Enable new warning for fragile/incorrect CPP #if usage

The C code in the RTS now gets built with `-Wundef` and the Haskell code
(stages 1 and 2 only) with `-Wcpp-undef`. We now get warnings whereever
`#if` is used on undefined identifiers.

Test Plan: Validate on Linux and Windows

Reviewers: austin, angerman, simonmar, bgamari, Phyx

Reviewed By: bgamari

Subscribers: thomie, snowleopard

Differential Revision: https://phabricator.haskell.org/D3278

16 files changed, 43 insertions, 37 deletions

diff --git a/rts/LinkerInternals.h b/rts/LinkerInternals.h
index 16fbab2b29..a04db77b92 100644
--- a/rts/LinkerInternals.h
+++ b/rts/LinkerInternals.h
@@ -91,7 +91,8 @@ typedef struct ForeignExportStablePtr_ {
     struct ForeignExportStablePtr_ *next;
 } ForeignExportStablePtr;
 
-#if powerpc_HOST_ARCH || x86_64_HOST_ARCH || arm_HOST_ARCH
+#if defined(powerpc_HOST_ARCH) || defined(x86_64_HOST_ARCH) \
+    || defined(arm_HOST_ARCH)
 /* ios currently uses adjacent got tables, and no symbol extras */
 #if !defined(ios_HOST_OS)
 #define NEED_SYMBOL_EXTRAS 1
@@ -102,17 +103,17 @@ typedef struct ForeignExportStablePtr_ {
  * address relocations on the PowerPC, x86_64 and ARM.
  */
 typedef struct {
-#ifdef powerpc_HOST_ARCH
+#if defined(powerpc_HOST_ARCH)
     struct {
         short lis_r12, hi_addr;
         short ori_r12_r12, lo_addr;
         long mtctr_r12;
         long bctr;
     } jumpIsland;
-#elif x86_64_HOST_ARCH
+#elif defined(x86_64_HOST_ARCH)
     uint64_t    addr;
     uint8_t     jumpIsland[6];
-#elif arm_HOST_ARCH
+#elif defined(arm_HOST_ARCH)
     uint8_t     jumpIsland[16];
 #endif
 } SymbolExtra;
@@ -283,7 +284,7 @@ ObjectCode* mkOc( pathchar *path, char *image, int imageSize,
                   int misalignment
                   );
 
-#if defined (mingw32_HOST_OS)
+#if defined(mingw32_HOST_OS)
 /* We use myindex to calculate array addresses, rather than
    simply doing the normal subscript thing.  That's because
    some of the above structs have sizes which are not
diff --git a/rts/OldARMAtomic.c b/rts/OldARMAtomic.c
index 3c60e6d669..e76f4c6354 100644
--- a/rts/OldARMAtomic.c
+++ b/rts/OldARMAtomic.c
@@ -20,7 +20,7 @@
 #include <sched.h>
 #endif
 
-#if arm_HOST_ARCH && defined(arm_HOST_ARCH_PRE_ARMv6)
+#if defined(arm_HOST_ARCH) && defined(arm_HOST_ARCH_PRE_ARMv6)
 
 static volatile int atomic_spin = 0;
 
diff --git a/rts/PrimOps.cmm b/rts/PrimOps.cmm
index 4baf63a8f7..37eee439ac 100644
--- a/rts/PrimOps.cmm
+++ b/rts/PrimOps.cmm
@@ -561,7 +561,7 @@ stg_atomicModifyMutVarzh ( gcptr mv, gcptr f )
          r = [stg_sel_1 z]   (max (HS + 1) MIN_UPD_SIZE)
     */
 
-#if MIN_UPD_SIZE > 1
+#if defined(MIN_UPD_SIZE) && MIN_UPD_SIZE > 1
 #define THUNK_1_SIZE (SIZEOF_StgThunkHeader + WDS(MIN_UPD_SIZE))
 #define TICK_ALLOC_THUNK_1() TICK_ALLOC_UP_THK(WDS(1),WDS(MIN_UPD_SIZE-1))
 #else
@@ -569,7 +569,7 @@ stg_atomicModifyMutVarzh ( gcptr mv, gcptr f )
 #define TICK_ALLOC_THUNK_1() TICK_ALLOC_UP_THK(WDS(1),0)
 #endif
 
