Enable new warning for bad CPP #if usagewip/erikd/rts

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.

12 files changed, 27 insertions, 23 deletions

diff --git a/rts/LinkerInternals.h b/rts/LinkerInternals.h
index 76497df257..9b4fc17e75 100644
--- a/rts/LinkerInternals.h
+++ b/rts/LinkerInternals.h
@@ -85,7 +85,8 @@ 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
 #define NEED_SYMBOL_EXTRAS 1
 #endif
 
diff --git a/rts/OldARMAtomic.c b/rts/OldARMAtomic.c
index 3c60e6d669..d639af1ecb 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/RtsUtils.c b/rts/RtsUtils.c
index 31dc060244..51453fd6fd 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
 
@@ -171,7 +171,7 @@ 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 a4d0c1da80..c092e43516 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/posix/GetTime.c b/rts/posix/GetTime.c
index 4d25795948..a5d4c25a35 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..cfacd65cdc 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/sm/CNF.c b/rts/sm/CNF.c
index 7dfaced7ef..c24accd005 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