From cbe2d68fd7c7c7bac692b3a2d200a5d2429ab201 Mon Sep 17 00:00:00 2001
From: simon <simon@cda61777-01e9-0310-a592-d414129be87e>
Date: Sun, 4 May 2003 14:18:18 +0000
Subject: [PATCH] Colin's const-fixing Patch Of Death. Seems to build fine on
 Windows as well as Unix, so it can go in.

git-svn-id: svn://svn.tartarus.org/sgt/putty@3162 cda61777-01e9-0310-a592-d414129be87e
---
 console.c      |  2 +-
 logging.c      |  2 +-
 mac/macevlog.c |  4 ++--
 mac/macnet.c   |  2 +-
 mac/macterm.c  |  4 ++--
 mac/mtcpnet.c  |  4 ++--
 mac/otnet.c    |  4 ++--
 network.h      |  6 +++---
 plink.c        |  2 +-
 portfwd.c      | 17 +++++++++--------
 proxy.c        |  8 ++++----
 proxy.h        |  2 +-
 psftp.c        |  2 +-
 putty.h        |  9 +++++----
 raw.c          | 10 +++++-----
 rlogin.c       | 11 ++++++-----
 scp.c          |  3 ++-
 ssh.c          | 27 +++++++++++++++------------
 ssh.h          | 15 ++++++++-------
 telnet.c       | 11 ++++++-----
 unix/gtkdlg.c  |  2 +-
 unix/pterm.c   |  5 +++--
 unix/pty.c     |  4 ++--
 unix/unix.h    |  2 +-
 unix/uxcons.c  |  2 +-
 unix/uxnet.c   | 16 ++++++++--------
 unix/uxplink.c |  2 +-
 windlg.c       |  2 +-
 window.c       |  2 +-
 winnet.c       |  6 +++---
 x11fwd.c       |  9 +++++----
 31 files changed, 104 insertions(+), 93 deletions(-)

diff --git a/console.c b/console.c
index 90b5fa4e..fe201347 100644
--- a/console.c
+++ b/console.c
@@ -270,7 +270,7 @@ void console_provide_logctx(void *logctx)
     console_logctx = logctx;
 }
 
-void logevent(void *frontend, char *string)
+void logevent(void *frontend, const char *string)
 {
     if (console_logctx)
 	log_eventlog(console_logctx, string);
diff --git a/logging.c b/logging.c
index d526474e..f32e9cae 100644
--- a/logging.c
+++ b/logging.c
@@ -43,7 +43,7 @@ void logtraffic(void *handle, unsigned char c, int logmode)
  * platforms. Platforms which don't have a meaningful stderr can
  * just avoid defining FLAG_STDERR.
  */
-void log_eventlog(void *handle, char *event)
+void log_eventlog(void *handle, const char *event)
 {
     struct LogContext *ctx = (struct LogContext *)handle;
     if ((flags & FLAG_STDERR) && (flags & FLAG_VERBOSE)) {
diff --git a/mac/macevlog.c b/mac/macevlog.c
index 5e3cf123..43a2658f 100644
--- a/mac/macevlog.c
+++ b/mac/macevlog.c
@@ -1,4 +1,4 @@
-/* $Id: macevlog.c,v 1.7 2003/04/12 21:06:34 ben Exp $ */
+/* $Id: macevlog.c,v 1.8 2003/05/04 14:18:18 simon Exp $ */
 /*
  * Copyright (c) 2003 Ben Harris
  * All rights reserved.
@@ -101,7 +101,7 @@ void mac_freeeventlog(Session *s)
     }
 }
 
-void logevent(void *frontend, char *str)
+void logevent(void *frontend, const char *str)
 {
     Session *s = frontend;
     ListBounds bounds, visible;
diff --git a/mac/macnet.c b/mac/macnet.c
index eb705e1a..106a6315 100644
--- a/mac/macnet.c
+++ b/mac/macnet.c
@@ -144,7 +144,7 @@ Socket sk_newlistener(char *srcaddr, int port, Plug plug, int local_host_only)
     return NULL;
 }
 