-#if MIN_UPD_SIZE > 2
+#if defined(MIN_UPD_SIZE) && MIN_UPD_SIZE > 2
 #define THUNK_2_SIZE (SIZEOF_StgThunkHeader + WDS(MIN_UPD_SIZE))
 #define TICK_ALLOC_THUNK_2() TICK_ALLOC_UP_THK(WDS(2),WDS(MIN_UPD_SIZE-2))
 #else
diff --git a/rts/RtsUtils.c b/rts/RtsUtils.c
index 85f951addd..996d28ac4c 100644
--- a/rts/RtsUtils.c
+++ b/rts/RtsUtils.c
@@ -22,7 +22,7 @@
 /* HACK: On Mac OS X 10.4 (at least), time.h doesn't declare ctime_r with
  *       _POSIX_C_SOURCE. If this is the case, we declare it ourselves.
  */
-#if HAVE_CTIME_R && !HAVE_DECL_CTIME_R
+#if defined(HAVE_CTIME_R) && !HAVE_DECL_CTIME_R
 extern char *ctime_r(const time_t *, char *);
 #endif
 
@@ -164,7 +164,7 @@ time_str(void)
 
     if (now == 0) {
         time(&now);
-#if HAVE_CTIME_R
+#if defined(HAVE_CTIME_R)
         ctime_r(&now, nowstr);
 #else
         strcpy(nowstr, ctime(&now));
diff --git a/rts/Schedule.c b/rts/Schedule.c
index b77e7a21ef..296461b38d 100644
--- a/rts/Schedule.c
+++ b/rts/Schedule.c
@@ -411,7 +411,7 @@ run_thread:
     prev_what_next = t->what_next;
 
     errno = t->saved_errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
     SetLastError(t->saved_winerror);
 #endif
 
@@ -490,7 +490,7 @@ run_thread:
     // XXX: possibly bogus for SMP because this thread might already
     // be running again, see code below.
     t->saved_errno = errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
     // Similarly for Windows error code
     t->saved_winerror = GetLastError();
 #endif
@@ -2374,12 +2374,12 @@ suspendThread (StgRegTable *reg, bool interruptible)
   int saved_errno;
   StgTSO *tso;
   Task *task;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
   StgWord32 saved_winerror;
 #endif
 
   saved_errno = errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
   saved_winerror = GetLastError();
 #endif
 
@@ -2419,7 +2419,7 @@ suspendThread (StgRegTable *reg, bool interruptible)
   RELEASE_LOCK(&cap->lock);
 
   errno = saved_errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
   SetLastError(saved_winerror);
 #endif
   return task;
@@ -2433,12 +2433,12 @@ resumeThread (void *task_)
     Capability *cap;
     Task *task = task_;
     int saved_errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
     StgWord32 saved_winerror;
 #endif
 
     saved_errno = errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
     saved_winerror = GetLastError();
 #endif
 
@@ -2475,7 +2475,7 @@ resumeThread (void *task_)
     cap->r.rCurrentTSO = tso;
     cap->in_haskell = true;
     errno = saved_errno;
-#if mingw32_HOST_OS
+#ifdef mingw32_HOST_OS
     SetLastError(saved_winerror);
 #endif
 
diff --git a/rts/Threads.c b/rts/Threads.c
index f5eb9d360c..9cfd36a7c9 100644
--- a/rts/Threads.c
+++ b/rts/Threads.c
@@ -826,7 +826,7 @@ loop:
  * Debugging: why is a thread blocked
  * ------------------------------------------------------------------------- */
 
-#if DEBUG
+#ifdef DEBUG
 void
 printThreadBlockage(StgTSO *tso)
 {
diff --git a/rts/ghc.mk b/rts/ghc.mk
index b756d942ca..e24e199598 100644
--- a/rts/ghc.mk
+++ b/rts/ghc.mk
@@ -267,7 +267,10 @@ WARNING_OPTS += -Waggregate-return
 WARNING_OPTS += -Wpointer-arith
 WARNING_OPTS += -Wmissing-noreturn
 WARNING_OPTS += -Wnested-externs
-WARNING_OPTS += -Wredundant-decls 
+WARNING_OPTS += -Wredundant-decls
+ifeq "$(GccLT46)" "NO"
+WARNING_OPTS += -Wundef
+endif
 
