cpp: Use #pragma once instead of #ifndef guards

This both says what we mean and silences a bunch of spurious CPP linting
warnings. This pragma is supported by all CPP implementations which we
support.

Reviewers: austin, erikd, simonmar, hvr

Reviewed By: simonmar

Subscribers: rwbarton, thomie

Differential Revision: https://phabricator.haskell.org/D3482

59 files changed, 60 insertions, 241 deletions

diff --git a/includes/Cmm.h b/includes/Cmm.h
index 276348a6c9..779416b6da 100644
--- a/includes/Cmm.h
+++ b/includes/Cmm.h
@@ -25,8 +25,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef CMM_H
-#define CMM_H
+#pragma once
 
 /*
  * In files that are included into both C and C-- (and perhaps
@@ -942,5 +941,3 @@
     }                                                          \
                                                                \
     return (dst);
-
-#endif /* CMM_H */
diff --git a/includes/HsFFI.h b/includes/HsFFI.h
index 53478a7a5e..bee942c44c 100644
--- a/includes/HsFFI.h
+++ b/includes/HsFFI.h
@@ -9,8 +9,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef HSFFI_H
-#define HSFFI_H
+#pragma once
 
 #ifdef __cplusplus
 extern "C" {
@@ -122,5 +121,3 @@ extern void hs_try_putmvar (int capability, HsStablePtr sp);
 #ifdef __cplusplus
 }
 #endif
-
-#endif /* HSFFI_H */
diff --git a/includes/MachDeps.h b/includes/MachDeps.h
index 380b3fb061..778975ea3c 100644
--- a/includes/MachDeps.h
+++ b/includes/MachDeps.h
@@ -13,8 +13,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef MACHDEPS_H
-#define MACHDEPS_H
+#pragma once
 
 /* Don't allow stage1 (cross-)compiler embed assumptions about target
  * platform. When ghc-stage1 is being built by ghc-stage0 is should not
@@ -122,5 +121,3 @@
 #define TAG_MASK ((1 << TAG_BITS) - 1)
 
 #endif /* !defined(STAGE) || STAGE >= 2 */
-
-#endif /* MACHDEPS_H */
diff --git a/includes/Rts.h b/includes/Rts.h
index be49b326f2..b36fc94a5e 100644
--- a/includes/Rts.h
+++ b/includes/Rts.h
@@ -10,8 +10,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_H
-#define RTS_H
+#pragma once
 
 #ifdef __cplusplus
 extern "C" {
@@ -313,5 +312,3 @@ TICK_VAR(2)
 #ifdef __cplusplus
 }
 #endif
-
-#endif /* RTS_H */
diff --git a/includes/RtsAPI.h b/includes/RtsAPI.h
index e5326f759b..f9b561800d 100644
--- a/includes/RtsAPI.h
+++ b/includes/RtsAPI.h
@@ -9,8 +9,7 @@
  *
  * --------------------------------------------------------------------------*/
 
-#ifndef RTSAPI_H
-#define RTSAPI_H
+#pragma once
 
 #ifdef __cplusplus
 extern "C" {
@@ -445,5 +444,3 @@ extern StgWord base_GHCziTopHandler_runNonIO_closure[];
 #ifdef __cplusplus
 }
 #endif
-
-#endif /* RTSAPI_H */
diff --git a/includes/Stg.h b/includes/Stg.h
index 619984d8e5..ff5e3174c0 100644
--- a/includes/Stg.h
+++ b/includes/Stg.h
@@ -23,8 +23,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef STG_H
-#define STG_H
+#pragma once
 
 #if !(__STDC_VERSION__ >= 199901L)
 # error __STDC_VERSION__ does not advertise C99 or later
@@ -567,5 +566,3 @@ typedef union {
   c;                                            \
 })
 #endif
-
-#endif /* STG_H */
diff --git a/includes/ghcconfig.h b/includes/ghcconfig.h
index 5f10e923fd..7b99835a23 100644
--- a/includes/ghcconfig.h
+++ b/includes/ghcconfig.h
@@ -1,7 +1,4 @@
-#ifndef __GHCCONFIG_H__
-#define __GHCCONFIG_H__
+#pragma once
 
 #include "ghcautoconf.h"
 #include "ghcplatform.h"
-
-#endif
diff --git a/includes/rts/Adjustor.h b/includes/rts/Adjustor.h
index 5e96a072fb..49fd62652d 100644
--- a/includes/rts/Adjustor.h
+++ b/includes/rts/Adjustor.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_ADJUSTOR_H
-#define RTS_ADJUSTOR_H
+#pragma once
 