-char *sk_addr_error(SockAddr addr)
+const char *sk_addr_error(SockAddr addr)
 {
 
     if (stack != NULL)
diff --git a/mac/macterm.c b/mac/macterm.c
index c83cb6d8..88eb2668 100644
--- a/mac/macterm.c
+++ b/mac/macterm.c
@@ -1,4 +1,4 @@
-/* $Id: macterm.c,v 1.74 2003/04/12 21:07:25 ben Exp $ */
+/* $Id: macterm.c,v 1.75 2003/05/04 14:18:18 simon Exp $ */
 /*
  * Copyright (c) 1999 Simon Tatham
  * Copyright (c) 1999, 2002 Ben Harris
@@ -105,7 +105,7 @@ void post_paint(Session *s);
 
 void mac_startsession(Session *s)
 {
-    char *errmsg;
+    const char *errmsg;
     int i;
     WinInfo *wi;
 
diff --git a/mac/mtcpnet.c b/mac/mtcpnet.c
index 7644ddf5..5415fbc6 100644
--- a/mac/mtcpnet.c
+++ b/mac/mtcpnet.c
@@ -217,7 +217,7 @@ static int mactcp_write(Socket, char const *, int);
 static int mactcp_write_oob(Socket, char const*, int);
 static void mactcp_set_private_ptr(Socket, void *);
 static void *mactcp_get_private_ptr(Socket);
-static char *mactcp_socket_error(Socket);
+static const char *mactcp_socket_error(Socket);
 static void mactcp_set_frozen(Socket, int);
 
 static void mactcp_recv(Actual_Socket s, size_t len);
@@ -714,7 +714,7 @@ char *mactcp_addr_error(SockAddr addr)
     }
 }
 
-static char *mactcp_socket_error(Socket sock)
+static const char *mactcp_socket_error(Socket sock)
 {
     static char buf[64];
     Actual_Socket s = (Actual_Socket) sock;
diff --git a/mac/otnet.c b/mac/otnet.c
index 809906b3..970a78e5 100644
--- a/mac/otnet.c
+++ b/mac/otnet.c
@@ -185,7 +185,7 @@ static int ot_tcp_write_oob(Socket s, char const *data, int len);
 static void ot_tcp_set_private_ptr(Socket s, void *ptr);
 static void *ot_tcp_get_private_ptr(Socket s);
 static void ot_tcp_set_frozen(Socket s, int is_frozen);
-static char *ot_tcp_socket_error(Socket s);
+static const char *ot_tcp_socket_error(Socket s);
 static void ot_recv(Actual_Socket s);
 void ot_poll(void);
 
@@ -420,7 +420,7 @@ char *ot_addr_error(SockAddr addr)
     sprintf(buf, "error %d", addr->error);
     return buf;
 }
-static char *ot_tcp_socket_error(Socket sock)
+static const char *ot_tcp_socket_error(Socket sock)
 {
     Actual_Socket s = (Actual_Socket) sock;
     static char buf[128];
diff --git a/network.h b/network.h
index 657bdcb2..ad45547d 100644
--- a/network.h
+++ b/network.h
@@ -38,12 +38,12 @@ struct socket_function_table {
     void *(*get_private_ptr) (Socket s);
     void (*set_frozen) (Socket s, int is_frozen);
     /* ignored by tcp, but vital for ssl */
-    char *(*socket_error) (Socket s);
+    const char *(*socket_error) (Socket s);
 };
 
 struct plug_function_table {
     int (*closing)
-     (Plug p, char *error_msg, int error_code, int calling_back);
+     (Plug p, const char *error_msg, int error_code, int calling_back);
     /* error_msg is NULL iff it is not an error (ie it closed normally) */
     /* calling_back != 0 iff there is a Plug function */
     /* currently running (would cure the fixme in try_send()) */
@@ -130,7 +130,7 @@ Socket sk_register(void *sock, Plug plug);
  * if there's a problem. These functions extract an error message,
  * or return NULL if there's no problem.
  */
-char *sk_addr_error(SockAddr addr);
+const char *sk_addr_error(SockAddr addr);
 #define sk_socket_error(s) (((*s)->socket_error) (s))
 
