configure: Add script code to force USE_MMAP for some targets

(Apply part of commit 21a49a9 from 'gcc_boehmgc' branch)

* configure.ac (gc_use_mmap): New variable (blank currently); add
comment and FIXME.
* configure.ac (USE_MMAP): Force define in case of gc_use_mmap is yes.

diff --git a/configure.ac b/configure.ac
index 4ccc59a90d6c2f427ebf31995bf461d822e8221b..4142c0463a33497e922ea500f806671f8bd5c4d5 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -39,6 +39,10 @@ AC_PROG_INSTALL
 # Special CFLAGS to use when building
 gc_cflags=""
 
+# gc_use_mmap   Set to "yes" on platforms where mmap should be used instead
+#               of sbrk. This will define USE_MMAP.
+gc_use_mmap=""
+
 # We should set -fexceptions if we are using gcc and might be used
 # inside something like gcj.  This is the zeroth approximation:
 if test :"$GCC": = :yes: ; then
@@ -55,6 +59,13 @@ else
     esac
 fi
 
+case "${host}" in
+  *-linux*)
+    # FIXME: This seems to be no longer needed as configured in gcconfig.h
+    #gc_use_mmap=yes
+    ;;
+esac
+
 #   target_optspace     --enable-target-optspace ("yes", "no", "")
 case "${target_optspace}:${host}" in
   yes:*)
@@ -780,6 +791,11 @@ if test "${enable_munmap}" != ""; then
     fi
     AC_DEFINE_UNQUOTED([MUNMAP_THRESHOLD], [${MUNMAP_THRESHOLD}],
         [Number of GC cycles to wait before unmapping an unused block.])
+else
+    if test "${gc_use_mmap}" = "yes"; then
+      AC_DEFINE([USE_MMAP], 1,
+                [Define to use mmap instead of sbrk to expand the heap.])
+    fi
 fi
 
 AM_CONDITIONAL(USE_LIBDIR, test -z "$with_cross_host")