 /* Creating and destroying an adjustor thunk */
 void* createAdjustor (int cconv, 
@@ -21,5 +20,3 @@ void* createAdjustor (int cconv,
                       char *typeString);
 
 void freeHaskellFunctionPtr (void* ptr);
-
-#endif /* RTS_ADJUSTOR_H */
diff --git a/includes/rts/BlockSignals.h b/includes/rts/BlockSignals.h
index 166d7bb3fe..23bc9859e0 100644
--- a/includes/rts/BlockSignals.h
+++ b/includes/rts/BlockSignals.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_BLOCKSIGNALS_H
-#define RTS_BLOCKSIGNALS_H
+#pragma once
 
 /* Used by runProcess() in the process package
  */
@@ -33,5 +32,3 @@ void blockUserSignals(void);
  * The inverse of blockUserSignals(); re-enable the deliver of console events.
  */
 void unblockUserSignals(void);
-
-#endif /* RTS_BLOCKSIGNALS_H */
diff --git a/includes/rts/Config.h b/includes/rts/Config.h
index 51ee74fdb8..43057773f2 100644
--- a/includes/rts/Config.h
+++ b/includes/rts/Config.h
@@ -13,8 +13,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_CONFIG_H
-#define RTS_CONFIG_H
+#pragma once
 
 #if defined(TICKY_TICKY) && defined(THREADED_RTS)
 #error TICKY_TICKY is incompatible with THREADED_RTS
@@ -47,5 +46,3 @@
 /* Profile spin locks */
 
 #define PROF_SPIN
-
-#endif /* RTS_CONFIG_H */
diff --git a/includes/rts/Constants.h b/includes/rts/Constants.h
index 62fa833173..27097bf45b 100644
--- a/includes/rts/Constants.h
+++ b/includes/rts/Constants.h
@@ -17,8 +17,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_CONSTANTS_H
-#define RTS_CONSTANTS_H
+#pragma once
 
 /* -----------------------------------------------------------------------------
    Minimum closure sizes
@@ -314,5 +313,3 @@
  * we can have static arrays of this size in the RTS for speed.
  */
 #define MAX_NUMA_NODES 16
-
-#endif /* RTS_CONSTANTS_H */
diff --git a/includes/rts/EventLogFormat.h b/includes/rts/EventLogFormat.h
index d6838abd8a..160aa19303 100644
--- a/includes/rts/EventLogFormat.h
+++ b/includes/rts/EventLogFormat.h
@@ -73,8 +73,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_EVENTLOGFORMAT_H
-#define RTS_EVENTLOGFORMAT_H
+#pragma once
 
 /*
  * Markers for begin/end of the Header.
@@ -245,5 +244,3 @@ typedef StgWord64 EventTaskId;         /* for EVENT_TASK_* */
 typedef StgWord64 EventKernelThreadId; /* for EVENT_TASK_CREATE */
 
 #endif
-
-#endif /* RTS_EVENTLOGFORMAT_H */
diff --git a/includes/rts/EventLogWriter.h b/includes/rts/EventLogWriter.h
index f9cb25fe62..829b0f2697 100644
--- a/includes/rts/EventLogWriter.h
+++ b/includes/rts/EventLogWriter.h
@@ -6,8 +6,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef EVENTLOG_WRITER_H
-#define EVENTLOG_WRITER_H
+#pragma once
 
 #include <stddef.h>
 #include <stdbool.h>
@@ -36,5 +35,3 @@ typedef struct {
  * a file `program.eventlog`.
  */
 extern const EventLogWriter FileEventLogWriter;
-
-#endif /* EVENTLOG_WRITER_H */
diff --git a/includes/rts/FileLock.h b/includes/rts/FileLock.h
index e4c7c66fa7..8bc08141cf 100644
--- a/includes/rts/FileLock.h
+++ b/includes/rts/FileLock.h
@@ -11,12 +11,9 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_FILELOCK_H
-#define RTS_FILELOCK_H
+#pragma once
 
 #include "Stg.h"
 
 int  lockFile(int fd, StgWord64 dev, StgWord64 ino, int for_writing);
 int  unlockFile(int fd);
-
-#endif /* RTS_FILELOCK_H */
diff --git a/includes/rts/Flags.h b/includes/rts/Flags.h
index 5195a3a627..405fce166d 100644
--- a/includes/rts/Flags.h
+++ b/includes/rts/Flags.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_FLAGS_H
-#define RTS_FLAGS_H
+#pragma once
 
 #include <stdio.h>
 #include <stdint.h>
@@ -282,5 +281,3 @@ extern char  **prog_argv;
 */
 extern int      rts_argc;  /* ditto */
 extern char   **rts_argv;
-
-#endif	/* RTS_FLAGS_H */
diff --git a/includes/rts/GetTime.h b/includes/rts/GetTime.h
index e5dbd9e238..5b75b01bb8 100644
--- a/includes/rts/GetTime.h
+++ b/includes/rts/GetTime.h
@@ -11,9 +11,6 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_GETTIME_H
-#define RTS_GETTIME_H
+#pragma once
 