 /*
diff --git a/plink.c b/plink.c
index 0f764cf3..bf17f530 100644
--- a/plink.c
+++ b/plink.c
@@ -558,7 +558,7 @@ int main(int argc, char **argv)
      */
     netevent = CreateEvent(NULL, FALSE, FALSE, NULL);
     {
-	char *error;
+	const char *error;
 	char *realhost;
 	/* nodelay is only useful if stdin is a character device (console) */
 	int nodelay = cfg.tcp_nodelay &&
diff --git a/portfwd.c b/portfwd.c
index e21ed3a2..f73d22cc 100644
--- a/portfwd.c
+++ b/portfwd.c
@@ -86,7 +86,7 @@ struct PFwdPrivate {
     int buflen;
 };
 
-static int pfd_closing(Plug plug, char *error_msg, int error_code,
+static int pfd_closing(Plug plug, const char *error_msg, int error_code,
 		       int calling_back)
 {
     struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
@@ -331,8 +331,8 @@ static void pfd_sent(Plug plug, int bufsize)
 /*
  * Called when receiving a PORT OPEN from the server
  */
-char *pfd_newconnect(Socket *s, char *hostname, int port, void *c,
-		     const Config *cfg)
+const char *pfd_newconnect(Socket *s, char *hostname, int port,
+			   void *c, const Config *cfg)
 {
     static const struct plug_function_table fn_table = {
 	pfd_closing,
@@ -342,7 +342,8 @@ char *pfd_newconnect(Socket *s, char *hostname, int port, void *c,
     };
 
     SockAddr addr;
-    char *err, *dummy_realhost;
+    const char *err;
+    char *dummy_realhost;
     struct PFwdPrivate *pr;
 
     /*
@@ -390,7 +391,7 @@ static int pfd_accepting(Plug p, void *sock)
     };
     struct PFwdPrivate *pr, *org;
     Socket s;
-    char *err;
+    const char *err;
 
     org = (struct PFwdPrivate *)p;
     pr = snew(struct PFwdPrivate);
@@ -437,8 +438,8 @@ static int pfd_accepting(Plug p, void *sock)
 /* Add a new forwarding from port -> desthost:destport
  sets up a listener on the local machine on (srcaddr:)port
  */
-char *pfd_addforward(char *desthost, int destport, char *srcaddr, int port,
-		     void *backhandle, const Config *cfg)
+const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
+			   int port, void *backhandle, const Config *cfg)
 {
     static const struct plug_function_table fn_table = {
 	pfd_closing,
@@ -447,7 +448,7 @@ char *pfd_addforward(char *desthost, int destport, char *srcaddr, int port,
 	pfd_accepting
     };
 
-    char *err;
+    const char *err;
     struct PFwdPrivate *pr;
     Socket s;
 
diff --git a/proxy.c b/proxy.c
index 2ea0bc8c..a15b3ba1 100644
--- a/proxy.c
+++ b/proxy.c
@@ -173,7 +173,7 @@ static void sk_proxy_set_frozen (Socket s, int is_frozen)
     sk_set_frozen(ps->sub_socket, is_frozen);
 }
 
-static char * sk_proxy_socket_error (Socket s)
+static const char * sk_proxy_socket_error (Socket s)
 {
     Proxy_Socket ps = (Proxy_Socket) s;
     if (ps->error != NULL || ps->sub_socket == NULL) {
@@ -184,7 +184,7 @@ static char * sk_proxy_socket_error (Socket s)
 
 /* basic proxy plug functions */
 
-static int plug_proxy_closing (Plug p, char *error_msg,
+static int plug_proxy_closing (Plug p, const char *error_msg,
 			       int error_code, int calling_back)
 {
     Proxy_Plug pp = (Proxy_Plug) p;
@@ -377,7 +377,7 @@ Socket new_connection(SockAddr addr, char *hostname,
 	Proxy_Socket ret;
 	Proxy_Plug pplug;
 	SockAddr proxy_addr;
-	char *proxy_canonical_name, *err;
+	char *proxy_canonical_name;
 
 	ret = snew(struct Socket_proxy_tag);
 	ret->fn = &socket_fn_table;
@@ -421,7 +421,7 @@ Socket new_connection(SockAddr addr, char *hostname,
 	/* look-up proxy */
 	proxy_addr = sk_namelookup(cfg->proxy_host,
 				   &proxy_canonical_name);
-	if ((err = sk_addr_error(proxy_addr)) != NULL) {
+	if (sk_addr_error(proxy_addr) != NULL) {
 	    ret->error = "Proxy error: Unable to resolve proxy host name";
 	    return (Socket)ret;
 	}
diff --git a/proxy.h b/proxy.h
index cc11061e..2bd52203 100644
--- a/proxy.h
+++ b/proxy.h
@@ -64,7 +64,7 @@ struct Socket_proxy_tag {
      */
 
