Workaround broken __builtin_clz in clang with MS codegen (#519)

fmtlib · Jun 17, 2017 · 475e40d · 475e40d
1 parent 24df4b2
commit 475e40d
Showing 1 changed file with 9 additions and 5 deletions.
diff --git a/fmt/format.h b/fmt/format.h
@@ -287,12 +287,16 @@ typedef __int64          intmax_t;
 # define FMT_ASSERT(condition, message) assert((condition) && message)
 #endif
 
-#if FMT_GCC_VERSION >= 400 || FMT_HAS_BUILTIN(__builtin_clz)
-# define FMT_BUILTIN_CLZ(n) __builtin_clz(n)
-#endif
+// __builtin_clz is broken in clang with Microsoft CodeGen:
+// https://github.com/fmtlib/fmt/issues/519
+#ifndef _MSC_VER
+# if FMT_GCC_VERSION >= 400 || FMT_HAS_BUILTIN(__builtin_clz)
+#  define FMT_BUILTIN_CLZ(n) __builtin_clz(n)
+# endif
 
-#if FMT_GCC_VERSION >= 400 || FMT_HAS_BUILTIN(__builtin_clzll)
-# define FMT_BUILTIN_CLZLL(n) __builtin_clzll(n)
+# if FMT_GCC_VERSION >= 400 || FMT_HAS_BUILTIN(__builtin_clzll)
+#  define FMT_BUILTIN_CLZLL(n) __builtin_clzll(n)
+# endif
 #endif
 
 // Some compilers masquerade as both MSVC and GCC-likes or