[ccan] [PATCH 2/9] compiler: Add PURE_FUNCTION

[Cody P Schafer]

CC: Rusty Russell <rusty at rustcorp.com.au>
Signed-off-by: Cody P Schafer <dev at codyps.com>
---
 ccan/compiler/compiler.h          | 14 ++++++++++++++
 tools/configurator/configurator.c |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/ccan/compiler/compiler.h b/ccan/compiler/compiler.h
index 651b47c..4224564 100644
--- a/ccan/compiler/compiler.h
+++ b/ccan/compiler/compiler.h
@@ -75,6 +75,20 @@
 #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
diff --git a/tools/configurator/configurator.c b/tools/configurator/configurator.c
index ed6acbf..5f1e2e5 100644
--- a/tools/configurator/configurator.c
+++ b/tools/configurator/configurator.c
@@ -79,6 +79,8 @@ static struct test tests[] = {
 	  "static int __attribute__((cold)) func(int x) { return x; }" },
 	{ "HAVE_ATTRIBUTE_CONST", DEFINES_FUNC, NULL, NULL,
 	  "static int __attribute__((const)) func(int x) { return x; }" },
+	{ "HAVE_ATTRIBUTE_PURE", DEFINES_FUNC, NULL, NULL,
+	  "static int __attribute__((pure)) func(int x) { return x; }" },
 	{ "HAVE_ATTRIBUTE_MAY_ALIAS", OUTSIDE_MAIN, NULL, NULL,
 	  "typedef short __attribute__((__may_alias__)) short_a;" },
 	{ "HAVE_ATTRIBUTE_NORETURN", DEFINES_FUNC, NULL, NULL,
-- 
2.0.0