     /* closing */
-    char *closing_error_msg;
+    const char *closing_error_msg;
     int closing_error_code;
     int closing_calling_back;
 
diff --git a/psftp.c b/psftp.c
index c93d7be3..75161519 100644
--- a/psftp.c
+++ b/psftp.c
@@ -1691,7 +1691,7 @@ static void usage(void)
 static int psftp_connect(char *userhost, char *user, int portnumber)
 {
     char *host, *realhost;
-    char *err;
+    const char *err;
 
     /* Separate host and username */
     host = userhost;
diff --git a/putty.h b/putty.h
index b243cbbc..93a10c72 100644
--- a/putty.h
+++ b/putty.h
@@ -266,8 +266,9 @@ enum {
 };
 
 struct backend_tag {
-    char *(*init) (void *frontend_handle, void **backend_handle, Config *cfg,
-		   char *host, int port, char **realhost, int nodelay);
+    const char *(*init) (void *frontend_handle, void **backend_handle,
+			 Config *cfg,
+			 char *host, int port, char **realhost, int nodelay);
     void (*free) (void *handle);
     /* back->reconfig() passes in a replacement configuration. */
     void (*reconfig) (void *handle, Config *cfg);
@@ -643,7 +644,7 @@ void log_reconfig(void *logctx, Config *cfg);
 void logfopen(void *logctx);
 void logfclose(void *logctx);
 void logtraffic(void *logctx, unsigned char c, int logmode);
-void log_eventlog(void *logctx, char *string);
+void log_eventlog(void *logctx, const char *string);
 enum { PKT_INCOMING, PKT_OUTGOING };
 void log_packet(void *logctx, int direction, int type,
 		char *texttype, void *data, int len);
@@ -778,7 +779,7 @@ int wc_unescape(char *output, const char *wildcard);
 /*
  * Exports from windlg.c
  */
-void logevent(void *frontend, char *);
+void logevent(void *frontend, const char *);
 void verify_ssh_host_key(void *frontend, char *host, int port, char *keytype,
 			 char *keystr, char *fingerprint);
 void askcipher(void *frontend, char *ciphername, int cs);
diff --git a/raw.c b/raw.c
index e7a159cd..c4936493 100644
--- a/raw.c
+++ b/raw.c
@@ -29,7 +29,7 @@ static void c_write(Raw raw, char *buf, int len)
     sk_set_frozen(raw->s, backlog > RAW_MAX_BACKLOG);
 }
 
-static int raw_closing(Plug plug, char *error_msg, int error_code,
+static int raw_closing(Plug plug, const char *error_msg, int error_code,
 		       int calling_back)
 {
     Raw raw = (Raw) plug;
@@ -67,9 +67,9 @@ static void raw_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *raw_init(void *frontend_handle, void **backend_handle,
-		      Config *cfg,
-		      char *host, int port, char **realhost, int nodelay)
+static const char *raw_init(void *frontend_handle, void **backend_handle,
+			    Config *cfg,
+			    char *host, int port, char **realhost, int nodelay)
 {
     static const struct plug_function_table fn_table = {
 	raw_closing,
@@ -77,7 +77,7 @@ static char *raw_init(void *frontend_handle, void **backend_handle,
 	raw_sent
     };
     SockAddr addr;
-    char *err;
+    const char *err;
     Raw raw;
 
     raw = snew(struct raw_backend_data);
diff --git a/rlogin.c b/rlogin.c
index aa8dc0dd..455c2d9d 100644
--- a/rlogin.c
+++ b/rlogin.c
@@ -32,7 +32,7 @@ static void c_write(Rlogin rlogin, char *buf, int len)
     sk_set_frozen(rlogin->s, backlog > RLOGIN_MAX_BACKLOG);
 }
 
