use mremap where available

[Clint Adams <clint@xxxxxxx>]

I'm not committing this.

Index: configure.ac
===================================================================
RCS file: /cvsroot/zsh/zsh/configure.ac,v
retrieving revision 1.18
diff -u -r1.18 configure.ac
--- configure.ac	8 Jun 2004 13:34:12 -0000	1.18
+++ configure.ac	16 Jul 2004 19:12:28 -0000
@@ -1129,7 +1129,7 @@
 
 AC_FUNC_MMAP
 if test x$ac_cv_func_mmap_fixed_mapped = xyes; then
-  AC_CHECK_FUNCS(munmap msync)
+  AC_CHECK_FUNCS(munmap msync mremap)
 fi
 
 if test $ac_cv_func_setpgrp = yes; then
Index: Src/mem.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/mem.c,v
retrieving revision 1.11
diff -u -r1.11 mem.c
--- Src/mem.c	2 Jun 2004 22:14:26 -0000	1.11
+++ Src/mem.c	16 Jul 2004 19:12:29 -0000
@@ -493,6 +493,13 @@
 	    n -= n % HEAPSIZE;
 
 #ifdef USE_MMAP
+# if defined(HAVE_MREMAP) && defined(MREMAP_MAYMOVE)
+	    size_t pgsz = sysconf(_SC_PAGESIZE);     /* SVR4 */
+	    h = (Heap) mremap(h, h->size, (n + pgsz-1) & ~(pgsz-1), MREMAP_MAYMOVE);
+	    if (errno)
+		    zwarn("mremap: %e", NULL, errno);
+	    DPUTS((h == MAP_FAILED), "BUG: mremap failed");
+# else
 	    {
 		/*
 		 * I don't know any easy portable way of requesting
@@ -507,6 +514,7 @@
 		munmap((void *)h, h->size);
 		h = hnew;
 	    }
+# endif
 #else
 	    h = (Heap) realloc(h, n);
 #endif