diff --git a/configure.ac b/configure.ac
index 57848bb..09b9dad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -64,7 +64,7 @@ AC_TYPE_GETGROUPS
 AC_FUNC_MMAP
 
 AC_CHECK_FUNCS(strerror strtol lstat setrlimit sigrelse sighold sigaction \
-sysconf sigsetjmp getrusage)
+sysconf sigsetjmp getrusage mmap mprotect)
 
 AC_CACHE_CHECK(whether getenv can be redefined, es_cv_local_getenv,
 [if test "$ac_cv_header_stdlib_h" = no || test "$ac_cv_header_stdc" = no; then
diff --git a/gc.c b/gc.c
index a5ab0db..946ee31 100644
--- a/gc.c
+++ b/gc.c
@@ -56,85 +56,24 @@ static size_t minspace = MIN_minspace;	/* minimum number of bytes in a new space
 #define	VERBOSE(p)	NOP
 #endif
 
-
-/*
- * GCPROTECT
- *	to use the GCPROTECT option, you must provide the following functions
- *		initmmu
- *		take
- *		release
- *		invalidate
- *		revalidate
- *	for your operating system
- */
+#ifndef	MAP_ANONYMOUS
+#ifdef	MAP_ANON
+#define	MAP_ANONYMOUS	MAP_ANON
+#endif
+#endif
 
 #if GCPROTECT
-#if __MACH__
-
-/* mach versions of mmu operations */
-
-#include <mach.h>
-#include <mach_error.h>
-
-#define	PAGEROUND(n)	((n) + vm_page_size - 1) &~ (vm_page_size - 1)
-
-/* initmmu -- initialization for memory management calls */
-static void initmmu(void) {
-}
-
-/* take -- allocate memory for a space */
-static void *take(size_t n) {
-	vm_address_t addr;
-	kern_return_t error = vm_allocate(task_self(), &addr, n, TRUE);
-	if (error != KERN_SUCCESS) {
-		mach_error("vm_allocate", error);
-		esexit(1);
-	}
-	memset((void *) addr, 0xC9, n);
-	return (void *) addr;
-}
-
-/* release -- deallocate a range of memory */
-static void release(void *p, size_t n) {
-	kern_return_t error = vm_deallocate(task_self(), (vm_address_t) p, n);
-	if (error != KERN_SUCCESS) {
-		mach_error("vm_deallocate", error);
-		esexit(1);
-	}
-}
-
-/* invalidate -- disable access to a range of memory */
-static void invalidate(void *p, size_t n) {
-	kern_return_t error = vm_protect(task_self(), (vm_address_t) p, n, FALSE, 0);
-	if (error != KERN_SUCCESS) {
-		mach_error("vm_protect 0", error);
-		esexit(1);
-	}
-}
-
-/* revalidate -- enable access to a range of memory */
-static void revalidate(void *p, size_t n) {
-	kern_return_t error =
-		vm_protect(task_self(), (vm_address_t) p, n, FALSE, VM_PROT_READ|VM_PROT_WRITE);
-	if (error != KERN_SUCCESS) {
-		mach_error("vm_protect VM_PROT_READ|VM_PROT_WRITE", error);
-		esexit(1);
-	}
-	memset(p, 0x4F, n);
-}
-
-#else /* !__MACH__ */
-
-/* sunos-derived mmap(2) version of mmu operations */
-
+#if HAVE_MMAP
 #include <sys/mman.h>
+#endif
 
 static int pagesize;
 #define	PAGEROUND(n)	((n) + pagesize - 1) &~ (pagesize - 1)
 
