commit eebaa9bfc593d5a46b293c1abd929fbfbfd28199
author Serhiy Storchaka <storchaka@gmail.com> Mon Mar 09 20:49:52 2020 +0200
committer GitHub <noreply@github.com> Mon Mar 09 20:49:52 2020 +0200
tree 9ba0bbaba8116eb71d0b80f11b586fe063aadbe5
parent 6d0ee60740f2862a878f009671b1aaa75aeb0c2a

bpo-38249: Expand Py_UNREACHABLE() to __builtin_unreachable() in the release mode. (GH-16329)

Co-authored-by: Victor Stinner <vstinner@python.org>

Include/pymacro.h

diff --git a/Include/pymacro.h b/Include/pymacro.h
index c080fb1..856cae7 100644
--- a/Include/pymacro.h
+++ b/Include/pymacro.h
@@ -101,7 +101,7 @@
 #endif
 
 #if defined(RANDALL_WAS_HERE)
-#define Py_UNREACHABLE() \
+#  define Py_UNREACHABLE() \
     Py_FatalError( \
         "If you're seeing this, the code is in what I thought was\n" \
         "an unreachable state.\n\n" \
@@ -113,13 +113,17 @@
         "I'm so sorry.\n" \
         "https://xkcd.com/2200")
 #elif defined(Py_DEBUG)
-#define Py_UNREACHABLE() \
+#  define Py_UNREACHABLE() \
     Py_FatalError( \
         "We've reached an unreachable state. Anything is possible.\n" \
         "The limits were in our heads all along. Follow your dreams.\n" \
         "https://xkcd.com/2200")
+#elif defined(__GNUC__) || defined(__clang__) || defined(__INTEL_COMPILER)
+#  define Py_UNREACHABLE() __builtin_unreachable()
+#elif defined(_MSC_VER)
+#  define Py_UNREACHABLE() __assume(0)
 #else
-#define Py_UNREACHABLE() \
+#  define Py_UNREACHABLE() \
     Py_FatalError("Unreachable C code path reached")
 #endif