-static int rlogin_closing(Plug plug, char *error_msg, int error_code,
+static int rlogin_closing(Plug plug, const char *error_msg, int error_code,
 			  int calling_back)
 {
     Rlogin rlogin = (Rlogin) plug;
@@ -97,9 +97,10 @@ static void rlogin_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *rlogin_init(void *frontend_handle, void **backend_handle,
-			 Config *cfg,
-			 char *host, int port, char **realhost, int nodelay)
+static const char *rlogin_init(void *frontend_handle, void **backend_handle,
+			       Config *cfg,
+			       char *host, int port, char **realhost,
+			       int nodelay)
 {
     static const struct plug_function_table fn_table = {
 	rlogin_closing,
@@ -107,7 +108,7 @@ static char *rlogin_init(void *frontend_handle, void **backend_handle,
 	rlogin_sent
     };
     SockAddr addr;
-    char *err;
+    const char *err;
     Rlogin rlogin;
 
     rlogin = snew(struct rlogin_tag);
diff --git a/scp.c b/scp.c
index 21fe3322..0c7fe74d 100644
--- a/scp.c
+++ b/scp.c
@@ -476,7 +476,8 @@ static void bump(char *fmt, ...)
  */
 static void do_cmd(char *host, char *user, char *cmd)
 {
-    char *err, *realhost;
+    const char *err;
+    char *realhost;
     DWORD namelen;
 
     if (host == NULL || host[0] == '\0')
diff --git a/ssh.c b/ssh.c
index 11683c0e..337cfa8b 100644
--- a/ssh.c
+++ b/ssh.c
@@ -662,7 +662,7 @@ struct ssh_tag {
 #define logevent(s) logevent(ssh->frontend, s)
 
 /* logevent, only printf-formatted. */
-static void logeventf(Ssh ssh, char *fmt, ...)
+static void logeventf(Ssh ssh, const char *fmt, ...)
 {
     va_list ap;
     char *buf;
@@ -2077,7 +2077,7 @@ static void ssh_do_close(Ssh ssh)
     }
 }
 
-static int ssh_closing(Plug plug, char *error_msg, int error_code,
+static int ssh_closing(Plug plug, const char *error_msg, int error_code,
 		       int calling_back)
 {
     Ssh ssh = (Ssh) plug;
@@ -2120,8 +2120,8 @@ static void ssh_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *connect_to_host(Ssh ssh, char *host, int port,
-			     char **realhost, int nodelay)
+static const char *connect_to_host(Ssh ssh, char *host, int port,
+				   char **realhost, int nodelay)
 {
     static const struct plug_function_table fn_table = {
 	ssh_closing,
@@ -2131,7 +2131,7 @@ static char *connect_to_host(Ssh ssh, char *host, int port,
     };
 
     SockAddr addr;
-    char *err;
+    const char *err;
 
     ssh->savedhost = snewn(1 + strlen(host), char);
     if (!ssh->savedhost)
@@ -3528,7 +3528,8 @@ static void ssh1_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 		struct ssh_rportfwd pf;
 		int hostsize, port;
 		char host[256], buf[1024];
-		char *p, *h, *e;
+		char *p, *h;
+		const char *e;
 		c = snew(struct ssh_channel);
 		c->ssh = ssh;
 
@@ -6000,8 +6001,10 @@ static void do_ssh2_authconn(Ssh ssh, unsigned char *in, int inlen, int ispkt)
 		    if (realpf == NULL) {
 			error = "Remote port is not recognised";
 		    } else {
-			char *e = pfd_newconnect(&c->u.pfd.s, realpf->dhost,
-						 realpf->dport, c, &ssh->cfg);
+			const char *e = pfd_newconnect(&c->u.pfd.s,
+						       realpf->dhost,
+						       realpf->dport, c,
+						       &ssh->cfg);
 			logeventf(ssh, "Received remote port open request"
 				  " for %s:%d", realpf->dhost, realpf->dport);
 			if (e != NULL) {
@@ -6110,11 +6113,11 @@ static void ssh2_protocol(Ssh ssh, unsigned char *in, int inlen, int ispkt)
  *
  * Returns an error message, or NULL on success.
  */
-static char *ssh_init(void *frontend_handle, void **backend_handle,
-		      Config *cfg,
-		      char *host, int port, char **realhost, int nodelay)
+static const char *ssh_init(void *frontend_handle, void **backend_handle,
+			    Config *cfg,
+			    char *host, int port, char **realhost, int nodelay)
 {
-    char *p;
+    const char *p;
     Ssh ssh;
 
     ssh = snew(struct ssh_tag);
diff --git a/ssh.h b/ssh.h
index e42bcc49..97600939 100644
--- a/ssh.h
+++ b/ssh.h
@@ -250,18 +250,19 @@ int random_byte(void);
 void random_add_noise(void *noise, int length);
 void random_add_heavynoise(void *noise, int length);
 
