diff --git a/Makefile b/Makefile
index c188b89..982ca8d 100644
--- a/Makefile
+++ b/Makefile
@@ -39,3 +39,25 @@ util.o: util.c util.h
 rad50.o: rad50.c rad50.h
 dumpobj.o: dumpobj.c rad50.h util.h
 rad50.o: rad50.c rad50.h
+
+# Since the only tests we have so far are for crashes,
+# just try to assemble. Later, we will need expected/actual tests.
+
+# Test that all options requiring a value bail out if it's not present.
+argtests: macro11
+	@ for OPT in -e -d -m -p -o -l -ysl ; do \
+	  ./macro11 foo.mac $$OPT     2> /dev/null; \
+    if (( $$? == 1 )); then echo PASS; else echo FAIL; fi; \
+    echo "  $$OPT missing value"; \
+	  ./macro11 foo.mac $$OPT -v  2> /dev/null; \
+    if (( $$? == 1 )); then echo PASS; else echo FAIL; fi; \
+    echo "  $$OPT fol. by option"; \
+	done
+	@ ./macro11 foo.mac $$OPT -x -v 2> /dev/null; \
+    if (( $$? == 1 )); then echo PASS; else echo FAIL; fi; \
+    echo "  -x must be the last option"
+
+tests: macro11 argtests
+	@ ACTUAL=`./macro11 tests/test-undef.mac 2>&1`; \
+	if [ "tests/test-undef.mac:1: ***ERROR MACRO .TTYOU not found" == "$$ACTUAL" ]; then echo PASS; else echo FAIL; fi; \
+	echo "  test-undef.mac"
diff --git a/assemble.c b/assemble.c
index bb9cd42..67f0052 100644
--- a/assemble.c
+++ b/assemble.c
@@ -226,7 +226,7 @@ static int assemble(
                 if (!pass) {
                     /* This may work better in pass 2 - something in
                        RT-11 monitor needs the symbol to apear to be
-                       defined even if I can't resolve it's value. */
+                       defined even if I can't resolve its value. */
                     sym = add_sym(label, 0, SYMBOLFLAG_UNDEFINED, &absolute_section, &symbol_st);
                 } else
                     sym = NULL;
@@ -547,10 +547,12 @@ static int assemble(
                                 buffer_free(macbuf);
                             } else {
                                 strncpy(macfile, label, sizeof(macfile));
-                                strncat(macfile, ".MAC", sizeof(macfile) - strlen(macfile));
+                                strncat(macfile, ".MAC", sizeof(macfile) - strlen(macfile) - 1);
                                 my_searchenv(macfile, "MCALL", hitfile, sizeof(hitfile));
                                 if (hitfile[0])
                                     macstr = new_file_stream(hitfile);
+                                else
+                                    macstr = NULL;
                             }
 
                             if (macstr != NULL) {
diff --git a/assemble_aux.c b/assemble_aux.c
index 2457129..dc6b9d0 100644
--- a/assemble_aux.c
+++ b/assemble_aux.c
@@ -219,6 +219,7 @@ void implicit_gbl(
         break;
     case EX_LIT:
     case EX_SYM:
+    case EX_TEMP_SYM: // Impossible on this pass
         return;
     case EX_ADD:
     case EX_SUB:
diff --git a/dumpobj.c b/dumpobj.c
index 221fbe4..8399d6e 100644
--- a/dumpobj.c
+++ b/dumpobj.c
@@ -598,7 +598,7 @@ void got_isd(
     char *cp,
     int len)
 {
-    printf("ISD len=%o\n");
+    printf("ISD len=%o\n", len);
 }
 
 void got_endmod(
diff --git a/listing.c b/listing.c
index 0a88292..609494b 100644
--- a/listing.c
+++ b/listing.c
@@ -60,7 +60,7 @@ void list_source(
         if (!binline)
             binline = memcheck(malloc(sizeof(LSTFORMAT) + 16));
 
