5 files changed, 337 insertions, 0 deletions
diff --git a/ccan/compiler/LICENSE b/ccan/compiler/LICENSE
new file mode 120000
index 0000000..b7951da
--- /dev/null
+++ b/ccan/compiler/LICENSE
@@ -0,0 +1 @@
+../../licenses/CC0
+\ No newline at end of file
diff --git a/ccan/compiler/_info b/ccan/compiler/_info
new file mode 100644
index 0000000..12cb247
--- /dev/null
+++ b/ccan/compiler/_info
@@ -0,0 +1,64 @@
+#include "config.h"
+#include <string.h>
+#include <stdio.h>
+
+/**
+ * compiler - macros for common compiler extensions
+ *
+ * Abstracts away some compiler hints.  Currently these include:
+ * - COLD
+ *	For functions not called in fast paths (aka. cold functions)
+ * - PRINTF_FMT
+ *	For functions which take printf-style parameters.
+ * - CONST_FUNCTION
+ *	For functions which return the same value for same parameters.
+ * - NEEDED
+ *	For functions and variables which must be emitted even if unused.
+ * - UNNEEDED
+ *	For functions and variables which need not be emitted if unused.
+ * - UNUSED
+ *	For parameters which are not used.
+ * - IS_COMPILE_CONSTANT()
+ *	For using different tradeoffs for compiletime vs runtime evaluation.
+ *
+ * License: CC0 (Public domain)
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ *
+ * Example:
+ *	#include <ccan/compiler/compiler.h>
+ *	#include <stdio.h>
+ *	#include <stdarg.h>
+ *
+ *	// Example of a (slow-path) logging function.
+ *	static int log_threshold = 2;
+ *	static void COLD PRINTF_FMT(2,3)
+ *		logger(int level, const char *fmt, ...)
+ *	{
+ *		va_list ap;
+ *		va_start(ap, fmt);
+ *		if (level >= log_threshold)
+ *			vfprintf(stderr, fmt, ap);
+ *		va_end(ap);
+ *	}
+ *
+ *	int main(int argc, char *argv[] UNNEEDED)
+ *	{
+ *		if (argc != 1) {
+ *			logger(3, "Don't want %i arguments!\n", argc-1);
+ *			return 1;
+ *		}
+ *		return 0;
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	/* Expect exactly one argument */
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		return 0;
+	}
+
+	return 1;
+}
diff --git a/ccan/compiler/compiler.h b/ccan/compiler/compiler.h
new file mode 100644
index 0000000..bce4f25
--- /dev/null
+++ b/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 */
diff --git a/ccan/compiler/test/compile_fail-printf.c b/ccan/compiler/test/compile_fail-printf.c
new file mode 100644
index 0000000..7664f65
--- /dev/null
+++ b/ccan/compiler/test/compile_fail-printf.c
@@ -0,0 +1,24 @@
+#include <ccan/compiler/compiler.h>
+
+static void PRINTF_FMT(2,3) my_printf(int x, const char *fmt, ...)
+{
+	(void)x;
+	(void)fmt;
+}
+
+int main(void)
+{
+	unsigned int i = 0;
+
+	my_printf(1, "Not a pointer "
+#ifdef FAIL
+		  "%p",
+#if !HAVE_ATTRIBUTE_PRINTF
+#error "Unfortunately we don't fail if !HAVE_ATTRIBUTE_PRINTF."
+#endif
+#else
+		  "%i",
+#endif
+		  i);
+	return 0;
+}
diff --git a/ccan/compiler/test/run-is_compile_constant.c b/ccan/compiler/test/run-is_compile_constant.c
new file mode 100644
index 0000000..c914c68
--- /dev/null
+++ b/ccan/compiler/test/run-is_compile_constant.c
@@ -0,0 +1,17 @@
+#include <ccan/compiler/compiler.h>
+#include <ccan/tap/tap.h>
+
+int main(int argc, char *argv[])
+{
+	(void)argc;
+	(void)argv;
+	plan_tests(2);
+
+	ok1(!IS_COMPILE_CONSTANT(argc));
+#if HAVE_BUILTIN_CONSTANT_P
+	ok1(IS_COMPILE_CONSTANT(7));
+#else
+	pass("If !HAVE_BUILTIN_CONSTANT_P, IS_COMPILE_CONSTANT always false");
+#endif
+	return exit_status();
+}