 # These ones are hard to avoid:
 #WARNING_OPTS += -Wconversion
diff --git a/rts/linker/MachO.c b/rts/linker/MachO.c
index 16b712a804..a7c9189250 100644
--- a/rts/linker/MachO.c
+++ b/rts/linker/MachO.c
@@ -248,7 +248,8 @@ ocVerifyImage_MachO(ObjectCode * oc)
 
     IF_DEBUG(linker, debugBelch("ocVerifyImage_MachO: start\n"));
 
-#if x86_64_HOST_ARCH || powerpc64_HOST_ARCH || aarch64_HOST_ARCH
+#if defined(x86_64_HOST_ARCH) || defined(powerpc64_HOST_ARCH) \
+    || defined(aarch64_HOST_ARCH)
     if(header->magic != MH_MAGIC_64) {
         errorBelch("Could not load image %s: bad magic!\n"
                    "  Expected %08x (64bit), got %08x%s\n",
@@ -281,7 +282,7 @@ resolveImports(
 
     IF_DEBUG(linker, debugBelch("resolveImports: start\n"));
 
-#if i386_HOST_ARCH
+#if defined(i386_HOST_ARCH)
     int isJumpTable = 0;
 
     if (strcmp(sect->sectname,"__jump_table") == 0) {
@@ -319,7 +320,7 @@ resolveImports(
         }
         ASSERT(addr);
 
-#if i386_HOST_ARCH
+#if defined(i386_HOST_ARCH)
         if (isJumpTable) {
             checkProddableBlock(oc,oc->image + sect->offset + i*itemSize, 5);
 
@@ -1922,7 +1923,8 @@ machoGetMisalignment( FILE * f )
     }
     fseek(f, -sizeof(header), SEEK_CUR);
 
-#if x86_64_HOST_ARCH || powerpc64_HOST_ARCH || aarch64_HOST_ARCH
+#if defined(x86_64_HOST_ARCH) || defined(powerpc64_HOST_ARCH) \
+    || defined(aarch64_HOST_ARCH)
     if(header.magic != MH_MAGIC_64) {
         barf("Bad magic. Expected: %08x, got: %08x.",
              MH_MAGIC_64, header.magic);
diff --git a/rts/posix/GetTime.c b/rts/posix/GetTime.c
index 4d25795948..5be9c8e350 100644
--- a/rts/posix/GetTime.c
+++ b/rts/posix/GetTime.c
@@ -190,7 +190,7 @@ void getUnixEpochTime(StgWord64 *sec, StgWord32 *nsec)
 W_
 getPageFaults(void)
 {
-#if !defined(HAVE_GETRUSAGE) || haiku_HOST_OS
+#if !defined(HAVE_GETRUSAGE) || defined(haiku_HOST_OS)
     return 0;
 #else
     struct rusage t;
diff --git a/rts/posix/OSMem.c b/rts/posix/OSMem.c
index dcf734f19d..48b154fa11 100644
--- a/rts/posix/OSMem.c
+++ b/rts/posix/OSMem.c
@@ -39,7 +39,7 @@
 
 #include <errno.h>
 
-#if darwin_HOST_OS || ios_HOST_OS
+#if defined(darwin_HOST_OS) || defined(ios_HOST_OS)
 #include <mach/mach.h>
 #include <mach/vm_map.h>
 #include <sys/sysctl.h>
@@ -114,7 +114,7 @@ my_mmap (void *addr, W_ size, int operation)
 {
     void *ret;
 
-#if darwin_HOST_OS
+#ifdef darwin_HOST_OS
     // Without MAP_FIXED, Apple's mmap ignores addr.
     // With MAP_FIXED, it overwrites already mapped regions, whic
     // mmap(0, ... MAP_FIXED ...) is worst of all: It unmaps the program text
@@ -170,9 +170,9 @@ my_mmap (void *addr, W_ size, int operation)
     else
         flags = 0;
 