 StgWord64 getMonotonicNSec (void);
-
-#endif /* RTS_GETTIME_H */
diff --git a/includes/rts/Globals.h b/includes/rts/Globals.h
index e3ff643556..63d26e7814 100644
--- a/includes/rts/Globals.h
+++ b/includes/rts/Globals.h
@@ -14,8 +14,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_GLOBALS_H
-#define RTS_GLOBALS_H
+#pragma once
 
 #define mkStoreAccessorPrototype(name)                                  \
     StgStablePtr                                                        \
@@ -35,5 +34,3 @@ mkStoreAccessorPrototype(LibHSghcInitLinkerDone)
 mkStoreAccessorPrototype(LibHSghcGlobalDynFlags)
 mkStoreAccessorPrototype(LibHSghcStaticOptions)
 mkStoreAccessorPrototype(LibHSghcStaticOptionsReady)
-
-#endif /* RTS_GLOBALS_H */
diff --git a/includes/rts/Hpc.h b/includes/rts/Hpc.h
index d70d1db829..58d4813ac1 100644
--- a/includes/rts/Hpc.h
+++ b/includes/rts/Hpc.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_HPC_H
-#define RTS_HPC_H
+#pragma once
 
 // Simple linked list of modules
 typedef struct _HpcModuleInfo {
@@ -33,5 +32,3 @@ HpcModuleInfo * hs_hpc_rootModule (void);
 
 void startupHpc(void);
 void exitHpc(void);
-
-#endif /* RTS_HPC_H */
diff --git a/includes/rts/IOManager.h b/includes/rts/IOManager.h
index f9e2cd7958..5d79a64b00 100644
--- a/includes/rts/IOManager.h
+++ b/includes/rts/IOManager.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_IOMANAGER_H
-#define RTS_IOMANAGER_H
+#pragma once
 
 #if defined(mingw32_HOST_OS)
 
@@ -42,5 +41,3 @@ void ioManagerWakeup (void);
 void ioManagerDie (void);
 void ioManagerStart (void);
 #endif
-
-#endif /* RTS_IOMANAGER_H */
diff --git a/includes/rts/Libdw.h b/includes/rts/Libdw.h
index 6a3b95e462..391847552e 100644
--- a/includes/rts/Libdw.h
+++ b/includes/rts/Libdw.h
@@ -6,10 +6,7 @@
  *
  * --------------------------------------------------------------------------*/
 
-#include "Rts.h"
-
-#ifndef RTS_LIBDW_H
-#define RTS_LIBDW_H
+#pragma once
 
 // Chunk capacity
 // This is rather arbitrary
@@ -92,5 +89,3 @@ Backtrace *libdwGetBacktrace(LibdwSession *session);
 /* Lookup Location information for the given address.
  * Returns 0 if successful, 1 if address could not be found. */
 int libdwLookupLocation(LibdwSession *session, Location *loc, StgPtr pc);
-
-#endif /* RTS_LIBDW_H */
diff --git a/includes/rts/LibdwPool.h b/includes/rts/LibdwPool.h
index 3360192725..76ff41c8c7 100644
--- a/includes/rts/LibdwPool.h
+++ b/includes/rts/LibdwPool.h
@@ -6,8 +6,7 @@
  *
  * --------------------------------------------------------------------------*/
 
-#ifndef RTS_LIBDW_POOL_H
-#define RTS_LIBDW_POOL_H
+#pragma once
 
 /* Claim a session from the pool */
 LibdwSession *libdwPoolTake(void);
@@ -18,5 +17,3 @@ void libdwPoolRelease(LibdwSession *sess);
 /* Free any sessions in the pool forcing a reload of any loaded debug
  * information */
 void libdwPoolClear(void);
-
-#endif /* RTS_LIBDW_POOL_H */
diff --git a/includes/rts/Linker.h b/includes/rts/Linker.h
index 34bf0df741..793195b3ab 100644
--- a/includes/rts/Linker.h
+++ b/includes/rts/Linker.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_LINKER_H
-#define RTS_LINKER_H
+#pragma once
 
 #if defined(mingw32_HOST_OS)
 typedef wchar_t pathchar;
@@ -86,5 +85,3 @@ pathchar* findSystemLibrary(pathchar* dll_name);
 
 /* called by the initialization code for a module, not a user API */
 StgStablePtr foreignExportStablePtr (StgPtr p);
-
-#endif /* RTS_LINKER_H */
diff --git a/includes/rts/Main.h b/includes/rts/Main.h
index 1c332fc95c..05924ad92b 100644
--- a/includes/rts/Main.h
+++ b/includes/rts/Main.h
@@ -6,8 +6,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTSMAIN_H
-#define RTSMAIN_H
+#pragma once
 
