diff --git a/modules/src/system/aprintf.c b/modules/src/system/aprintf.c
new file mode 100644
index 000000000..997d408c2
--- /dev/null
+++ b/modules/src/system/aprintf.c
@@ -0,0 +1,28 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include "system.h"
+
+char* aprintf(const char* fmt, ...)
+{
+    int n;
+    char* p;
+    va_list ap;
+
+    va_start(ap, fmt);
+    n = vsnprintf(NULL, 0, fmt, ap) + 1;
+    va_end(ap);
+
+    p = malloc(n);
+    if (!p)
+        return NULL;
+
+    va_start(ap, fmt);
+    vsnprintf(p, n, fmt, ap);
+    va_end(ap);
+
+    return p;
+}
+
+/* vim: set sw=4 ts=4 expandtab : */
+
diff --git a/modules/src/system/build.lua b/modules/src/system/build.lua
index 343c60fb3..c19a82924 100644
--- a/modules/src/system/build.lua
+++ b/modules/src/system/build.lua
@@ -1,17 +1,30 @@
 clibrary {
 	name = "lib",
 	srcs = {
-		"./access.c", "./break.c", "./chmode.c", "./close.c",
-		"./create.c", "./filesize.c","./basename.c","./tmpnam.c",
-		--"./lock.c",
-		"./modtime.c", "./open.c", "./read.c", "./remove.c",
-		"./rename.c", "./seek.c", "./stop.c", "./system.c",
-		--"./unlock.c”,
-		"./write.c",
-		"./tmpdir.c",
-		"./syssystem.c",
-		"./strndup.c",
+		"./access.c",
+		"./aprintf.c",
+		"./basename.c",
+		"./break.c",
+		"./chmode.c",
+		"./close.c",
+		"./create.c",
+		"./filesize.c",
+		"./maketempfile.c",
+		"./modtime.c",
+		"./open.c",
+		"./read.c",
+		"./remove.c",
+		"./rename.c",
+		"./seek.c",
 		"./setbinarymode.c",
+		"./stop.c",
+		"./strndup.c",
+		"./syssystem.c",
+		"./system.c",
+		"./tmpdir.c",
+		"./write.c",
+		--"./lock.c",
+		--"./unlock.c”,
 	},
 	hdrs = { "./system.h" },
 }
diff --git a/modules/src/system/maketempfile.c b/modules/src/system/maketempfile.c
new file mode 100644
index 000000000..02068b628
--- /dev/null
+++ b/modules/src/system/maketempfile.c
@@ -0,0 +1,52 @@
+/*  Copyright (c) 2022. See the file License in
+ *  the root directory for more information.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <time.h>
+#include <fcntl.h>
+#include <errno.h>
+#include "system.h"
+
+#if defined WIN32
+static unsigned temper(unsigned x)
+{
+	x ^= x>>11;
+	x ^= x<<7 & 0x9D2C5680;
+	x ^= x<<15 & 0xEFC60000;
+	x ^= x>>18;
+	return x;
+}
+
+static int rand_r(unsigned *seed)
+{
+	return temper(*seed = *seed * 1103515245 + 12345)/2;
+}
+#endif
+
+char* sys_maketempfile(const char* prefix, const char* suffix)
+{
+	struct timespec ts;
+	clock_gettime(CLOCK_REALTIME, &ts);
+
+	unsigned int seed = (unsigned int)(uintptr_t)prefix
+		^ (unsigned int)ts.tv_sec ^ (unsigned int)ts.tv_nsec;
+	const char* tempdir = sys_gettmpdir();
+
+	for (;;)
+	{
+		unsigned int hash = rand_r(&seed);
+		char* filename = aprintf("%s/ack-%s-%x%s",
+			tempdir, prefix, hash,
+			suffix);
+		int fd = open(filename, O_CREAT|O_EXCL|O_RDWR, 0600);
+		if (fd != -1)
+		{
+			close(fd);
+			return filename;
+		}
+		if (errno != EEXIST)
+			perror("could not create temporary file");
+		free(filename);
+	}
+}
diff --git a/modules/src/system/system.h b/modules/src/system/system.h
index 582dd44e9..5f596822e 100644
--- a/modules/src/system/system.h
+++ b/modules/src/system/system.h
@@ -78,11 +78,11 @@ time_t sys_modtime(char *);
  *
  * Supports both DOS and UNIX style paths.
  * */
-void sys_basename(const char *str, register char *dst);
+extern void sys_basename(const char *str, register char *dst);
 
-/* Creates a temporary filename. This has
- * the same semantics as ISO C90 tmpnam() */
-char* sys_tmpnam(char *buffer);
+/* Creates a temporary filename, makes it, and returns a malloc'd string
+ * containing the filename. */
+extern char* sys_maketempfile(const char* prefix, const char* suffix);
 
 #if defined WIN32
 /* Really? */
@@ -93,4 +93,8 @@ extern char* strndup(const char* s, size_t n);
  * sane systems. */
 extern void sys_setbinarymode(FILE* fp);
 
