diff --git a/include/extern.h b/include/extern.h
index f03e0e0f5..ac5ec9dd2 100644
--- a/include/extern.h
+++ b/include/extern.h
@@ -1127,36 +1127,39 @@ extern boolean digit(char);
 extern boolean letter(char);
 extern char highc(char);
 extern char lowc(char);
-extern char *lcase(char *) NONNULLARG1;
-extern char *ucase(char *) NONNULLARG1;
-extern char *upstart(char *);
-extern char *upwords(char *) NONNULLARG1;
-extern char *mungspaces(char *) NONNULLARG1;
-extern char *trimspaces(char *) NONNULLARG1;
-extern char *strip_newline(char *) NONNULLARG1;
-extern char *stripchars(char *, const char *, const char *) NONNULLPTRS;
-extern char *stripdigits(char *) NONNULLARG1;
-extern char *eos(char *) NONNULLARG1;
-extern const char *c_eos(const char *) NONNULLARG1;
+extern char *lcase(char *) NONNULL NONNULLARG1;
+extern char *ucase(char *) NONNULL NONNULLARG1;
+extern char *upstart(char *); /* ought to be changed to NONNULL NONNULLARG1
+                               * and the code changed to not allow NULL arg */
+extern char *upwords(char *) NONNULL NONNULLARG1;
+extern char *mungspaces(char *) NONNULL NONNULLARG1;
+extern char *trimspaces(char *) NONNULL NONNULLARG1;
+extern char *strip_newline(char *) NONNULL NONNULLARG1;
+extern char *eos(char *) NONNULL NONNULLARG1;
+extern const char *c_eos(const char *) NONNULL NONNULLARG1;
 extern unsigned Strlen_(const char *, const char *, int) NONNULLPTRS;
 extern boolean str_start_is(const char *, const char *, boolean) NONNULLPTRS;
 extern boolean str_end_is(const char *, const char *) NONNULLPTRS;
 extern int str_lines_maxlen(const char *);
-extern char *strkitten(char *, char) NONNULLARG1;
+extern char *strkitten(char *, char) NONNULL NONNULLARG1;
 extern void copynchars(char *, const char *, int) NONNULLARG12;
 extern char chrcasecpy(int, int);
-extern char *strcasecpy(char *, const char *) NONNULLPTRS;
-extern char *s_suffix(const char *) NONNULLARG1;
-extern char *ing_suffix(const char *) NONNULLARG1;
-extern char *xcrypt(const char *, char *) NONNULLPTRS;
+extern char *strcasecpy(char *, const char *) NONNULL NONNULLPTRS;
+extern char *s_suffix(const char *) NONNULL NONNULLARG1;
+extern char *ing_suffix(const char *) NONNULL NONNULLARG1;
+extern char *xcrypt(const char *, char *) NONNULL NONNULLPTRS;
 extern boolean onlyspace(const char *) NONNULLARG1;
-extern char *tabexpand(char *) NONNULLARG1;
-extern char *visctrl(char);
-extern char *strsubst(char *, const char *, const char *);
+extern char *tabexpand(char *) NONNULL NONNULLARG1;
+extern char *visctrl(char) NONNULL;
+extern char *stripchars(char *, const char *,
+                                            const char *) NONNULL NONNULLPTRS;
+extern char *stripdigits(char *) NONNULL NONNULLARG1;
+extern char *strsubst(char *, const char *, const char *) NONNULL NONNULLPTRS;
 extern int strNsubst(char *, const char *, const char *, int) NONNULLPTRS;
-extern const char *findword(const char *, const char *, int, boolean);
-extern const char *ordin(int);
-extern char *sitoa(int);
+extern const char *findword(const char *, const char *, int,
+                                                         boolean) NONNULLARG2;
+extern const char *ordin(int) NONNULL;
+extern char *sitoa(int) NONNULL;
 extern int sgn(int);
 extern int rounddiv(long, int);
 extern int dist2(coordxy, coordxy, coordxy, coordxy);
@@ -1181,11 +1184,11 @@ extern void reseed_random(int(*fn)(int));
 extern time_t getnow(void);
 extern int getyear(void);
 #if 0
-extern char *yymmdd(time_t);
+extern char *yymmdd(time_t) NONNULL;
 #endif
 extern long yyyymmdd(time_t);
 extern long hhmmss(time_t);
-extern char *yyyymmddhhmmss(time_t);
+extern char *yyyymmddhhmmss(time_t) NONNULL;
 extern time_t time_from_yyyymmddhhmmss(char *);
 extern int phase_of_the_moon(void);
 extern boolean friday_13th(void);
diff --git a/src/files.c b/src/files.c
index e64d9f3a5..9a8c35f2f 100644
--- a/src/files.c
+++ b/src/files.c
@@ -3460,7 +3460,7 @@ config_erradd(const char *buf)
 