 /* -----------------------------------------------------------------------------
  * The entry point for Haskell programs that use a Haskell main function
@@ -17,5 +16,3 @@ int hs_main (int argc, char *argv[],     // program args
              StgClosure *main_closure,   // closure for Main.main
              RtsConfig rts_config)       // RTS configuration
    GNUC3_ATTRIBUTE(__noreturn__);
-
-#endif /* RTSMAIN_H */
diff --git a/includes/rts/Messages.h b/includes/rts/Messages.h
index 85ffddaffd..2a6a84b821 100644
--- a/includes/rts/Messages.h
+++ b/includes/rts/Messages.h
@@ -14,8 +14,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_MESSAGES_H
-#define RTS_MESSAGES_H
+#pragma once
 
 #include <stdarg.h>
 
@@ -102,5 +101,3 @@ extern RtsMsgFunction rtsFatalInternalErrorFn;
 extern RtsMsgFunction rtsDebugMsgFn;
 extern RtsMsgFunction rtsErrorMsgFn;
 extern RtsMsgFunction rtsSysErrorMsgFn;
-
-#endif /* RTS_MESSAGES_H */
diff --git a/includes/rts/OSThreads.h b/includes/rts/OSThreads.h
index 2ebbd1e0f1..05e52d919a 100644
--- a/includes/rts/OSThreads.h
+++ b/includes/rts/OSThreads.h
@@ -12,8 +12,7 @@
  *
  * --------------------------------------------------------------------------*/
 
-#ifndef RTS_OSTHREADS_H
-#define RTS_OSTHREADS_H
+#pragma once
 
 #if defined(HAVE_PTHREAD_H) && !defined(mingw32_HOST_OS)
 
@@ -257,5 +256,3 @@ typedef StgWord64 KernelThreadId;
 KernelThreadId kernelThreadId (void);
 
 #endif /* CMINUSMINUS */
-
-#endif /* RTS_OSTHREADS_H */
diff --git a/includes/rts/Parallel.h b/includes/rts/Parallel.h
index 2c84327729..de1c6e1fae 100644
--- a/includes/rts/Parallel.h
+++ b/includes/rts/Parallel.h
@@ -11,9 +11,6 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_PARALLEL_H
-#define RTS_PARALLEL_H
+#pragma once
 
 StgInt newSpark (StgRegTable *reg, StgClosure *p);
-
-#endif /* RTS_PARALLEL_H */
diff --git a/includes/rts/PrimFloat.h b/includes/rts/PrimFloat.h
index 248ea6246f..835a18aac4 100644
--- a/includes/rts/PrimFloat.h
+++ b/includes/rts/PrimFloat.h
@@ -9,12 +9,9 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_PRIMFLOAT_H
-#define RTS_PRIMFLOAT_H
+#pragma once
 
 StgDouble __int_encodeDouble (I_ j, I_ e);
 StgFloat  __int_encodeFloat (I_ j, I_ e);
 StgDouble __word_encodeDouble (W_ j, I_ e);
 StgFloat  __word_encodeFloat (W_ j, I_ e);
-
-#endif /* RTS_PRIMFLOAT_H */
diff --git a/includes/rts/Signals.h b/includes/rts/Signals.h
index 22cbe4ad77..d321b0d0c4 100644
--- a/includes/rts/Signals.h
+++ b/includes/rts/Signals.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_SIGNALS_H
-#define RTS_SIGNALS_H
+#pragma once
 
 /* NB. #included in Haskell code, no prototypes in here. */
 
@@ -22,5 +21,3 @@
 #define STG_SIG_ERR   (-3)
 #define STG_SIG_HAN   (-4)
 #define STG_SIG_RST   (-5)
-
-#endif /* RTS_SIGNALS_H */
diff --git a/includes/rts/SpinLock.h b/includes/rts/SpinLock.h
index dccd86705c..6530a3a2f0 100644
--- a/includes/rts/SpinLock.h
+++ b/includes/rts/SpinLock.h
@@ -19,9 +19,8 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_SPINLOCK_H
-#define RTS_SPINLOCK_H
- 
+#pragma once
+
 #if defined(THREADED_RTS)
 
 #if defined(PROF_SPIN)
@@ -112,6 +111,3 @@ INLINE_HEADER void initSpinLock(void * p STG_UNUSED)
 { /* nothing */ }
 
 #endif /* THREADED_RTS */
-
-#endif /* RTS_SPINLOCK_H */
-
diff --git a/includes/rts/Stable.h b/includes/rts/Stable.h
index f75b9ab806..75fcf4f7eb 100644
--- a/includes/rts/Stable.h
+++ b/includes/rts/Stable.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_STABLE_H
-#define RTS_STABLE_H
+#pragma once
 
 EXTERN_INLINE StgPtr deRefStablePtr (StgStablePtr stable_ptr);
 StgStablePtr getStablePtr  (StgPtr p);
@@ -39,5 +38,3 @@ StgPtr deRefStablePtr(StgStablePtr sp)
 {
     return stable_ptr_table[(StgWord)sp].addr;
 }
-
-#endif /* RTS_STABLE_H */
diff --git a/includes/rts/StaticPtrTable.h b/includes/rts/StaticPtrTable.h
index e536f4b496..97a1720823 100644
--- a/includes/rts/StaticPtrTable.h
+++ b/includes/rts/StaticPtrTable.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_STATICPTRTABLE_H
-#define RTS_STATICPTRTABLE_H
+#pragma once
 