-#if hpux_HOST_OS
+#ifdef hpux_HOST_OS
     ret = mmap(addr, size, prot, flags | MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
-#elif linux_HOST_OS
+#elif defined(linux_HOST_OS)
     ret = mmap(addr, size, prot, flags | MAP_ANON | MAP_PRIVATE, -1, 0);
     if (ret == (void *)-1 && errno == EPERM) {
         // Linux may return EPERM if it tried to give us
diff --git a/rts/posix/OSThreads.c b/rts/posix/OSThreads.c
index 45f394208f..465c8675a3 100644
--- a/rts/posix/OSThreads.c
+++ b/rts/posix/OSThreads.c
@@ -137,7 +137,7 @@ createOSThread (OSThreadId* pId, char *name STG_UNUSED,
   int result = pthread_create(pId, NULL, (void *(*)(void *))startProc, param);
   if (!result) {
     pthread_detach(*pId);
-#if HAVE_PTHREAD_SETNAME_NP
+#ifdef HAVE_PTHREAD_SETNAME_NP
     pthread_setname_np(*pId, name);
 #endif
   }
diff --git a/rts/posix/itimer/Pthread.c b/rts/posix/itimer/Pthread.c
index 3b31fe4103..5c708ecf4d 100644
--- a/rts/posix/itimer/Pthread.c
+++ b/rts/posix/itimer/Pthread.c
@@ -65,7 +65,7 @@
 #include <unistd.h>
 #include <fcntl.h>
 
-#if HAVE_SYS_TIMERFD_H
+#ifdef HAVE_SYS_TIMERFD_H
 #include <sys/timerfd.h>
 #define USE_TIMERFD_FOR_ITIMER 1
 #else
@@ -101,7 +101,7 @@ static void *itimer_thread_func(void *_handle_tick)
     uint64_t nticks;
     int timerfd = -1;
 
-#if USE_TIMERFD_FOR_ITIMER
+#if defined(USE_TIMERFD_FOR_ITIMER) && USE_TIMERFD_FOR_ITIMER
     struct itimerspec it;
     it.it_value.tv_sec  = TimeToSeconds(itimer_interval);
     it.it_value.tv_nsec = TimeToNS(itimer_interval) % 1000000000;
@@ -169,7 +169,7 @@ initTicker (Time interval, TickProc handle_tick)
      * to the thread we create so we can later join to it if requested
      */
     if (! pthread_create(&thread, NULL, itimer_thread_func, (void*)handle_tick)) {
-#if HAVE_PTHREAD_SETNAME_NP
+#ifdef HAVE_PTHREAD_SETNAME_NP
         pthread_setname_np(thread, "ghc_ticker");
 #endif
     } else {
diff --git a/rts/sm/CNF.c b/rts/sm/CNF.c
index 624dba30b2..af90718b4f 100644
--- a/rts/sm/CNF.c
+++ b/rts/sm/CNF.c
@@ -1170,7 +1170,7 @@ compactFixupPointers(StgCompactNFData *str,
     dbl_link_onto(bd, &g0->compact_objects);
     RELEASE_SM_LOCK;
 
-#if DEBUG
+#ifdef DEBUG
     if (root)
         verify_consistency_loop(str);
 #endif
diff --git a/rts/sm/GCUtils.c b/rts/sm/GCUtils.c
index 9fda2fe070..3717faebed 100644
--- a/rts/sm/GCUtils.c
+++ b/rts/sm/GCUtils.c
@@ -346,7 +346,7 @@ alloc_todo_block (gen_workspace *ws, uint32_t size)
  * Debugging
  * -------------------------------------------------------------------------- */
 
-#if DEBUG
+#ifdef DEBUG
 void
 printMutableList(bdescr *bd)
 {
diff --git a/rts/sm/GCUtils.h b/rts/sm/GCUtils.h
index 3092262af6..3ea762376a 100644
--- a/rts/sm/GCUtils.h
+++ b/rts/sm/GCUtils.h
@@ -52,7 +52,7 @@ isPartiallyFull(bdescr *bd)
 }
 
 
-#if DEBUG
+#ifdef DEBUG
 void printMutableList (bdescr *bd);
 #endif
 
diff --git a/rts/sm/MBlock.c b/rts/sm/MBlock.c
index f6640d173c..833dd8c7c2 100644
--- a/rts/sm/MBlock.c
+++ b/rts/sm/MBlock.c
@@ -657,7 +657,7 @@ initMBlocks(void)
 #ifdef USE_LARGE_ADDRESS_SPACE
     {
         W_ size;
-#if aarch64_HOST_ARCH
+#ifdef aarch64_HOST_ARCH
         size = (W_)1 << 38; // 1/4 TByte
 #else
         size = (W_)1 << 40; // 1 TByte