(...) __attribute__((__nonnull__(__VA_ARGS__)))
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#else
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#define NO_NULL_ARGS
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#define NON_NULL_ARGS(...)
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#endif
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#if HAVE_ATTRIBUTE_RETURNS_NONNULL
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/**
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* RETURNS_NONNULL - specify that this function cannot return NULL.
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*
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* Mainly an optimization opportunity, but can also suppress warnings.
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*
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* Example:
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* RETURNS_NONNULL char *my_copy(char *buf);
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*/
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#define RETURNS_NONNULL __attribute__((__returns_nonnull__))
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#else
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#define RETURNS_NONNULL
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#endif
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#if HAVE_ATTRIBUTE_SENTINEL
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/**
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* LAST_ARG_NULL - specify the last argument of a variadic function must be NULL.
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*
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* The compiler will warn if the last argument isn't NULL.
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*
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* Example:
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* char *join_string(char *buf, ...) LAST_ARG_NULL;
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*/
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#define LAST_ARG_NULL __attribute__((__sentinel__))
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#else
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#define LAST_ARG_NULL
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#endif
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#if HAVE_BUILTIN_CPU_SUPPORTS
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/**
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* cpu_supports - test if current CPU supports the named feature.
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*
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* This takes a literal string, and currently only works on glibc platforms.
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*
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* Example:
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* if (cpu_supports("mmx"))
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* printf("MMX support engaged!\n");
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*/
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#define cpu_supports(x) __builtin_cpu_supports(x)
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#else
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#define cpu_supports(x) 0
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#endif /* HAVE_BUILTIN_CPU_SUPPORTS */
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#endif /* CCAN_COMPILER_H */
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