 /** Inserts an entry in the Static Pointer Table.
  *
@@ -43,5 +42,3 @@ void hs_spt_insert_stableptr(StgWord64 key[2], StgStablePtr *entry);
  *
  * */
 void hs_spt_remove (StgWord64 key[2]);
-
-#endif /* RTS_STATICPTRTABLE_H */
diff --git a/includes/rts/TTY.h b/includes/rts/TTY.h
index f0b4225fbf..3555818c4a 100644
--- a/includes/rts/TTY.h
+++ b/includes/rts/TTY.h
@@ -11,10 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_TTY_H
-#define RTS_TTY_H
+#pragma once
 
 void* __hscore_get_saved_termios(int fd);
 void  __hscore_set_saved_termios(int fd, void* ts);
-
-#endif /* RTS_TTY_H */
diff --git a/includes/rts/Threads.h b/includes/rts/Threads.h
index f45d351c2b..17a64c1ba0 100644
--- a/includes/rts/Threads.h
+++ b/includes/rts/Threads.h
@@ -12,8 +12,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_THREADS_H
-#define RTS_THREADS_H
+#pragma once
 
 #ifdef HAVE_SYS_TYPES_H
 #include <sys/types.h>
@@ -75,5 +74,3 @@ extern Capability MainCapability;
 // current value at the moment).
 //
 extern void setNumCapabilities (uint32_t new_);
-
-#endif /* RTS_THREADS_H */
diff --git a/includes/rts/Ticky.h b/includes/rts/Ticky.h
index ff4d44a0d0..de4e518430 100644
--- a/includes/rts/Ticky.h
+++ b/includes/rts/Ticky.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_TICKY_H
-#define RTS_TICKY_H
+#pragma once
 
 /* -----------------------------------------------------------------------------
    The StgEntCounter type - needed regardless of TICKY_TICKY
@@ -31,5 +30,3 @@ typedef struct _StgEntCounter {
     StgInt      allocs;         /* number of allocations by this fun */
     struct _StgEntCounter *link;/* link to chain them all together */
 } StgEntCounter;
-
-#endif /* RTS_TICKY_H */
diff --git a/includes/rts/Time.h b/includes/rts/Time.h
index a1debedea0..5fa166e125 100644
--- a/includes/rts/Time.h
+++ b/includes/rts/Time.h
@@ -9,8 +9,7 @@
  *
  * --------------------------------------------------------------------------*/
 
-#ifndef RTSTIME_H
-#define RTSTIME_H
+#pragma once
 
 // For most time values in the RTS we use a fixed resolution of nanoseconds,
 // normalising the time we get from platform-dependent APIs to this
@@ -39,5 +38,3 @@ INLINE_HEADER Time fsecondsToTime (double t)
 {
     return (Time)(t * TIME_RESOLUTION);
 }
-
-#endif // RTSTIME_H
diff --git a/includes/rts/Timer.h b/includes/rts/Timer.h
index ca039537d3..f0a63d8d39 100644
--- a/includes/rts/Timer.h
+++ b/includes/rts/Timer.h
@@ -11,11 +11,8 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_TIMER_H
-#define RTS_TIMER_H
+#pragma once
 
 void startTimer (void);
 void stopTimer  (void);
 int rtsTimerSignal (void);
-
-#endif /* RTS_TIMER_H */
diff --git a/includes/rts/Types.h b/includes/rts/Types.h
index 4b0e680ae5..242b831819 100644
--- a/includes/rts/Types.h
+++ b/includes/rts/Types.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_TYPES_H
-#define RTS_TYPES_H
+#pragma once
 
 #include <stddef.h>
 #include <stdbool.h>
@@ -30,5 +29,3 @@ typedef unsigned int nat __attribute__((deprecated));  /* uint32_t */
 typedef struct StgClosure_   StgClosure;
 typedef struct StgInfoTable_ StgInfoTable;
 typedef struct StgTSO_       StgTSO;
-
-#endif /* RTS_TYPES_H */
diff --git a/includes/rts/Utils.h b/includes/rts/Utils.h
index a4a57ab332..4ab025b887 100644
--- a/includes/rts/Utils.h
+++ b/includes/rts/Utils.h
@@ -10,10 +10,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_UTILS_H
-#define RTS_UTILS_H
+#pragma once
 
 /* Alternate to raise(3) for threaded rts, for BSD-based OSes */
 int genericRaise(int sig);
-
-#endif /* RTS_UTILS_H */
diff --git a/includes/rts/prof/CCS.h b/includes/rts/prof/CCS.h
index 1ed53c1d7c..4805063a0f 100644
--- a/includes/rts/prof/CCS.h
+++ b/includes/rts/prof/CCS.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_PROF_CCS_H
-#define RTS_PROF_CCS_H
+#pragma once
 