-        sprintf(binline, "%*s%*d", SIZEOF_MEMBER(LSTFORMAT, flag), "", SIZEOF_MEMBER(LSTFORMAT, line_number),
+        sprintf(binline, "%*s%*d", (int)SIZEOF_MEMBER(LSTFORMAT, flag), "", (int)SIZEOF_MEMBER(LSTFORMAT, line_number),
                 str->line);
     }
 }
@@ -87,21 +87,18 @@ static void list_fit(
     STREAM *str,
     unsigned addr)
 {
-    int             len = strlen(binline);
     size_t          col1 = offsetof(LSTFORMAT, source);
     size_t          col2 = offsetof(LSTFORMAT, pc);
 
     if (strlen(binline) >= col1) {
-        int             offset = offsetof(LSTFORMAT, pc);
-
         list_flush();
         listline[0] = 0;
         binline[0] = 0;
-        sprintf(binline, "%*s %6.6o", offsetof(LSTFORMAT, pc), "", addr);
+        sprintf(binline, "%*s %6.6o", (int)offsetof(LSTFORMAT, pc), "", addr);
         padto(binline, offsetof(LSTFORMAT, words));
     } else if (strlen(binline) <= col2) {
-        sprintf(binline, "%*s%*d %6.6o", SIZEOF_MEMBER(LSTFORMAT, flag), "",
-                SIZEOF_MEMBER(LSTFORMAT, line_number), str->line, addr);
+        sprintf(binline, "%*s%*d %6.6o", (int)SIZEOF_MEMBER(LSTFORMAT, flag), "",
+                (int)SIZEOF_MEMBER(LSTFORMAT, line_number), str->line, addr);
         padto(binline, offsetof(LSTFORMAT, words));
     }
 }
@@ -115,8 +112,8 @@ void list_value(
     if (dolist()) {
         /* Print the value and go */
         binline[0] = 0;
-        sprintf(binline, "%*s%*d %6.6o", SIZEOF_MEMBER(LSTFORMAT, flag), "",
-                SIZEOF_MEMBER(LSTFORMAT, line_number), str->line, word & 0177777);
+        sprintf(binline, "%*s%*d %6.6o", (int)SIZEOF_MEMBER(LSTFORMAT, flag), "",
+                (int)SIZEOF_MEMBER(LSTFORMAT, line_number), str->line, word & 0177777);
     }
 }
 
diff --git a/macro11.c b/macro11.c
index dca93f6..30bf8f7 100644
--- a/macro11.c
+++ b/macro11.c
@@ -108,7 +108,7 @@ static void print_help(
     printf("-e  enable <option> (see below)\n");
     printf("-h  print this help\n");
     printf("-l  gives the listing file name (.LST)\n");
-    printf("    -l without file name enables listing to stdout.\n");
+    printf("    -l - enables listing to stdout.\n");
     printf("-m  load RT-11 compatible macro library from which\n");
     printf("    .MCALLed macros can be found.\n");
     printf("    Multiple allowed.\n");
@@ -138,6 +138,10 @@ static void print_help(
     printf("\n");
 }
 
+void usage(char *message) {
+    fputs(message, stderr);
+    exit(EXIT_FAILURE);
+}
 
 int main(
     int argc,
@@ -146,9 +150,7 @@ int main(
     char           *fnames[32];
     int             nr_files = 0;
     FILE           *obj = NULL;
-    static char     line[1024];
     TEXT_RLD        tr;
-    char           *macname = NULL;
     char           *objname = NULL;
     char           *lstname = NULL;
     int             arg;
@@ -174,10 +176,16 @@ int main(
                 /* Followed by options to enable */
                 /* Since /SHOW and /ENABL option names don't overlap,
                    I consolidate. */
+                if(arg >= argc-1 || !isalpha(*argv[arg+1])) {
+                    usage("-e must be followed by an option to enable\n");
+                }
                 upcase(argv[++arg]);
                 enable_tf(argv[arg], 1);
             } else if (!stricmp(cp, "d")) {
                 /* Followed by an option to disable */
+                if(arg >= argc-1 || !isalpha(*argv[arg+1])) {
+                    usage("-d must be followed by an option to disable\n");
+                }
                 upcase(argv[++arg]);
                 enable_tf(argv[arg], 0);
             } else if (!stricmp(cp, "m")) {
@@ -185,6 +193,9 @@ int main(
                 /* This option gives the name of an RT-11 compatible
                    macro library from which .MCALLed macros can be
                    found. */
+                if(arg >= argc-1 || *argv[arg+1] == '-') {
+                    usage("-m must be followed by a macro library file name\n");
+                }
                 arg++;
                 mlbs[nr_mlbs] = mlb_open(argv[arg]);
                 if (mlbs[nr_mlbs] == NULL) {
@@ -199,6 +210,10 @@ int main(
                     char           *env = getenv("MCALL");
                     char           *temp;
 
+                    if(arg >= argc-1 || *argv[arg+1] == '-') {
+                        usage("-p must be followed by a macro search directory\n");
+                    }
+
                     if (env == NULL)
                         env = "";
 
