diff --color -ru a/libcap/_makenames.c b/libcap/_makenames.c

--- a/libcap/_makenames.c	2022-01-28 14:41:38.357147972 +0100

+++ b/libcap/_makenames.c	2022-01-28 14:42:45.681379827 +0100

@@ -45,7 +45,7 @@

 	if (maxcaps <= list[i].index) {

 	    maxcaps = list[i].index + 1;

 	}

-        if (list[i].index >= pointers_avail) {

+        if (pointers == NULL || list[i].index >= pointers_avail) {

 	    int was = pointers_avail * sizeof(char *);

 	    pointers_avail = 2 * list[i].index + 1;

 	    pointers = recalloc(pointers, was, pointers_avail * sizeof(char *));

diff --color -ru a/progs/capsh.c b/progs/capsh.c

--- a/progs/capsh.c	2022-01-28 14:41:38.359148009 +0100

+++ b/progs/capsh.c	2022-01-28 14:42:45.682379846 +0100

@@ -34,6 +34,35 @@

 #define MAX_GROUPS       100   /* max number of supplementary groups for user */

+/* parse a non-negative integer with some error handling */

+static unsigned long nonneg_uint(const char *text, const char *prefix, int *ok)

+{

+    char *remains;

+    unsigned long value;

+    ssize_t len = strlen(text);

+

+    if (len == 0 || *text == '-') {

+	goto fail;

+    }

+    value = strtoul(text, &remains, 0);

+    if (*remains) {

+	goto fail;

+    }

+    if (ok != NULL) {

+	*ok = 1;

+    }

+    return value;

+

+fail:

+    if (ok == NULL) {

+	fprintf(stderr, "%s: want non-negative integer, got \"%s\"\n",

+		prefix, text);

+	exit(1);

+    }

+    *ok = 0;

+    return 0;

+}

+

 static char *binary(unsigned long value)

 {

     static char string[8*sizeof(unsigned long) + 1];

@@ -362,7 +391,7 @@

     parts = strdup(path);

     if (parts == NULL) {

-        fprintf(stderr, "insufficient memory for parts of path\n");

+	fprintf(stderr, "insufficient memory for parts of path\n");

 	exit(1);

     }

@@ -610,7 +639,7 @@

 	    unsigned value;

 	    int set;

-	    value = strtoul(argv[i]+7, NULL, 0);

+	    value = nonneg_uint(argv[i]+7, "invalid --keep value", NULL);

 	    set = prctl(PR_SET_KEEPCAPS, value);

 	    if (set < 0) {

 		fprintf(stderr, "prctl(PR_SET_KEEPCAPS, %u) failed: %s\n",

@@ -667,7 +696,7 @@

 	} else if (!strncmp("--secbits=", argv[i], 10)) {

 	    unsigned value;

 	    int status;

-	    value = strtoul(argv[i]+10, NULL, 0);

+	    value = nonneg_uint(argv[i]+10, "invalid --secbits value", NULL);

 	    status = cap_set_secbits(value);

 	    if (status < 0) {

 		fprintf(stderr, "failed to set securebits to 0%o/0x%x\n",

@@ -680,7 +709,7 @@

 		fprintf(stderr, "already forked\n");

 		exit(1);

 	    }

-	    value = strtoul(argv[i]+10, NULL, 0);

+	    value = nonneg_uint(argv[i]+10, "invalid --forkfor value", NULL);

 	    if (value == 0) {

 		goto usage;

 	    }

@@ -696,7 +725,8 @@

 	    pid_t result;

 	    unsigned value;

-	    value = strtoul(argv[i]+9, NULL, 0);

+	    value = nonneg_uint(argv[i]+9, "invalid --killit signo value",

+				NULL);

 	    if (!child) {

 		fprintf(stderr, "no forked process to kill\n");

 		exit(1);

@@ -722,7 +752,7 @@

 	    unsigned value;

 	    int status;

-	    value = strtoul(argv[i]+6, NULL, 0);

+	    value = nonneg_uint(argv[i]+6, "invalid --uid value", NULL);

 	    status = setuid(value);

 	    if (status < 0) {

 		fprintf(stderr, "Failed to set uid=%u: %s\n",

@@ -733,7 +763,7 @@

 	    unsigned value;

 	    int status;

-	    value = strtoul(argv[i]+10, NULL, 0);

+	    value = nonneg_uint(argv[i]+10, "invalid --cap-uid value", NULL);

 	    status = cap_setuid(value);

 	    if (status < 0) {

 		fprintf(stderr, "Failed to cap_setuid(%u): %s\n",

@@ -744,7 +774,7 @@

 	    unsigned value;

 	    int status;

-	    value = strtoul(argv[i]+6, NULL, 0);

+	    value = nonneg_uint(argv[i]+6, "invalid --gid value", NULL);

 	    status = setgid(value);

 	    if (status < 0) {

 		fprintf(stderr, "Failed to set gid=%u: %s\n",

@@ -924,7 +954,7 @@

 	} else if (!strncmp("--is-uid=", argv[i], 9)) {

 	    unsigned value;

 	    uid_t uid;

-	    value = strtoul(argv[i]+9, NULL, 0);

+	    value = nonneg_uint(argv[i]+9, "invalid --is-uid value", NULL);

 	    uid = getuid();

 	    if (uid != value) {

 		fprintf(stderr, "uid: got=%d, want=%d\n", uid, value);

@@ -933,7 +963,7 @@

 	} else if (!strncmp("--is-gid=", argv[i], 9)) {

 	    unsigned value;

 	    gid_t gid;

-	    value = strtoul(argv[i]+9, NULL, 0);

+	    value = nonneg_uint(argv[i]+9, "invalid --is-gid value", NULL);

 	    gid = getgid();

 	    if (gid != value) {

 		fprintf(stderr, "gid: got=%d, want=%d\n", gid, value);

diff --color -ru a/tests/libcap_psx_test.c b/tests/libcap_psx_test.c

--- a/tests/libcap_psx_test.c	2022-01-28 14:41:38.360148027 +0100

+++ b/tests/libcap_psx_test.c	2022-01-28 14:42:45.683379864 +0100

@@ -21,7 +21,10 @@

 	exit(1);

     }

     if (pid == 0) {

-	cap_set_proc(start);

+	if (cap_set_proc(start)) {

+	    perror("setting empty caps failed");

+	    exit(1);

+	}

 	exit(0);

     }

     int res;

@@ -51,7 +54,10 @@

     for (i = 0; i < 10; i++) {

 	printf(".");     /* because of fork, this may print double */

 	fflush(stdout);  /* try to limit the above effect */

-	cap_set_proc(start);

+	if (cap_set_proc(start)) {

+	    perror("failed to set proc");

+	    exit(1);

+	}

 	usleep(1000);

     }

     printf(" PASSED\n");