 /* -----------------------------------------------------------------------------
  * Data Structures
@@ -253,5 +252,3 @@ extern CostCentreStack * RTS_VAR(CCS_LIST);         // registered CCS list
 #define ENTER_CCS_THUNK(cap,p) doNothing()
 
 #endif /* PROFILING */
-
-#endif /* RTS_PROF_CCS_H */
diff --git a/includes/rts/prof/LDV.h b/includes/rts/prof/LDV.h
index 7d6f9ff409..fdbab4d901 100644
--- a/includes/rts/prof/LDV.h
+++ b/includes/rts/prof/LDV.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_PROF_LDV_H
-#define RTS_PROF_LDV_H
+#pragma once
 
 #ifdef PROFILING
 
@@ -43,5 +42,3 @@
 #define LDV_RECORD_CREATE(c)   /* nothing */
 
 #endif /* PROFILING */
-
-#endif /* STGLDVPROF_H */
diff --git a/includes/rts/storage/Block.h b/includes/rts/storage/Block.h
index 7d6f102ab8..3c6f2b1fba 100644
--- a/includes/rts/storage/Block.h
+++ b/includes/rts/storage/Block.h
@@ -6,8 +6,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_STORAGE_BLOCK_H
-#define RTS_STORAGE_BLOCK_H
+#pragma once
 
 #include "ghcconfig.h"
 
@@ -351,4 +350,3 @@ round_up_to_mblocks(StgWord words)
 }
 
 #endif /* !CMINUSMINUS */
-#endif /* RTS_STORAGE_BLOCK_H */
diff --git a/includes/rts/storage/ClosureMacros.h b/includes/rts/storage/ClosureMacros.h
index c8c270fdfe..af77df37b5 100644
--- a/includes/rts/storage/ClosureMacros.h
+++ b/includes/rts/storage/ClosureMacros.h
@@ -6,8 +6,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_STORAGE_CLOSUREMACROS_H
-#define RTS_STORAGE_CLOSUREMACROS_H
+#pragma once
 
 /* -----------------------------------------------------------------------------
    Info tables are slammed up against the entry code, and the label
@@ -596,5 +595,3 @@ EXTERN_INLINE void overwritingClosureOfs (StgClosure *p, uint32_t offset)
     for (i = offset; i < size; i++)
         ((StgWord *)p)[i] = 0;
 }
-
-#endif /* RTS_STORAGE_CLOSUREMACROS_H */
diff --git a/includes/rts/storage/ClosureTypes.h b/includes/rts/storage/ClosureTypes.h
index 234e00b174..68cc919257 100644
--- a/includes/rts/storage/ClosureTypes.h
+++ b/includes/rts/storage/ClosureTypes.h
@@ -7,8 +7,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_STORAGE_CLOSURETYPES_H
-#define RTS_STORAGE_CLOSURETYPES_H
+#pragma once
 
 /* 
  * WARNING WARNING WARNING
@@ -83,5 +82,3 @@
 #define SMALL_MUT_ARR_PTRS_FROZEN     62
 #define COMPACT_NFDATA                63
 #define N_CLOSURE_TYPES               64
-
-#endif /* RTS_STORAGE_CLOSURETYPES_H */
diff --git a/includes/rts/storage/Closures.h b/includes/rts/storage/Closures.h
index 2c62552b2f..f5baead002 100644
--- a/includes/rts/storage/Closures.h
+++ b/includes/rts/storage/Closures.h
@@ -6,8 +6,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_STORAGE_CLOSURES_H
-#define RTS_STORAGE_CLOSURES_H
+#pragma once
 
 /*
  * The Layout of a closure header depends on which kind of system we're
@@ -475,6 +474,3 @@ typedef struct StgCompactNFData_ {
       // Used temporarily to store the result of compaction.  Doesn't need to be
       // a GC root.
 } StgCompactNFData;
-
-
-#endif /* RTS_STORAGE_CLOSURES_H */
diff --git a/includes/rts/storage/FunTypes.h b/includes/rts/storage/FunTypes.h
index 8c565888c1..27858fb82b 100644
--- a/includes/rts/storage/FunTypes.h
+++ b/includes/rts/storage/FunTypes.h
@@ -6,8 +6,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_STORAGE_FUNTYPES_H
-#define RTS_STORAGE_FUNTYPES_H
+#pragma once
 
 /* generic - function comes with a small bitmap */
 #define ARG_GEN      0   
@@ -53,5 +52,3 @@
 #define ARG_PPPPPP   26
 #define ARG_PPPPPPP  27
 #define ARG_PPPPPPPP 28
-
-#endif /* RTS_STORAGE_FUNTYPES_H */
diff --git a/includes/rts/storage/GC.h b/includes/rts/storage/GC.h
index ddc4238592..387bd260d3 100644
--- a/includes/rts/storage/GC.h
+++ b/includes/rts/storage/GC.h
@@ -6,8 +6,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_STORAGE_GC_H
-#define RTS_STORAGE_GC_H
+#pragma once
 