-void logevent(void *, char *);
+void logevent(void *, const char *);
 
 /* Allocate and register a new channel for port forwarding */
 void *new_sock_channel(void *handle, Socket s);
 void ssh_send_port_open(void *channel, char *hostname, int port, char *org);
 
 /* Exports from portfwd.c */
-extern char *pfd_newconnect(Socket * s, char *hostname, int port, void *c,
-			    const Config *cfg);
+extern const char *pfd_newconnect(Socket * s, char *hostname, int port,
+				  void *c, const Config *cfg);
 /* desthost == NULL indicates dynamic (SOCKS) port forwarding */
-extern char *pfd_addforward(char *desthost, int destport, char *srcaddr,
-			    int port, void *backhandle, const Config *cfg);
+extern const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
+				  int port, void *backhandle,
+				  const Config *cfg);
 extern void pfd_close(Socket s);
 extern int pfd_send(Socket s, char *data, int len);
 extern void pfd_confirm(Socket s);
@@ -269,8 +270,8 @@ extern void pfd_unthrottle(Socket s);
 extern void pfd_override_throttle(Socket s, int enable);
 
 /* Exports from x11fwd.c */
-extern char *x11_init(Socket *, char *, void *, void *, const char *, int,
-		      const Config *);
+extern const char *x11_init(Socket *, char *, void *, void *, const char *,
+			    int, const Config *);
 extern void x11_close(Socket);
 extern int x11_send(Socket, char *, int);
 extern void *x11_invent_auth(char *, int, char *, int, int);
diff --git a/telnet.c b/telnet.c
index d358f82f..f421cc58 100644
--- a/telnet.c
+++ b/telnet.c
@@ -631,7 +631,7 @@ static void do_telnet_read(Telnet telnet, char *buf, int len)
     }
 }
 
-static int telnet_closing(Plug plug, char *error_msg, int error_code,
+static int telnet_closing(Plug plug, const char *error_msg, int error_code,
 			  int calling_back)
 {
     Telnet telnet = (Telnet) plug;
@@ -671,9 +671,10 @@ static void telnet_sent(Plug plug, int bufsize)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *telnet_init(void *frontend_handle, void **backend_handle,
-			 Config *cfg,
-			 char *host, int port, char **realhost, int nodelay)
+static const char *telnet_init(void *frontend_handle, void **backend_handle,
+			       Config *cfg,
+			       char *host, int port, char **realhost,
+			       int nodelay)
 {
     static const struct plug_function_table fn_table = {
 	telnet_closing,
@@ -681,7 +682,7 @@ static char *telnet_init(void *frontend_handle, void **backend_handle,
 	telnet_sent
     };
     SockAddr addr;
-    char *err;
+    const char *err;
     Telnet telnet;
 
     telnet = snew(struct telnet_tag);
diff --git a/unix/gtkdlg.c b/unix/gtkdlg.c
index 1b58d141..a9383e75 100644
--- a/unix/gtkdlg.c
+++ b/unix/gtkdlg.c
@@ -2720,7 +2720,7 @@ void *eventlogstuff_new(void)
     return es;
 }
 
-void logevent_dlg(void *estuff, char *string)
+void logevent_dlg(void *estuff, const char *string)
 {
     struct eventlog_stuff *es = (struct eventlog_stuff *)estuff;
 
diff --git a/unix/pterm.c b/unix/pterm.c
index cf52ec38..751db8e7 100644
--- a/unix/pterm.c
+++ b/unix/pterm.c
@@ -166,7 +166,7 @@ int from_backend(void *frontend, int is_stderr, const char *data, int len)
     return term_data(inst->term, is_stderr, data, len);
 }
 
-void logevent(void *frontend, char *string)
+void logevent(void *frontend, const char *string)
 {
     struct gui_data *inst = (struct gui_data *)frontend;
 
