Add a dmnsn_unreachable() macro.

Also rename inline.h to compiler.h.

2 files changed, 24 insertions, 7 deletions

diff --git a/libdimension/dimension/inline.h b/libdimension/dimension/compiler.h
index e17c60e..5ce8ce8 100644
--- a/libdimension/dimension/inline.h
+++ b/libdimension/dimension/compiler.h
@@ -20,10 +20,7 @@
 
 /**
  * @file
- * Inline function support. Handle inlines nicely without cheating and making
- * them static.  The DMNSN_INLINE macro is set appropriately for the version of
- * C you're using, and non-inline versions are emitted in exactly one
- * translation unit when necessary.
+ * Compiler abstractions.
  */
 
 /**
@@ -47,3 +44,9 @@
     #define DMNSN_INLINE static
   #endif
 #endif
+
+#ifdef __GNUC__
+  #define DMNSN_UNREACHABLE() __builtin_unreachable();
+#else
+  #define DMNSN_UNREACHABLE()
+#endif
diff --git a/libdimension/dimension/error.h b/libdimension/dimension/error.h
index ae8ba01..894899a 100644
--- a/libdimension/dimension/error.h
+++ b/libdimension/dimension/error.h
@@ -39,8 +39,11 @@
  * Report an error.
  * @param[in] str       A string to print explaining the error.
  */
-#define dmnsn_error(str)                                        \
-  dmnsn_report_error(true, DMNSN_FUNC, __FILE__, __LINE__, str)
+#define dmnsn_error(str)                                                \
+  do {                                                                  \
+    dmnsn_report_error(true, DMNSN_FUNC, __FILE__, __LINE__, str);      \
+    DMNSN_UNREACHABLE();                                                \
+  } while (0)
 
 /**
  * @def dmnsn_assert
@@ -54,12 +57,23 @@
   #define dmnsn_assert(expr, str)                 \
     do {                                          \
       if (!(expr)) {                              \
-        dmnsn_error((str));  \
+        dmnsn_error((str));                       \
       }                                           \
     } while (0)
 #endif
 
 /**
+ * @def dmnsn_unreachable
+ * Express that a line of code is unreachable.
+ * @param[in] str  A string to print if the line is reached.
+ */
+#ifdef NDEBUG
+  #define dmnsn_unreachable(str) DMNSN_UNREACHABLE()
+#else
+  #define dmnsn_unreachable(str) dmnsn_error((str))
+#endif
+
+/**
  * @internal
  * Called by dmnsn_warning() and dmnsn_error(); don't call directly.
  * @param[in] die   Whether the error is fatal.