diff --git a/gdbstub.c b/gdbstub.c
index d54abd17cc..b129df4e59 100644
--- a/gdbstub.c
+++ b/gdbstub.c
@@ -1987,7 +1987,7 @@ void gdb_do_syscall(gdb_syscall_complete_cb cb, const char *fmt, ...)
     va_end(va);
 }
 
-static void gdb_read_byte(GDBState *s, int ch)
+static void gdb_read_byte(GDBState *s, uint8_t ch)
 {
     uint8_t reply;
 
@@ -2001,7 +2001,7 @@ static void gdb_read_byte(GDBState *s, int ch)
         } else if (ch == '+') {
             trace_gdbstub_io_got_ack();
         } else {
-            trace_gdbstub_io_got_unexpected((uint8_t)ch);
+            trace_gdbstub_io_got_unexpected(ch);
         }
 
         if (ch == '+' || ch == '$')
@@ -2024,7 +2024,7 @@ static void gdb_read_byte(GDBState *s, int ch)
                 s->line_sum = 0;
                 s->state = RS_GETLINE;
             } else {
-                trace_gdbstub_err_garbage((uint8_t)ch);
+                trace_gdbstub_err_garbage(ch);
             }
             break;
         case RS_GETLINE:
@@ -2064,13 +2064,17 @@ static void gdb_read_byte(GDBState *s, int ch)
             }
             break;
         case RS_GETLINE_RLE:
-            if (ch < ' ') {
+            /*
+             * Run-length encoding is explained in "Debugging with GDB /
+             * Appendix E GDB Remote Serial Protocol / Overview".
+             */
+            if (ch < ' ' || ch == '#' || ch == '$' || ch > 126) {
                 /* invalid RLE count encoding */
-                trace_gdbstub_err_invalid_repeat((uint8_t)ch);
+                trace_gdbstub_err_invalid_repeat(ch);
                 s->state = RS_GETLINE;
             } else {
                 /* decode repeat length */
-                int repeat = (unsigned char)ch - ' ' + 3;
+                int repeat = ch - ' ' + 3;
                 if (s->line_buf_index + repeat >= sizeof(s->line_buf) - 1) {
                     /* that many repeats would overrun the command buffer */
                     trace_gdbstub_err_overrun();
@@ -2092,7 +2096,7 @@ static void gdb_read_byte(GDBState *s, int ch)
         case RS_CHKSUM1:
             /* get high hex digit of checksum */
             if (!isxdigit(ch)) {
-                trace_gdbstub_err_checksum_invalid((uint8_t)ch);
+                trace_gdbstub_err_checksum_invalid(ch);
                 s->state = RS_GETLINE;
                 break;
             }
@@ -2103,7 +2107,7 @@ static void gdb_read_byte(GDBState *s, int ch)
         case RS_CHKSUM2:
             /* get low hex digit of checksum */
             if (!isxdigit(ch)) {
-                trace_gdbstub_err_checksum_invalid((uint8_t)ch);
+                trace_gdbstub_err_checksum_invalid(ch);
                 s->state = RS_GETLINE;
                 break;
             }
diff --git a/qemu-bridge-helper.c b/qemu-bridge-helper.c
index 5396fbfbb6..f9940deefd 100644
--- a/qemu-bridge-helper.c
+++ b/qemu-bridge-helper.c
@@ -75,7 +75,7 @@ static int parse_acl_file(const char *filename, ACLList *acl_list)
         char *ptr = line;
         char *cmd, *arg, *argend;
 
-        while (isspace(*ptr)) {
+        while (g_ascii_isspace(*ptr)) {
             ptr++;
         }
 
@@ -99,12 +99,12 @@ static int parse_acl_file(const char *filename, ACLList *acl_list)
 
         *arg = 0;
         arg++;
-        while (isspace(*arg)) {
+        while (g_ascii_isspace(*arg)) {
             arg++;
         }
 
         argend = arg + strlen(arg);
-        while (arg != argend && isspace(*(argend - 1))) {
+        while (arg != argend && g_ascii_isspace(*(argend - 1))) {
             argend--;
         }
         *argend = 0;
diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
index 0033b61f2e..5b771de7a3 100644
--- a/tests/vhost-user-bridge.c
+++ b/tests/vhost-user-bridge.c
@@ -30,6 +30,7 @@
 #define _FILE_OFFSET_BITS 64
 
 #include "qemu/osdep.h"
+#include "qemu-common.h"
 #include "qemu/atomic.h"
 #include "qemu/iov.h"
 #include "standard-headers/linux/virtio_net.h"
@@ -645,7 +646,7 @@ vubr_host_notifier_setup(VubrDev *dev)
 static void
 vubr_set_host(struct sockaddr_in *saddr, const char *host)
 {
-    if (isdigit(host[0])) {
+    if (qemu_isdigit(host[0])) {
         if (!inet_aton(host, &saddr->sin_addr)) {
             fprintf(stderr, "inet_aton() failed.\n");
             exit(1);
diff --git a/util/cutils.c b/util/cutils.c
index d682c90901..9aacc422ca 100644
--- a/util/cutils.c
+++ b/util/cutils.c
@@ -683,7 +683,7 @@ int parse_uint(const char *s, unsigned long long *value, char **endptr,
     }
 
     /* make sure we reject negative numbers: */
-    while (isspace((unsigned char)*s)) {
+    while (qemu_isspace(*s)) {
         s++;
     }
     if (*s == '-') {