@@ -212,11 +227,17 @@ int main(
                 }
             } else if (!stricmp(cp, "o")) {
                 /* The -o option gives the object file name (.OBJ) */
+                if(arg >= argc-1 || *argv[arg+1] == '-') {
+                    usage("-o must be followed by the object file name\n");
+                }
                 ++arg;
                 objname = argv[arg];
             } else if (!stricmp(cp, "l")) {
                 /* The option -l gives the listing file name (.LST) */
                 /* -l - enables listing to stdout. */
+                if(arg >= argc-1 || *argv[arg+1] == '-') {
+                    usage("-l must be followed by the listing file name (- for standard output)\n");
+                }
                 lstname = argv[++arg];
                 if (strcmp(lstname, "-") == 0)
                     lstfile = stdout;
@@ -230,25 +251,31 @@ int main(
                    must be the last command line option.  */
                 int             i;
 
+                if(arg != argc-1) {
+                    usage("-x must be the last option\n");
+                }
                 for (i = 0; i < nr_mlbs; i++)
                     mlb_extract(mlbs[i]);
                 return EXIT_SUCCESS;
             } else if (!stricmp(cp, "ysl")) {
                 /* set symbol_len */
-                char           *s = argv[++arg];
-                char           *endp;
-                int             sl = strtol(s, &endp, 10);
+                if (arg >= argc-1) {
+                    usage("-s must be followed by a number\n");
+                } else {
+                    char           *s = argv[++arg];
+                    char           *endp;
+                    int             sl = strtol(s, &endp, 10);
 
-                if (*endp || sl < SYMMAX_DEFAULT || sl > SYMMAX_MAX) {
-                    print_help();
-                    exit(EXIT_FAILURE);
+                    if (*endp || sl < SYMMAX_DEFAULT || sl > SYMMAX_MAX) {
+                        usage("-s must be followed by a number\n");
+                    }
+                    symbol_len = sl;
                 }
-                symbol_len = sl;
             } else if (!stricmp(cp, "yus")) {
                 /* allow underscores */
                 symbol_allow_underscores = 1;
             } else {
-                fprintf(stderr, "Unknown argument %s\n", argv[arg]);
+                fprintf(stderr, "Unknown option %s\n", argv[arg]);
                 print_help();
                 exit(EXIT_FAILURE);
             }
diff --git a/macros.c b/macros.c
index ee9779a..dd2af72 100644
--- a/macros.c
+++ b/macros.c
@@ -197,7 +197,8 @@ MACRO          *defmacro(
 
     while (!EOL(*cp)) {
         arg = new_arg();
-        if (arg->locsym = (*cp == '?')) /* special argument flag? */
+        arg->locsym = *cp == '?';
+        if (arg->locsym) /* special argument flag? */
             cp++;
         arg->label = get_symbol(cp, &cp, NULL);
         if (arg->label == NULL) {
@@ -335,8 +336,8 @@ BUFFER         *subst_args(
         if (issym(*in)) {
             label = get_symbol(in, &next, NULL);
             if (label) {
-                if (arg = find_arg(args, label)) {
-                    /* An apostrophy may appear before or after the symbol. */
+                if ((arg = find_arg(args, label))) {
+                    /* An apostrophe may appear before or after the symbol. */
                     /* In either case, remove it from the expansion. */
 
                     if (in > begin && in[-1] == '\'')
diff --git a/parse.c b/parse.c
index e990b10..c6c2f75 100644
--- a/parse.c
+++ b/parse.c
@@ -322,7 +322,7 @@ int parse_float(
         }
     }
 
-    flt[0] = (unsigned) (sign | (exp << 7) | (ufrac >> 48) & 0x7F);
+    flt[0] = (unsigned) (sign | (exp << 7) | ((ufrac >> 48) & 0x7F));
     if (size > 1) {
         flt[1] = (unsigned) ((ufrac >> 32) & 0xffff);
         if (size > 2) {
@@ -509,7 +509,7 @@ char           *get_symbol(
             if (symcp[len - 1] == '$') {
                 char           *newsym = memcheck(malloc(32));  /* Overkill */
 
-                sprintf(newsym, "%d$%d", strtol(symcp, NULL, 10), lsb);
+                sprintf(newsym, "%ld$%d", strtol(symcp, NULL, 10), lsb);
                 free(symcp);
                 symcp = newsym;
                 if (islocal)
diff --git a/tests/test-undef.mac b/tests/test-undef.mac
new file mode 100644
index 0000000..e9a4a1f
--- /dev/null
+++ b/tests/test-undef.mac
@@ -0,0 +1 @@
+        .MCALL  .TTYOUT