Fix glibc-2.43 constness warnings

Glibc 2.43 added C23 const-preserving overloads to various string functions,
which change the return type depending on the constness of the argument(s).
Currently this leads to warnings from calls to strtok() or strchr().
Fix this by properly declaring the respective variable types.

Signed-off-by: Holger Hoffstätte <holger@applied-asynchrony.com>

Author: hhoffstaette

access.c

@@ -99,7 +99,7 @@ static void make_mask(char *mask, int plen, int addrlen)
 	return;
 }
 
-static int match_address(const char *addr, const char *tok)
+static int match_address(const char *addr, char *tok)
 {
 	char *p;
 	struct addrinfo hints, *resa, *rest;

checksum.c

@@ -176,7 +176,7 @@ void parse_checksum_choice(int final_call)
 	if (valid_checksums.negotiated_nni)
 		xfer_sum_nni = file_sum_nni = valid_checksums.negotiated_nni;
 	else {
-		char *cp = checksum_choice ? strchr(checksum_choice, ',') : NULL;
+		const char *cp = checksum_choice ? strchr(checksum_choice, ',') : NULL;
 		if (cp) {
 			xfer_sum_nni = parse_csum_name(checksum_choice, cp - checksum_choice);
 			file_sum_nni = parse_csum_name(cp+1, -1);

compat.c

@@ -132,7 +132,7 @@ static const char *client_info;
  * of that protocol for it to be advertised as available. */
 static void check_sub_protocol(void)
 {
-	char *dot;
+	const char *dot;
 	int their_protocol, their_sub;
 	int our_sub = get_subprotocol_version();
 
@@ -415,7 +415,7 @@ static const char *getenv_nstr(int ntype)
 		env_str = ntype == NSTR_COMPRESS ? "zlib" : protocol_version >= 30 ? "md5" : "md4";
 
 	if (am_server && env_str) {
-		char *cp = strchr(env_str, '&');
+		const char *cp = strchr(env_str, '&');
 		if (cp)
 			env_str = cp + 1;
 	}

exclude.c

@@ -904,7 +904,7 @@ static int rule_matches(const char *fname, filter_rule *ex, int name_flags)
 {
 	int slash_handling, str_cnt = 0, anchored_match = 0;
 	int ret_match = ex->rflags & FILTRULE_NEGATE ? 0 : 1;
-	char *p, *pattern = ex->pattern;
+	const char *p, *pattern = ex->pattern;
 	const char *strings[16]; /* more than enough */
 	const char *name = fname + (*fname == '/');
 

io.c

@@ -1159,7 +1159,7 @@ void set_io_timeout(int secs)
 static void check_for_d_option_error(const char *msg)
 {
 	static const char rsync263_opts[] = "BCDHIKLPRSTWabceghlnopqrtuvxz";
-	char *colon;
+	const char *colon;
 	int saw_d = 0;
 
 	if (*msg != 'r'

loadparm.c

@@ -178,7 +178,7 @@ static char *expand_vars(const char *str)
 
 	for (t = buf, f = str; bufsize && *f; ) {
 		if (*f == '%' && isUpper(f+1)) {
-			char *percent = strchr(f+1, '%');
+			const char *percent = strchr(f+1, '%');
 			if (percent && percent - f < bufsize) {
 				char *val;
 				strlcpy(t, f+1, percent - f);