diff --git a/src/builtin_proto.h b/src/builtin_proto.h
index b68d6fb3379f9..35b6bfbbe499f 100644
--- a/src/builtin_proto.h
+++ b/src/builtin_proto.h
@@ -1,5 +1,5 @@
-#ifndef _BUILTIN_PROTO_H_
-#define _BUILTIN_PROTO_H_
+#ifndef BUILTIN_PROTO_H
+#define BUILTIN_PROTO_H
 
 // declarations for julia-callable builtin functions
 
diff --git a/src/flisp/equalhash.h b/src/flisp/equalhash.h
index a6f086dd6eaa2..03a5a3ceec95b 100644
--- a/src/flisp/equalhash.h
+++ b/src/flisp/equalhash.h
@@ -1,5 +1,5 @@
-#ifndef __EQUALHASH_H_
-#define __EQUALHASH_H_
+#ifndef EQUALHASH_H
+#define EQUALHASH_H
 
 #include "htableh.inc"
 
diff --git a/src/flisp/flisp.h b/src/flisp/flisp.h
index e36669de67f9c..a892b435c1b36 100644
--- a/src/flisp/flisp.h
+++ b/src/flisp/flisp.h
@@ -1,5 +1,5 @@
-#ifndef _FLISP_H_
-#define _FLISP_H_
+#ifndef FLISP_H
+#define FLISP_H
 
 #include "libsupport.h"
 
diff --git a/src/flisp/opcodes.h b/src/flisp/opcodes.h
index bdccc15f43847..593270c8b31d3 100644
--- a/src/flisp/opcodes.h
+++ b/src/flisp/opcodes.h
@@ -1,5 +1,5 @@
-#ifndef __OPCODES_H_
-#define __OPCODES_H_
+#ifndef OPCODES_H
+#define OPCODES_H
 
 enum {
     OP_NOP=0, OP_DUP, OP_POP, OP_CALL, OP_TCALL, OP_JMP, OP_BRF, OP_BRT,
diff --git a/src/jltypes_internal.h b/src/jltypes_internal.h
index e10e304b96890..8a8ce21399c96 100644
--- a/src/jltypes_internal.h
+++ b/src/jltypes_internal.h
@@ -1,5 +1,5 @@
-#ifndef _JLTYPES_INTERNAL_H_
-#define _JLTYPES_INTERNAL_H_
+#ifndef JLTYPES_INTERNAL_H
+#define JLTYPES_INTERNAL_H
 
 void jl_cache_type_(jl_tag_type_t *type);
 
diff --git a/src/julia.h b/src/julia.h
index f7e5e9cb509c8..86a230c7e6815 100644
--- a/src/julia.h
+++ b/src/julia.h
@@ -1,5 +1,5 @@
-#ifndef _JULIA_H_
-#define _JULIA_H_
+#ifndef JULIA_H
+#define JULIA_H
 
 #include "libsupport.h"
 
diff --git a/src/newobj_internal.h b/src/newobj_internal.h
index 39c8a4ca4ea09..53ed4c9aa2ecf 100644
--- a/src/newobj_internal.h
+++ b/src/newobj_internal.h
@@ -1,5 +1,5 @@
-#ifndef _NEWOBJ_INTERNAL_H_
-#define _NEWOBJ_INTERNAL_H_
+#ifndef NEWOBJ_INTERNAL_H
+#define NEWOBJ_INTERNAL_H
 
 static inline jl_value_t *newobj(jl_type_t *type, size_t nfields)
 {
diff --git a/src/support/MurmurHash3.h b/src/support/MurmurHash3.h
index 58e98204d289c..67521ef9556fa 100644
--- a/src/support/MurmurHash3.h
+++ b/src/support/MurmurHash3.h
@@ -2,8 +2,8 @@
 // MurmurHash3 was written by Austin Appleby, and is placed in the public
 // domain. The author hereby disclaims copyright to this source code.
 
-#ifndef _MURMURHASH3_H_
-#define _MURMURHASH3_H_
+#ifndef MURMURHASH3_H
+#define MURMURHASH3_H
 
 //-----------------------------------------------------------------------------
 // Platform-specific functions and macros
@@ -34,4 +34,4 @@ void MurmurHash3_x64_128 ( const void * key, int len, uint32_t seed, void * out
 
 //-----------------------------------------------------------------------------
 
-#endif // _MURMURHASH3_H_
+#endif // MURMURHASH3_H
diff --git a/src/support/arraylist.h b/src/support/arraylist.h
index b8f427077325f..6605f02a5b43d 100644
--- a/src/support/arraylist.h
+++ b/src/support/arraylist.h
@@ -1,5 +1,5 @@
-#ifndef __ARRAYLIST_H_
-#define __ARRAYLIST_H_
+#ifndef ARRAYLIST_H
+#define ARRAYLIST_H
 
 #define AL_N_INLINE 29
 
diff --git a/src/support/bitvector.h b/src/support/bitvector.h
index 3e9b77d16a7ff..54d718959423a 100644
--- a/src/support/bitvector.h
+++ b/src/support/bitvector.h
@@ -1,5 +1,5 @@
-#ifndef __BITVECTOR_H_
-#define __BITVECTOR_H_
+#ifndef BITVECTOR_H
+#define BITVECTOR_H
 