     /* if buf[] doesn't end in a period, exclamation point, or question mark,
        we'll include a period (in the message, not appended to buf[]) */
-    punct = eos((char *) buf) - 1; /* eos(buf)-1 is valid; cast away const */
+    punct = c_eos((char *) buf) - 1; /* eos(buf)-1 is valid */
     punct = strchr(".!?", *punct) ? "" : ".";
 
     if (!gp.program_state.config_error_ready) {
diff --git a/src/hacklib.c b/src/hacklib.c
index 055628fc1..f8a5a475d 100644
--- a/src/hacklib.c
+++ b/src/hacklib.c
@@ -224,6 +224,7 @@ eos(char *s)
     return s;
 }
 
+/* version of eos() which takes a const* arg and returns that result */
 const char *
 c_eos(const char *s)
 {
@@ -519,22 +520,23 @@ visctrl(char c)
 /* caller is responsible for ensuring that bp is a
    valid pointer to a BUFSZ buffer */
 char *
-stripchars(char *bp, const char *stuff_to_strip, const char *orig)
+stripchars(
+    char *bp,
+    const char *stuff_to_strip,
+    const char *orig)
 {
     int i = 0;
     char *s = bp;
 
-    if (s) {
-        while (*orig && i < (BUFSZ - 1)) {
-            if (!strchr(stuff_to_strip, *orig)) {
-                *s++ = *orig;
-                i++;
-            }
-            orig++;
+    while (*orig && i < (BUFSZ - 1)) {
+        if (!strchr(stuff_to_strip, *orig)) {
+            *s++ = *orig;
+            i++;
         }
-        *s = '\0';
-    } else
-        impossible("no output buf in stripchars");
+        orig++;
+    }
+    *s = '\0';
+
     return bp;
 }
 
@@ -552,21 +554,22 @@ stripdigits(char *s)
     return s;
 }
 
-/* substitute a word or phrase in a string (in place) */
-/* caller is responsible for ensuring that bp points to big enough buffer */
+/* substitute a word or phrase in a string (in place);
+   caller is responsible for ensuring that bp points to big enough buffer */
 char *
-strsubst(char *bp, const char *orig, const char *replacement)
+strsubst(
+    char *bp,
+    const char *orig,
+    const char *replacement)
 {
     char *found, buf[BUFSZ];
+    /* [this could be replaced by strNsubst(bp, orig, replacement, 1)] */
 
-    if (bp) {
-        /* [this could be replaced by strNsubst(bp, orig, replacement, 1)] */
-        found = strstr(bp, orig);
-        if (found) {
-            Strcpy(buf, found + strlen(orig));
-            Strcpy(found, replacement);
-            Strcat(bp, buf);
-        }
+    found = strstr(bp, orig);
+    if (found) {
+        Strcpy(buf, found + strlen(orig));
+        Strcpy(found, replacement);
+        Strcat(bp, buf);
     }
     return bp;
 }
@@ -828,8 +831,9 @@ pmatchz(const char *patrn, const char *strng)
 /* case insensitive counted string comparison */
 /*{ aka strncasecmp }*/
 int
-strncmpi(const char *s1, const char *s2,
-         int n) /*(should probably be size_t, which is unsigned)*/
+strncmpi(
+    const char *s1, const char *s2,
+    int n) /*(should probably be size_t, which is unsigned)*/
 {
     char t1, t2;
 
@@ -895,8 +899,10 @@ strstri(const char *str, const char *sub)
 /* compare two strings for equality, ignoring the presence of specified
    characters (typically whitespace) and possibly ignoring case */
 boolean
-fuzzymatch(const char *s1, const char *s2, const char *ignore_chars,
-           boolean caseblind)
+fuzzymatch(
+    const char *s1, const char *s2,
+    const char *ignore_chars,
+    boolean caseblind)
 {
     char c1, c2;
 
@@ -1158,13 +1164,13 @@ time_from_yyyymmddhhmmss(char *buf)
             t.tm_sec = atoi(s);
             timeresult = mktime(&t);
         }
-        if (timeresult == (time_t) -1)
+        if (timeresult == (time_t) -1) {
             debugpline1("time_from_yyyymmddhhmmss(%s) would have returned -1",
                         buf ? buf : "");
-        else
-            return timeresult;
+            timeresult = (time_t) 0;
+        }
     }
-    return (time_t) 0;
+    return timeresult;
 }
 
 /*