+/* As system sprintf(), except uses malloc() to allocate a new buffer of the
+ * right size for the result. */
+extern char* aprintf(const char* format, ...);
+
 #endif /* __SYSTEM_INCLUDED__ */
diff --git a/modules/src/system/tmpnam.c b/modules/src/system/tmpnam.c
deleted file mode 100644
index 1c58261ac..000000000
--- a/modules/src/system/tmpnam.c
+++ /dev/null
@@ -1,16 +0,0 @@
-/*  Copyright (c) 2019. See the file License in
- *  the root directory for more information.
- *
- *  Created on: 2019-03-13
- *  
- */
-#include <stdio.h>
-
-/* This has been placed here, because on some famous platforms, this
- * call is completely broken (e.g Windows up to recent versions of CRT)
- */
-char* sys_tmpnam(char *buffer)
-{
-	return tmpnam(buffer);
-}
-
diff --git a/util/LLgen/src/machdep.c b/util/LLgen/src/machdep.c
index f2d0bd9c1..602edcb61 100644
--- a/util/LLgen/src/machdep.c
+++ b/util/LLgen/src/machdep.c
@@ -18,10 +18,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #if defined WIN32
 #include <io.h>
-#else
-#include <unistd.h>
 #endif
 # include "extern.h"
 # include "types.h"
diff --git a/util/ack/files.c b/util/ack/files.c
index 04167e2e5..f72ff57ca 100644
--- a/util/ack/files.c
+++ b/util/ack/files.c
@@ -53,14 +53,11 @@ int setfiles(trf *phase) {
 		out.p_keeps=NO ;
 		out.p_keep=YES ;
 	} else {
-		gr_init(&pathname) ;
 		if ( !phase->t_keep && !t_flag ) {
-			gr_cat(&pathname, sys_gettmpdir());
-			gr_cat(&pathname, "/Ack-XXXXXX");
-			int fd = mkstemp(pathname.gr_string);
-			close(fd);
+			out.p_path = sys_maketempfile("ack", phase->t_out);
 			out.p_keep=NO ;
 		} else {
+			gr_init(&pathname) ;
 			if ( !p_basename ) {
 				gr_cat(&pathname,"Ack") ;
 				p_basename=keeps(gr_start(pathname)) ;
@@ -69,10 +66,10 @@ int setfiles(trf *phase) {
 			} else {
 				gr_cat(&pathname,p_basename) ;
 			}
+			gr_cat(&pathname,phase->t_out) ;
+			out.p_path= gr_final(&pathname) ;
 			out.p_keep=YES ;
 		}
-		gr_cat(&pathname,phase->t_out) ;
-		out.p_path= gr_final(&pathname) ;
 		out.p_keeps= YES ;
 	}
 	scanlist( l_first(arguments), elem) {
diff --git a/util/amisc/astrip.c b/util/amisc/astrip.c
index 669c76739..11ba03892 100644
--- a/util/amisc/astrip.c
+++ b/util/amisc/astrip.c
@@ -17,7 +17,7 @@
 
 */
 
-char	tname[L_tmpnam];
+char* tname;
 FILE	*tf;
 struct outhead buf;
 int	readerror, writeerror;
@@ -30,12 +30,7 @@ int main(int argc, char **argv)
 {
 	int	status;
 
-	if (sys_tmpnam(tname)==NULL)
-	{
-		fprintf(stderr, "astrip: cannot create temporary filename\n");
-		return(1);
-	}
-	fclose(fopen(tname,"wb"));
+	tname = sys_maketempfile("ack", "dat");
 	while(--argc) {
 		if ((status = strip(argv[argc])) > 1)
 			break;
diff --git a/util/arch/archiver.c b/util/arch/archiver.c
index 98fc79375..bc1b01557 100644
--- a/util/arch/archiver.c
+++ b/util/arch/archiver.c
@@ -120,8 +120,7 @@ char io_buffer[IO_SIZE];
 
 char *progname;
 
-char temp_buf[L_tmpnam];
-char *temp_arch = &temp_buf[0];
+char *temp_arch;
 
 void do_object(FILE* f, long size);
 void do_names(struct outhead *headp);
@@ -348,10 +347,7 @@ int main(int argc, char *argv[])
 		distr_time = statbuf.st_mtime;
 	}
 #endif
-	if (sys_tmpnam(temp_arch) == NULL)
-	{
-		error(TRUE, "Cannot create a temporary filename\n", NULL);
-	}
+	temp_arch = sys_maketempfile("aal", "dat");
 
 	if (app_fl + ex_fl + del_fl + rep_fl + show_fl + pr_fl != 1)
 		usage();
diff --git a/util/ass/ass80.c b/util/ass/ass80.c
index 21ca7cf76..168a4a2b6 100644
--- a/util/ass/ass80.c
+++ b/util/ass/ass80.c
@@ -17,7 +17,7 @@
  * this file contains several library routines.
  */
 
-static char filename[L_tmpnam];
+static char* filename;
 
