docs/users_guide/runtime_control.rst

@@ -721,6 +721,18 @@ performance.
     the default small ``-A`` value is suboptimal, as it can be in
     programs that create large amounts of long-lived data.
 
+.. rts-flag:: --arbitrary-heap-start
+
+    :default: disabled
+    :since: 9.4
+
+    .. index::
+       single: arbitrary heap start
+
+    By default heap base offset for the garbage collector is selected above 0x200000000
+    because otherwise it can clash with third-party libraries.
+    When enabled this option relaxes this restriction.
+
 .. rts-flag:: -I ⟨seconds⟩
 
     :default: 0.3 seconds in the threaded runtime, 0 in the non-threaded runtime

hadrian/build-cabal

@@ -25,9 +25,9 @@ CABVER=( ${CABVERSTR//./ } )
 
 if [ "${CABVER[0]}" -gt 2 -o "${CABVER[0]}" -eq 2 -a "${CABVER[1]}" -ge 2 ];
 then
-    "$CABAL" --project-file="$PROJ" new-build "${CABFLAGS[@]}" -j exe:hadrian
+    "$CABAL" --allow-newer --project-file="$PROJ" new-build "${CABFLAGS[@]}" -j exe:hadrian
     # use new-exec instead of new-run to make sure that the build-tools (alex & happy) are in PATH
-    "$CABAL" --project-file="$PROJ" new-exec  "${CABFLAGS[@]}"    hadrian -- \
+    "$CABAL" --allow-newer --project-file="$PROJ" new-exec  "${CABFLAGS[@]}"    hadrian -- \
         --directory "$PWD" \
         "$@"
 else

hadrian/src/Settings/Packages.hs

@@ -327,6 +327,7 @@ rtsPackageArgs = package rts ? do
           , arg $ "-I" ++ path
 
           , notM targetSupportsSMP           ? arg "-DNOSMP"
+          , isOsxTarget ? arg "-march=armv8-a+norcpc"
 
           , Debug     `wayUnit` way          ? pure [ "-DDEBUG"
                                                     , "-fno-omit-frame-pointer"

libraries/base/src/GHC/RTS/Flags.hsc

@@ -144,6 +144,7 @@ data GCFlags = GCFlags
     , minOldGenSize         :: Word32
     , heapSizeSuggestion    :: Word32
     , heapSizeSuggestionAuto :: Bool
+    , arbitraryHeapStart    :: Bool
     , oldGenFactor          :: Double
     , returnDecayFactor     :: Double
     , pcFreeHeap            :: Double
@@ -462,6 +463,8 @@ getGCFlags = do
           <*> #{peek GC_FLAGS, heapSizeSuggestion} ptr
           <*> (toBool <$>
                 (#{peek GC_FLAGS, heapSizeSuggestionAuto} ptr :: IO CBool))
+          <*> (toBool <$>
+                (#{peek GC_FLAGS, arbitraryHeapStart} ptr :: IO CBool))
           <*> #{peek GC_FLAGS, oldGenFactor} ptr
           <*> #{peek GC_FLAGS, returnDecayFactor} ptr
           <*> #{peek GC_FLAGS, pcFreeHeap} ptr

rts/RtsFlags.c

@@ -162,6 +162,7 @@ void initRtsFlagsDefaults(void)
     RtsFlags.GcFlags.heapLimitGrace     = (1024 * 1024);
     RtsFlags.GcFlags.heapSizeSuggestion = 0;    /* none */
     RtsFlags.GcFlags.heapSizeSuggestionAuto = false;
+    RtsFlags.GcFlags.arbitraryHeapStart = false;
     RtsFlags.GcFlags.pcFreeHeap         = 3;    /* 3% */
     RtsFlags.GcFlags.oldGenFactor       = 2;
     RtsFlags.GcFlags.returnDecayFactor  = 4;
@@ -345,6 +346,10 @@ usage_text[] = {
 "  -xb<addr> Sets the address from which a suitable start for the heap memory",
 "            will be searched from. This is useful if the default address",
 "            clashes with some third-party library.",
+"  --arbitrary-heap-start",
+"            By default heap base offset for the garbage collector is selected above 0x200000000",
+"            because otherwise it can clash with third-party libraries.",
+"            When enabled this option relaxes this restriction.",
 "  -xn       Use the non-moving collector for the old generation.",
 "  -m<n>     Minimum % of heap which must be available (default 3%)",
 "  -G<n>     Number of generations (default: 2)",
@@ -1055,6 +1060,11 @@ error = true;
                        OPTION_UNSAFE;
                        RtsFlags.HpcFlags.writeTixFile = false;
                   }
+                  else if (strequal("arbitrary-heap-start",
+                               &rts_argv[arg][2])) {
+                      OPTION_UNSAFE;
+                      RtsFlags.GcFlags.arbitraryHeapStart = true;
+                  }
 #if defined(THREADED_RTS)
 #if defined(mingw32_HOST_OS)
                   else if (!strncmp("io-manager-threads",

rts/include/rts/Flags.h

@@ -49,6 +49,7 @@ typedef struct _GC_FLAGS {
     uint32_t     minOldGenSize;      /* in *blocks* */
     uint32_t     heapSizeSuggestion; /* in *blocks* */
     bool heapSizeSuggestionAuto;
+    bool arbitraryHeapStart;
     double  oldGenFactor;
     double  returnDecayFactor;
     double  pcFreeHeap;

rts/posix/OSMem.c

@@ -209,7 +209,7 @@ my_mmap (void *addr, W_ size, int operation)
         // not our problem though.
         errorBelch("memory allocation failed (requested %" FMT_Word " bytes)",
                    size);
-        stg_exit(EXIT_FAILURE);
+        return NULL;
     }
 
     if(operation & MEM_COMMIT) {
@@ -608,9 +608,11 @@ void *osReserveHeapMemory(void *startAddressPtr, W_ *len)
             // physical memory but a 511GB ulimit). See #14492.
             *len -= *len / 8;
             // debugBelch("Limit hit, reduced len: %zu\n", *len);
-        } else if ((W_)at >= minimumAddress) {
+        } else if (RtsFlags.GcFlags.arbitraryHeapStart || (W_)at >= minimumAddress) {
             // Success! We were given a block of memory starting above the 8 GB
             // mark, which is what we were looking for.
+            // Or we allow to allocate the block anywhere by setting
+            // arbitraryHeapStart flag.
 
             break;
         } else {