 #include <stddef.h>
 #include "rts/OSThreads.h"
@@ -241,5 +240,3 @@ INLINE_HEADER void initBdescr(bdescr *bd, generation *gen, generation *dest)
     bd->gen_no  = gen->no;
     bd->dest_no = dest->no;
 }
-
-#endif /* RTS_STORAGE_GC_H */
diff --git a/includes/rts/storage/InfoTables.h b/includes/rts/storage/InfoTables.h
index 307aac371c..e732a30daf 100644
--- a/includes/rts/storage/InfoTables.h
+++ b/includes/rts/storage/InfoTables.h
@@ -6,8 +6,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef RTS_STORAGE_INFOTABLES_H
-#define RTS_STORAGE_INFOTABLES_H
+#pragma once
 
 /* ----------------------------------------------------------------------------
    Relative pointers
@@ -394,5 +393,3 @@ typedef struct StgConInfoTable_ {
 #else
 #define GET_PROF_DESC(info) ((info)->prof.closure_desc)
 #endif
-
-#endif /* RTS_STORAGE_INFOTABLES_H */
diff --git a/includes/rts/storage/MBlock.h b/includes/rts/storage/MBlock.h
index a8251c8c0b..9fbe92ec7d 100644
--- a/includes/rts/storage/MBlock.h
+++ b/includes/rts/storage/MBlock.h
@@ -9,8 +9,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_STORAGE_MBLOCK_H
-#define RTS_STORAGE_MBLOCK_H
+#pragma once
 
 extern W_ peak_mblocks_allocated;
 extern W_ mblocks_allocated;
@@ -31,5 +30,3 @@ extern void *getNextMBlock(void **state, void *mblock);
 // needed for HEAP_ALLOCED below
 extern SpinLock gc_alloc_block_sync;
 #endif
-
-#endif /* RTS_STORAGE_MBLOCK_H */
diff --git a/includes/rts/storage/TSO.h b/includes/rts/storage/TSO.h
index fd32919e9d..e50e336a32 100644
--- a/includes/rts/storage/TSO.h
+++ b/includes/rts/storage/TSO.h
@@ -6,8 +6,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTS_STORAGE_TSO_H
-#define RTS_STORAGE_TSO_H
+#pragma once
 
 /*
  * PROFILING info in a TSO
@@ -260,5 +259,3 @@ void dirty_STACK (Capability *cap, StgStack *stack);
 
 /* this is the NIL ptr for a TSO queue (e.g. runnable queue) */
 #define END_TSO_QUEUE  ((StgTSO *)(void*)&stg_END_TSO_QUEUE_closure)
-
-#endif /* RTS_STORAGE_TSO_H */
diff --git a/includes/stg/DLL.h b/includes/stg/DLL.h
index 8ab5d8c3d4..cf857a8682 100644
--- a/includes/stg/DLL.h
+++ b/includes/stg/DLL.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef __STGDLL_H__
-#define __STGDLL_H__ 1
+#pragma once
 
 #if defined(COMPILING_WINDOWS_DLL)
 #  if defined(x86_64_HOST_ARCH)
@@ -71,5 +70,3 @@
 #else
 #define DLL_IMPORT_STDLIB DLLIMPORT
 #endif
-
-#endif /* __STGDLL_H__ */
diff --git a/includes/stg/HaskellMachRegs.h b/includes/stg/HaskellMachRegs.h
index e95cefd822..37e687bc4e 100644
--- a/includes/stg/HaskellMachRegs.h
+++ b/includes/stg/HaskellMachRegs.h
@@ -12,8 +12,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef HASKELLMACHREGS_H
-#define HASKELLMACHREGS_H
+#pragma once
 
 /*
  * Defining NO_REGS causes no global registers to be used.  NO_REGS is
@@ -45,5 +44,3 @@
 #endif
 
 #include "MachRegs.h"
-
-#endif /* HASKELLMACHREGS_H */
diff --git a/includes/stg/MachRegs.h b/includes/stg/MachRegs.h
index 232ce03810..a0cf595505 100644
--- a/includes/stg/MachRegs.h
+++ b/includes/stg/MachRegs.h
@@ -12,8 +12,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef MACHREGS_H
-#define MACHREGS_H
+#pragma once
 
 /* This file is #included into Haskell code in the compiler: #defines
  * only in here please.
@@ -714,5 +713,3 @@ the stack. See Note [Overlapping global registers] for implications.
 #else
 #undef NO_ARG_REGS
 #endif
-
-#endif /* MACHREGS_H */
diff --git a/includes/stg/MiscClosures.h b/includes/stg/MiscClosures.h
index 9d907ab3ba..1181abcca4 100644
--- a/includes/stg/MiscClosures.h
+++ b/includes/stg/MiscClosures.h
@@ -17,8 +17,7 @@
  *
  * --------------------------------------------------------------------------*/
 