 
 /* VARARGS1 */
@@ -384,9 +384,5 @@ void set_mode(int mode)
 
 char* tmpfil(void)
 {
-	if (sys_tmpnam(filename)==NULL)
-	{
-		fatal("Cannot create temporary filename.");
-	}
-	return filename;
+	return sys_maketempfile("ack-ass", "dat");
 }
diff --git a/util/ego/em_ego/em_ego.c b/util/ego/em_ego/em_ego.c
index 31364c298..1946966f2 100644
--- a/util/ego/em_ego/em_ego.c
+++ b/util/ego/em_ego/em_ego.c
@@ -59,7 +59,7 @@ static const struct
 #define MAXARGS 1024 /* mar # of args */
 #define NTEMPS 4 /* # of temporary files; not tunable */
 
-static char tmpbase[PATH_MAX];
+static char* tmpbase;
 static char ddump[PATH_MAX]; /* data label dump file */
 static char pdump[PATH_MAX]; /* procedure name dump file */
 static char tmpbufs[NTEMPS * 2][PATH_MAX];
@@ -389,11 +389,7 @@ int main(int argc, char* argv[])
 		fatal("no correct -P flag given");
 	}
 
-	{
-		strcpy(tmpbase, sys_gettmpdir());
-		strcat(tmpbase, "/ego.XXXXXX");
-		close(mkstemp(tmpbase));
-	}
+	tmpbase = sys_maketempfile("ego", "");
 
 	strcpy(ddump, tmpbase);
 	strcpy(pdump, tmpbase);
diff --git a/util/ego/il/il.c b/util/ego/il/il.c
index 478053ab6..34ff56c2f 100644
--- a/util/ego/il/il.c
+++ b/util/ego/il/il.c
@@ -38,12 +38,12 @@ calcnt_p cchead; /* call-count info of current proc */
 STATIC long space = 0;
 STATIC long total_size = 0;
 
-STATIC char cname[PATH_MAX];
-STATIC char ccname[PATH_MAX];
-STATIC char cname2[PATH_MAX];
+STATIC char* cname;
+STATIC char* ccname;
+STATIC char* cname2;
 
 /* For debugging only */
-STATIC char sname[PATH_MAX];
+STATIC char* sname;
 STATIC int kp_temps = 0;
 
 int Ssubst;
@@ -337,20 +337,11 @@ char* argv[];
 	go(argc, argv, no_action, no_action, no_action, il_flags);
 	il_extptab(fproc); /* add extended data structures */
 
-	strcpy(cname, tmpdir);
-	strcpy(ccname, tmpdir);
-	strcpy(sname, tmpdir);
-	strcpy(cname2, tmpdir);
+	cname = sys_maketempfile("il", "i1");
+	ccname = sys_maketempfile("il", "i2");
+	sname = sys_maketempfile("il", "i3");
+	cname2 = sys_maketempfile("il", "i4");
 
-	strcat(cname, "/ego.i1.XXXXXX");
-	strcat(ccname, "/ego.i2.XXXXXX");
-	strcat(sname, "/ego.i3.XXXXXX");
-	strcat(cname2, "/ego.i4.XXXXXX");
-
-	close(mkstemp(cname));
-	close(mkstemp(ccname));
-	close(mkstemp(sname));
-	close(mkstemp(cname2));
 	pass1(files->lname_in, files->bname_in, cname); /* grep calls, analyse procedures */
 	space = total_size * space / 100;
 	pass2(cname, space); /* select calls to be expanded */
diff --git a/util/opt/ext.h b/util/opt/ext.h
index 342ab17c0..d4609a43b 100644
--- a/util/opt/ext.h
+++ b/util/opt/ext.h
@@ -16,7 +16,7 @@ extern	bool	repl_longmuls;
 extern	byte	em_flag[];
 extern	line_p	instrs,pseudos;
 extern	FILE	*outfile;
-extern	char	tempname[];
+extern	char	*tempname;
 extern	offset	wordsize;
 extern	offset	pointersize;
 extern	char	*progname;
diff --git a/util/opt/main.c b/util/opt/main.c
index 10b9da0a8..415435f11 100644
--- a/util/opt/main.c
+++ b/util/opt/main.c
@@ -48,11 +48,7 @@ void fileinit(void)
 		error("wrong input file");
 	if (Lflag)
 	{
-
-		if (sys_tmpnam(tempname)==NULL)
-		{
-			error("can't create temporary file.");
-		}
+		tempname = sys_maketempfile("opt", "dat");
 		outfile = fopen(tempname, "wb");
 		if (outfile == NULL)
 			error("can't create %s", tempname);
diff --git a/util/opt/var.c b/util/opt/var.c
index 3e51a9a70..6085b5ba8 100644
--- a/util/opt/var.c
+++ b/util/opt/var.c
@@ -22,7 +22,7 @@ bool	repl_longmuls = 0;	/* replacing longmuls as well? */
 line_p	instrs,pseudos;		/* pointers to chains */
 sym_p	symhash[NSYMHASH];	/* array of pointers to chains */
 FILE	*outfile;
-char	tempname[L_tmpnam];
+char	*tempname;
 offset	wordsize = 0;
 offset	pointersize = 0;
 char	*progname;