 /* take -- allocate memory for a space */
 static void *take(size_t n) {
-	caddr_t addr;
+	void *addr;
+#if HAVE_MMAP
 #ifdef MAP_ANONYMOUS
 	addr = mmap(0, n, PROT_READ|PROT_WRITE,	MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
 #else
@@ -143,28 +82,40 @@ static void *take(size_t n) {
 		devzero = eopen("/dev/zero", oOpen);
 	addr = mmap(0, n, PROT_READ|PROT_WRITE, MAP_PRIVATE, devzero, 0);
 #endif
-	if (addr == (caddr_t) -1)
+	if (addr == MAP_FAILED)
 		panic("mmap: %s", esstrerror(errno));
+#else	/* !HAVE_MMAP */
+	addr = ealloc(n);
+#endif
 	memset(addr, 0xA5, n);
 	return addr;
 }
 
 /* release -- deallocate a range of memory */
 static void release(void *p, size_t n) {
+#if HAVE_MMAP
 	if (munmap(p, n) == -1)
 		panic("munmap: %s", esstrerror(errno));
+#else
+	efree(p);
+#endif
 }
 
 /* invalidate -- disable access to a range of memory */
 static void invalidate(void *p, size_t n) {
+	memset(p, 0x5e, n);
+#if HAVE_MMAP && HAVE_MPROTECT
 	if (mprotect(p, n, PROT_NONE) == -1)
 		panic("mprotect(PROT_NONE): %s", esstrerror(errno));
+#endif
 }
 
 /* revalidate -- enable access to a range of memory */
 static void revalidate(void *p, size_t n) {
+#if HAVE_MMAP && HAVE_MPROTECT
 	if (mprotect(p, n, PROT_READ|PROT_WRITE) == -1)
 		panic("mprotect(PROT_READ|PROT_WRITE): %s", esstrerror(errno));
+#endif
 }
 
 /* initmmu -- initialization for memory management calls */
@@ -175,8 +126,6 @@ static void initmmu(void) {
 	pagesize = getpagesize();
 #endif
 }
-
-#endif	/* !__MACH__ */
 #endif	/* GCPROTECT */
 
 
@@ -194,7 +143,7 @@ static Space *mkspace(Space *space, Space *next) {
 		Space *sp;
 		if (space->bot == NULL)
 			sp = NULL;
-		else if (SPACESIZE(space) < minspace)
+		else if ((size_t) SPACESIZE(space) < minspace)
 			sp = space;
 		else {
 			sp = space->next;
@@ -302,8 +251,8 @@ extern void globalroot(void *addr) {
 
 /* exceptionroot -- add an exception to the list of rooted exceptions */
 extern void exceptionroot(Root *root, List **e) {
-	Root *r;
 #if ASSERTIONS
+	Root *r;
 	for (r = exceptionrootlist; r != NULL; r = r->next)
 		assert(r->p != (void **)e);
 #endif
diff --git a/input.c b/input.c
index f187766..13b7f26 100644
--- a/input.c
+++ b/input.c
@@ -227,7 +227,7 @@ static int getverbose(Input *in) {
 }
 
 /* eoffill -- report eof when called to fill input buffer */
-static int eoffill(Input *in) {
+static int eoffill(Input UNUSED *in) {
 	assert(in->fd == -1);
 	return EOF;
 }
diff --git a/main.c b/main.c
index 9f5abaf..e7e6cb0 100644
--- a/main.c
+++ b/main.c
@@ -82,6 +82,8 @@ static Noreturn usage(void) {
 		"	-p	don't load functions from the environment\n"
 		"	-o	don't open stdin, stdout, and stderr if they were closed\n"
 		"	-d	don't ignore SIGQUIT or SIGTERM\n"
+	);
+	eprint(""
 #if GCINFO
 		"	-I	print garbage collector information\n"
 #endif
@@ -109,8 +111,8 @@ int main(int argc, char **argv0) {
 	Boolean keepclosed = FALSE;		/* -o */
 	Ref(const char *volatile, cmd, NULL);	/* -c */
 