@@ -3075,7 +3075,8 @@ int pt_main(int argc, char **argv)
 
     inst->back = select_backend(&inst->cfg);
     {
-	char *realhost, *error;
+	char *realhost;
+	const char *error;
 
 	error = inst->back->init((void *)inst, &inst->backhandle,
                                  &inst->cfg, inst->cfg.host, inst->cfg.port,
diff --git a/unix/pty.c b/unix/pty.c
index 5d856930..55282d2f 100644
--- a/unix/pty.c
+++ b/unix/pty.c
@@ -485,8 +485,8 @@ static void pty_uxsel_setup(void)
  * Also places the canonical host name into `realhost'. It must be
  * freed by the caller.
  */
-static char *pty_init(void *frontend, void **backend_handle, Config *cfg,
-		      char *host, int port, char **realhost, int nodelay)
+static const char *pty_init(void *frontend, void **backend_handle, Config *cfg,
+			    char *host, int port, char **realhost, int nodelay)
 {
     int slavefd;
     pid_t pid, pgrp;
diff --git a/unix/unix.h b/unix/unix.h
index aeffead4..28a026cb 100644
--- a/unix/unix.h
+++ b/unix/unix.h
@@ -64,7 +64,7 @@ void fatal_message_box(void *window, char *msg);
 void about_box(void *window);
 void *eventlogstuff_new(void);
 void showeventlog(void *estuff, void *parentwin);
-void logevent_dlg(void *estuff, char *string);
+void logevent_dlg(void *estuff, const char *string);
 int reallyclose(void *frontend);
 
 /* Things pterm.c needs from {ptermm,uxputty}.c */
diff --git a/unix/uxcons.c b/unix/uxcons.c
index 48770897..80ed246e 100644
--- a/unix/uxcons.c
+++ b/unix/uxcons.c
@@ -258,7 +258,7 @@ void old_keyfile_warning(void)
     fputs(message, stderr);
 }
 
-void logevent(void *frontend, char *string)
+void logevent(void *frontend, const char *string)
 {
     log_eventlog(logctx, string);
 }
diff --git a/unix/uxnet.c b/unix/uxnet.c
index 9d9e03bc..77a4885b 100644
--- a/unix/uxnet.c
+++ b/unix/uxnet.c
@@ -26,7 +26,7 @@
 struct Socket_tag {
     struct socket_function_table *fn;
     /* the above variable absolutely *must* be the first in this structure */
-    char *error;
+    const char *error;
     int s;
     Plug plug;
     void *private_ptr;
@@ -56,7 +56,7 @@ struct Socket_tag {
 typedef struct Socket_tag *Actual_Socket;
 
 struct SockAddr_tag {
-    char *error;
+    const char *error;
     /*
      * Which address family this address belongs to. AF_INET for
      * IPv4; AF_INET6 for IPv6; AF_UNSPEC indicates that name
@@ -115,7 +115,7 @@ void sk_cleanup(void)
     }
 }
 
-char *error_string(int error)
+const char *error_string(int error)
 {
     return strerror(error);
 }
@@ -322,7 +322,7 @@ static int sk_tcp_write_oob(Socket s, const char *data, int len);
 static void sk_tcp_set_private_ptr(Socket s, void *ptr);
 static void *sk_tcp_get_private_ptr(Socket s);
 static void sk_tcp_set_frozen(Socket s, int is_frozen);
-static char *sk_tcp_socket_error(Socket s);
+static const char *sk_tcp_socket_error(Socket s);
 
