5 files changed, 76 insertions, 0 deletions
diff --git a/src/lib/cc/.may_include b/src/lib/cc/.may_include
index 2b06e8519c..fa1478ce46 100644
--- a/src/lib/cc/.may_include
+++ b/src/lib/cc/.may_include
@@ -1 +1,2 @@
 orconfig.h
+lib/cc/*.h
+\ No newline at end of file
diff --git a/src/lib/cc/compat_compiler.h b/src/lib/cc/compat_compiler.h
index 3a0f307186..18b76cc1a1 100644
--- a/src/lib/cc/compat_compiler.h
+++ b/src/lib/cc/compat_compiler.h
@@ -217,4 +217,16 @@
 /** Macro: Yields the number of elements in array x. */
 #define ARRAY_LENGTH(x) ((sizeof(x)) / sizeof(x[0]))
 
+/**
+ * "Eat" a semicolon that somebody puts at the end of a top-level macro.
+ *
+ * Frequently, we want to declare a macro that people will use at file scope,
+ * and we want to allow people to put a semicolon after the macro.
+ *
+ * This declaration of a struct can be repeated any number of times, and takes
+ * a trailing semicolon afterwards.
+ **/
+#define EAT_SEMICOLON                                   \
+  struct dummy_semicolon_eater__
+
 #endif /* !defined(TOR_COMPAT_H) */
diff --git a/src/lib/cc/ctassert.h b/src/lib/cc/ctassert.h
new file mode 100644
index 0000000000..e42976360f
--- /dev/null
+++ b/src/lib/cc/ctassert.h
@@ -0,0 +1,53 @@
+/* Copyright (c) 2018 The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file ctassert.h
+ *
+ * \brief Compile-time assertions: CTASSERT(expression).
+ */
+
+#ifndef TOR_CTASSERT_H
+#define TOR_CTASSERT_H
+
+#include "lib/cc/compat_compiler.h"
+
+/**
+ * CTASSERT(expression)
+ *
+ *       Trigger a compiler error if expression is false.
+ */
+#if __STDC_VERSION__ >= 201112L
+
+/* If C11 is available, just use _Static_assert.  */
+#define CTASSERT(x) _Static_assert((x), #x)
+
+#else
+
+/*
+ * If C11 is not available, expand __COUNTER__, or __INCLUDE_LEVEL__
+ * and __LINE__, or just __LINE__, with an intermediate preprocessor
+ * macro CTASSERT_EXPN, and then use CTASSERT_DECL to paste the
+ * expansions together into a unique name.
+ *
+ * We use this name as a typedef of an array type with a positive
+ * length if the assertion is true, and a negative length of the
+ * assertion is false, which is invalid and hence triggers a compiler
+ * error.
+ */
+#if defined(__COUNTER__)
+#define CTASSERT(x) CTASSERT_EXPN((x), c, __COUNTER__)
+#elif defined(__INCLUDE_LEVEL__)
+#define CTASSERT(x) CTASSERT_EXPN((x), __INCLUDE_LEVEL__, __LINE__)
+#else
+/* hope it's unique enough */
+#define CTASSERT(x) CTASSERT_EXPN((x), l, __LINE__)
+#endif
+
+#define CTASSERT_EXPN(x, a, b) CTASSERT_DECL(x, a, b)
+#define CTASSERT_DECL(x, a, b) \
+  typedef char tor_ctassert_##a##_##b[(x) ? 1 : -1] ATTR_UNUSED
+
+#endif
+
+#endif /* !defined(TOR_CTASSERT_H) */
diff --git a/src/lib/cc/include.am b/src/lib/cc/include.am
index 2ae90f97dd..52cf8a9f72 100644
--- a/src/lib/cc/include.am
+++ b/src/lib/cc/include.am
@@ -1,4 +1,5 @@
 
 noinst_HEADERS += \
 	src/lib/cc/compat_compiler.h \
+	src/lib/cc/ctassert.h \
 	src/lib/cc/torint.h
diff --git a/src/lib/cc/torint.h b/src/lib/cc/torint.h
index c9b2d329f2..9a66aada18 100644
--- a/src/lib/cc/torint.h
+++ b/src/lib/cc/torint.h
@@ -125,4 +125,13 @@ typedef int32_t ssize_t;
 /** Any size_t larger than this amount is likely to be an underflow. */
 #define SIZE_T_CEILING  ((size_t)(SSIZE_MAX-16))
 
+#if SIZEOF_INT > SIZEOF_VOID_P
+#error "sizeof(int) > sizeof(void *) - Tor cannot be built on this platform!"
+#endif
+
+#if SIZEOF_UNSIGNED_INT > SIZEOF_VOID_P
+#error "sizeof(unsigned int) > sizeof(void *) - Tor cannot be built on this \
+platform!"
+#endif
+
 #endif /* !defined(TOR_TORINT_H) */