-	initgc();
 	initconv();
+	initgc();
 
 	if (argc == 0) {
 		argc = 1;
diff --git a/match.c b/match.c
index d419c8f..1204cb6 100644
--- a/match.c
+++ b/match.c
@@ -28,7 +28,7 @@ static int rangematch(const char *p, const char *q, char c) {
 	Boolean neg;
 	Boolean matched = FALSE;
 	Boolean advanceq = (q != QUOTED && q != UNQUOTED);
-#define QX(expr) (advanceq ? (expr) : (void)0)
+#define QX(expr) (advanceq ? (expr) : 0)
 	if (*p == '~' && !ISQUOTED(q, 0)) {
 		p++, QX(q++);
 	    	neg = TRUE;
diff --git a/prim.c b/prim.c
index 13a66ae..74d7866 100644
--- a/prim.c
+++ b/prim.c
@@ -6,11 +6,11 @@
 static Dict *prims;
 
 extern List *prim(char *s, List *list, Binding *binding, int evalflags) {
-	List *(*p)(List *, Binding *, int);
-	p = (List *(*)(List *, Binding *, int)) dictget(prims, s);
+	Prim *p;
+	p = (Prim *) dictget(prims, s);
 	if (p == NULL)
 		fail("es:prim", "unknown primitive: %s", s);
-	return (*p)(list, binding, evalflags);
+	return (p->prim)(list, binding, evalflags);
 }
 
 static char *list_prefix;
diff --git a/prim.h b/prim.h
index 68e346b..a6a0db0 100644
--- a/prim.h
+++ b/prim.h
@@ -1,12 +1,16 @@
 /* prim.h -- definitions for es primitives ($Revision: 1.1.1.1 $) */
 
+typedef struct { List *(*prim)(List *, Binding *, int); } Prim;
+
 #define	PRIM(name)	static List *CONCAT(prim_,name)( \
 				List UNUSED *list, Binding UNUSED *binding, int UNUSED evalflags \
 			)
-#define	X(name)		(primdict = dictput( \
+#define	X(name)		STMT( \
+			static Prim CONCAT(prim_struct_,name) = { CONCAT(prim_,name) }; \
+			primdict = dictput( \
 				primdict, \
 				STRING(name), \
-				(void *) CONCAT(prim_,name) \
+				(void *) &CONCAT(prim_struct_,name) \
 			))
 
 extern Dict *initprims_controlflow(Dict *primdict);	/* prim-ctl.c */
diff --git a/print.c b/print.c
index 87cb40a..f0efcd1 100644
--- a/print.c
+++ b/print.c
@@ -263,6 +263,10 @@ extern int printfmt(Format *format, const char *fmt) {
  * the public entry points
  */
 
+#ifndef va_copy
+#define	va_copy	__va_copy
+#endif
+
 extern int fmtprint VARARGS2(Format *, format, const char *, fmt) {
 	int n = -format->flushed;
 #if NO_VA_LIST_ASSIGN
diff --git a/stdenv.h b/stdenv.h
index 8caab1c..98bfbf8 100644
--- a/stdenv.h
+++ b/stdenv.h
@@ -165,6 +165,11 @@ extern void *qsort(
 #define STRING(s)	#s
 #endif
 
+/* this is not a principled fallback, but it should work on most systems */
+#ifndef NSIG
+#define NSIG 64
+#endif
+
 
 /*
  * types we use throughout es
diff --git a/var.c b/var.c
index 9421965..a2f50e2 100644
--- a/var.c
+++ b/var.c
@@ -114,6 +114,8 @@ static Boolean isexported(const char *name) {
 
 /* setnoexport -- mark a list of variable names not for export */
 extern void setnoexport(List *list) {
+	static char noexportchar = '!';
+
 	isdirty = TRUE;
 	if (list == NULL) {
 		noexport = NULL;
@@ -121,7 +123,7 @@ extern void setnoexport(List *list) {
 	}
 	gcdisable();
 	for (noexport = mkdict(); list != NULL; list = list->next)
-		noexport = dictput(noexport, getstr(list->term), (void *) setnoexport);
+		noexport = dictput(noexport, getstr(list->term), &noexportchar);
 	gcenable();
 }