-#ifndef STGMISCCLOSURES_H
-#define STGMISCCLOSURES_H
+#pragma once
 
 #if IN_STG_CODE
 #  define RTS_RET_INFO(i)   extern W_(i)[]
@@ -532,5 +531,3 @@ void * pushCostCentre (void *ccs, void *cc);
 extern unsigned int n_capabilities;
 
 #endif
-
-#endif /* STGMISCCLOSURES_H */
diff --git a/includes/stg/Prim.h b/includes/stg/Prim.h
index 9872512701..fa3a3ec91f 100644
--- a/includes/stg/Prim.h
+++ b/includes/stg/Prim.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef PRIM_H
-#define PRIM_H
+#pragma once
 
 /* libraries/ghc-prim/cbits/atomic.c */
 StgWord hs_atomic_add8(StgWord x, StgWord val);
@@ -81,5 +80,3 @@ StgWord hs_ctz8(StgWord x);
 StgWord hs_ctz16(StgWord x);
 StgWord hs_ctz32(StgWord x);
 StgWord hs_ctz64(StgWord64 x);
-
-#endif /* PRIM_H */
diff --git a/includes/stg/Regs.h b/includes/stg/Regs.h
index 36324632d2..cf9e306504 100644
--- a/includes/stg/Regs.h
+++ b/includes/stg/Regs.h
@@ -11,8 +11,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef REGS_H
-#define REGS_H
+#pragma once
 
 /*
  * The STG machine has a collection of "registers", each one of which
@@ -527,5 +526,3 @@ GLOBAL_REG_DECL(bdescr *,HpAlloc,REG_HpAlloc)
 #define stg_gc_fun                (FunReg->stgGCFun)
 
 #endif /* IN_STG_CODE */
-
-#endif /* REGS_H */
diff --git a/includes/stg/RtsMachRegs.h b/includes/stg/RtsMachRegs.h
index 29262dc17a..5a0464b909 100644
--- a/includes/stg/RtsMachRegs.h
+++ b/includes/stg/RtsMachRegs.h
@@ -12,8 +12,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef RTSMACHREGS_H
-#define RTSMACHREGS_H
+#pragma once
 
 #ifdef UnregisterisedCompiler
 #ifndef NO_REGS
@@ -51,5 +50,3 @@
 #endif
 
 #include "MachRegs.h"
-
-#endif /* RTSMACHREGS_H */
diff --git a/includes/stg/SMP.h b/includes/stg/SMP.h
index 0e806b6716..e4ae6121fa 100644
--- a/includes/stg/SMP.h
+++ b/includes/stg/SMP.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef SMP_H
-#define SMP_H
+#pragma once
 
 #if arm_HOST_ARCH && defined(arm_HOST_ARCH_PRE_ARMv6)
 void arm_atomic_spin_lock(void);
@@ -299,5 +298,3 @@ atomic_dec(StgVolatilePtr p)
 #define VOLATILE_LOAD(p) ((StgWord)*((StgWord*)(p)))
 
 #endif /* !THREADED_RTS */
-
-#endif /* SMP_H */
diff --git a/includes/stg/Ticky.h b/includes/stg/Ticky.h
index 5143c2fd5c..1e16a1ae08 100644
--- a/includes/stg/Ticky.h
+++ b/includes/stg/Ticky.h
@@ -11,8 +11,7 @@
  *
  * -------------------------------------------------------------------------- */
 
-#ifndef TICKYCOUNTERS_H
-#define TICKYCOUNTERS_H
+#pragma once
 
 /* These should probably be automatically generated in order to
    keep them consistent with the macros that use them (which are
@@ -215,6 +214,3 @@ EXTERN StgInt RET_UNBOXED_TUP_hst[TICKY_BIN_COUNT] INIT({0});
 #define TICK_ALLOC_SE_THK(g,s)
 
 #endif
-
-
-#endif /* TICKYCOUNTERS_H */
diff --git a/includes/stg/Types.h b/includes/stg/Types.h
index 3a08eb2f85..af6a51791c 100644
--- a/includes/stg/Types.h
+++ b/includes/stg/Types.h
@@ -18,8 +18,7 @@
  *
  * ---------------------------------------------------------------------------*/
 
-#ifndef STGTYPES_H
-#define STGTYPES_H
+#pragma once
 
 #if defined(mingw32_HOST_OS)
 /* Inform mingw we want the ISO rather than Windows printf format specifiers. */
@@ -182,5 +181,3 @@ typedef StgWord8*          StgByteArray;
 
 typedef void  *(*(*StgFunPtr)(void))(void);
 typedef StgFunPtr StgFun(void);
-
-#endif /* STGTYPES_H */