Mark constructing an Unexpected as cold

[folly.git] / folly / CppAttributes.h

diff --git a/folly/CppAttributes.h b/folly/CppAttributes.h
index 542e271811aa49cc9e92af51a6a80b127fedb7ab..466aab91a81144527e968415207f666674d52d46 100644 (file)
--- a/folly/CppAttributes.h
+++ b/folly/CppAttributes.h
@@ -22,6 +22,12 @@
 
 #pragma once
 
+#ifndef __has_attribute
+#define FOLLY_HAS_ATTRIBUTE(x) 0
+#else
+#define FOLLY_HAS_ATTRIBUTE(x) __has_attribute(x)
+#endif
+
 #ifndef __has_cpp_attribute
 #define FOLLY_HAS_CPP_ATTRIBUTE(x) 0
 #else
@@ -67,8 +73,8 @@
  */
 #if FOLLY_HAS_CPP_ATTRIBUTE(maybe_unused)
 #define FOLLY_MAYBE_UNUSED [[maybe_unused]]
-#elif FOLLY_HAS_CPP_ATTRIBUTE(gnu::unused)
-#define FOLLY_MAYBE_UNUSED [[gnu::unused]]
+#elif FOLLY_HAS_ATTRIBUTE(__unused__) || __GNUC__
+#define FOLLY_MAYBE_UNUSED __attribute__((__unused__))
 #else
 #define FOLLY_MAYBE_UNUSED
 #endif
@@ -92,6 +98,20 @@
  */
 #if FOLLY_HAS_EXTENSION(nullability)
 #define FOLLY_NULLABLE _Nullable
+#define FOLLY_NONNULL _Nonnull
 #else
 #define FOLLY_NULLABLE
+#define FOLLY_NONNULL
+#endif
+
+/**
+ * "Cold" indicates to the compiler that a function is only expected to be
+ * called from unlikely code paths. It can affect decisions made by the
+ * optimizer both when processing the function body and when analyzing
+ * call-sites.
+ */
+#if __GNUC__
+#define FOLLY_COLD __attribute__((__cold__))
+#else
+#define FOLLY_COLD
 #endif