 // a mask with n set lo or hi bits
 #define lomask(n) (u_int32_t)((((u_int32_t)1)<<(n))-1)
diff --git a/src/support/dirpath.h b/src/support/dirpath.h
index 01a40cfc10809..24d236947cf20 100644
--- a/src/support/dirpath.h
+++ b/src/support/dirpath.h
@@ -1,5 +1,5 @@
-#ifndef __DIRPATH_H_
-#define __DIRPATH_H_
+#ifndef DIRPATH_H
+#define DIRPATH_H
 
 #ifdef WIN32
 #define PATHSEP '\\'
diff --git a/src/support/dtypes.h b/src/support/dtypes.h
index 27af451729ccb..400c42ed6f5a7 100644
--- a/src/support/dtypes.h
+++ b/src/support/dtypes.h
@@ -1,5 +1,5 @@
-#ifndef __DTYPES_H_
-#define __DTYPES_H_
+#ifndef DTYPES_H
+#define DTYPES_H
 
 /*
   This file defines sane integer types for our target platforms. This
diff --git a/src/support/hashing.h b/src/support/hashing.h
index f267f9dcbf519..0c28abfa7e60e 100644
--- a/src/support/hashing.h
+++ b/src/support/hashing.h
@@ -1,5 +1,5 @@
-#ifndef __HASHING_H_
-#define __HASHING_H_
+#ifndef HASHING_H
+#define HASHING_H
 
 uint_t nextipow2(uint_t i);
 DLLEXPORT u_int32_t int32hash(u_int32_t a);
diff --git a/src/support/htable.h b/src/support/htable.h
index 3c1e5c9a3f96b..ca6905a6d1324 100644
--- a/src/support/htable.h
+++ b/src/support/htable.h
@@ -1,5 +1,5 @@
-#ifndef __HTABLE_H_
-#define __HTABLE_H_
+#ifndef HTABLE_H
+#define HTABLE_H
 
 #define HT_N_INLINE 32
 
diff --git a/src/support/ieee754.h b/src/support/ieee754.h
index c900e32da334a..443c67e94fb98 100644
--- a/src/support/ieee754.h
+++ b/src/support/ieee754.h
@@ -1,5 +1,5 @@
-#ifndef __IEEE754_H_
-#define __IEEE754_H_
+#ifndef IEEE754_H
+#define IEEE754_H
 
 #ifdef __linux
 
@@ -70,6 +70,6 @@ union ieee854_long_double {
 
 #define IEEE854_LONG_DOUBLE_BIAS 0x3fff
 
-#endif // ifdef __APPLE__ ...
+#endif
 
 #endif
diff --git a/src/support/ios.h b/src/support/ios.h
index 14cfe96a298f7..f21a11d27f1ce 100644
--- a/src/support/ios.h
+++ b/src/support/ios.h
@@ -1,5 +1,5 @@
-#ifndef __IOS_H_
-#define __IOS_H_
+#ifndef IOS_H
+#define IOS_H
 
 #include <stdarg.h>
 #include <pthread.h>
diff --git a/src/support/libsupport.h b/src/support/libsupport.h
index fc51e46b79d64..28f7f531ed2d4 100644
--- a/src/support/libsupport.h
+++ b/src/support/libsupport.h
@@ -1,5 +1,5 @@
-#ifndef __LIBSUPPORT_H_
-#define __LIBSUPPORT_H_
+#ifndef LIBSUPPORT_H
+#define LIBSUPPORT_H
 
 #include <stdarg.h>
 #include "dtypes.h"
diff --git a/src/support/ptrhash.h b/src/support/ptrhash.h
index 824545920bd09..e35615cdaf161 100644
--- a/src/support/ptrhash.h
+++ b/src/support/ptrhash.h
@@ -1,5 +1,5 @@
-#ifndef __PTRHASH_H_
-#define __PTRHASH_H_
+#ifndef PTRHASH_H
+#define PTRHASH_H
 
 #include "htableh.inc"
 
diff --git a/src/support/socket.h b/src/support/socket.h
index f2385e272c5cd..b170b798b2e65 100644
--- a/src/support/socket.h
+++ b/src/support/socket.h
@@ -1,5 +1,5 @@
-#ifndef __LLTSOCKET_H_
-#define __LLTSOCKET_H_
+#ifndef LLTSOCKET_H
+#define LLTSOCKET_H
 
 #ifdef WIN32
 #include <winsock2.h>
diff --git a/src/support/timefuncs.h b/src/support/timefuncs.h
index 81ca6146db344..1d98fac35dc60 100644
--- a/src/support/timefuncs.h
+++ b/src/support/timefuncs.h
@@ -1,5 +1,5 @@
-#ifndef __TIMEFUNCS_H_
-#define __TIMEFUNCS_H_
+#ifndef TIMEFUNCS_H
+#define TIMEFUNCS_H
 
 u_int64_t i64time(void);
 DLLEXPORT double clock_now(void);
diff --git a/src/support/utf8.h b/src/support/utf8.h
index 509ab6ca607a7..15329f9072245 100644
--- a/src/support/utf8.h
+++ b/src/support/utf8.h
@@ -1,5 +1,5 @@
-#ifndef __UTF8_H_
-#define __UTF8_H_
+#ifndef UTF8_H
+#define UTF8_H
 
 extern int locale_is_utf8;
 
diff --git a/src/support/utils.h b/src/support/utils.h
index 289dea9e6aa40..857789e46358e 100644
--- a/src/support/utils.h
+++ b/src/support/utils.h
@@ -1,5 +1,5 @@
-#ifndef __UTILS_H_
-#define __UTILS_H_
+#ifndef UTILS_H
+#define UTILS_H
 
 DLLEXPORT int double_exponent(double d);
 void snprint_real(char *s, size_t cnt, double r,