 static struct socket_function_table tcp_fn_table = {
     sk_tcp_plug,
@@ -837,8 +837,8 @@ static int net_select_result(int fd, int event)
 	    ret = recv(s->s, buf, sizeof(buf), MSG_OOB);
 	    noise_ultralight(ret);
 	    if (ret <= 0) {
-		char *str = (ret == 0 ? "Internal networking trouble" :
-			     error_string(errno));
+		const char *str = (ret == 0 ? "Internal networking trouble" :
+				   error_string(errno));
 		/* We're inside the Unix frontend here, so we know
 		 * that the frontend handle is unnecessary. */
 		logevent(NULL, str);
@@ -1003,11 +1003,11 @@ static void *sk_tcp_get_private_ptr(Socket sock)
  * if there's a problem. These functions extract an error message,
  * or return NULL if there's no problem.
  */
-char *sk_addr_error(SockAddr addr)
+const char *sk_addr_error(SockAddr addr)
 {
     return addr->error;
 }
-static char *sk_tcp_socket_error(Socket sock)
+static const char *sk_tcp_socket_error(Socket sock)
 {
     Actual_Socket s = (Actual_Socket) sock;
     return s->error;
diff --git a/unix/uxplink.c b/unix/uxplink.c
index 9fce0560..5d3efb29 100644
--- a/unix/uxplink.c
+++ b/unix/uxplink.c
@@ -574,7 +574,7 @@ int main(int argc, char **argv)
      */
     logctx = log_init(NULL, &cfg);
     {
-	char *error;
+	const char *error;
 	char *realhost;
 	/* nodelay is only useful if stdin is a terminal device */
 	int nodelay = cfg.tcp_nodelay && isatty(0);
diff --git a/windlg.c b/windlg.c
index a045dafa..c9f96fec 100644
--- a/windlg.c
+++ b/windlg.c
@@ -659,7 +659,7 @@ int do_reconfig(HWND hwnd)
     return ret;
 }
 
-void logevent(void *frontend, char *string)
+void logevent(void *frontend, const char *string)
 {
     char timebuf[40];
     time_t t;
diff --git a/window.c b/window.c
index 6d306f56..c9d8df55 100644
--- a/window.c
+++ b/window.c
@@ -636,7 +636,7 @@ int WINAPI WinMain(HINSTANCE inst, HINSTANCE prev, LPSTR cmdline, int show)
      * Start up the telnet connection.
      */
     {
-	char *error;
+	const char *error;
 	char msg[1024], *title;
 	char *realhost;
 
diff --git a/winnet.c b/winnet.c
index 6bb135c0..6052725b 100644
--- a/winnet.c
+++ b/winnet.c
@@ -465,7 +465,7 @@ static int sk_tcp_write_oob(Socket s, const char *data, int len);
 static void sk_tcp_set_private_ptr(Socket s, void *ptr);
 static void *sk_tcp_get_private_ptr(Socket s);
 static void sk_tcp_set_frozen(Socket s, int is_frozen);
-static char *sk_tcp_socket_error(Socket s);
+static const char *sk_tcp_socket_error(Socket s);
 
 extern char *do_select(SOCKET skt, int startup);
 
@@ -1173,11 +1173,11 @@ static void *sk_tcp_get_private_ptr(Socket sock)
  * if there's a problem. These functions extract an error message,
  * or return NULL if there's no problem.
  */
-char *sk_addr_error(SockAddr addr)
+const char *sk_addr_error(SockAddr addr)
 {
     return addr->error;
 }
-static char *sk_tcp_socket_error(Socket sock)
+static const char *sk_tcp_socket_error(Socket sock)
 {
     Actual_Socket s = (Actual_Socket) sock;
     return s->error;
diff --git a/x11fwd.c b/x11fwd.c
index 31931752..16944ee1 100644
--- a/x11fwd.c
+++ b/x11fwd.c
@@ -174,7 +174,7 @@ static char *x11_verify(unsigned long peer_ip, int peer_port,
     return NULL;
 }
 
-static int x11_closing(Plug plug, char *error_msg, int error_code,
+static int x11_closing(Plug plug, const char *error_msg, int error_code,
 		       int calling_back)
 {
     struct X11Private *pr = (struct X11Private *) plug;
@@ -232,8 +232,8 @@ int x11_get_screen_number(char *display)
  * Returns an error message, or NULL on success.
  * also, fills the SocketsStructure
  */
-char *x11_init(Socket * s, char *display, void *c, void *auth,
-	       const char *peeraddr, int peerport, const Config *cfg)
+const char *x11_init(Socket * s, char *display, void *c, void *auth,
+		     const char *peeraddr, int peerport, const Config *cfg)
 {
     static const struct plug_function_table fn_table = {
 	x11_closing,
@@ -244,7 +244,8 @@ char *x11_init(Socket * s, char *display, void *c, void *auth,
 
     SockAddr addr;
     int port;
-    char *err, *dummy_realhost;
+    const char *err;
+    char *dummy_realhost;
     char host[128];
     int n, displaynum;
     struct X11Private *pr;
-- 
2.11.0