rpcgen: Const correctness for C23

On some platforms, e.g. Linux Clang 22.1.8 / glibc 2.43, strchr()
now implements the C23 behaviour where passing a const pointer to
strchr() also returns a const pointer.  This breaks rpcgen during
the bootstrap build, since it assumes the return value is always
a mutable pointer.

For mkfile_output(), the pointed-to value is never modified, so
fix this by making the pointer const as well.

For open_log_file(), the current code modifies the supposedly const
value in-place to remove the filename suffix, which happens to work
but is wrong even in older versions of C.  Change the code to use a
printf "%.*s" format specifier to strip the suffix instead.

MFC after:	1 week
Reviewed by:	brooks
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D58489

2 files changed, 15 insertions, 7 deletions

diff --git a/usr.bin/rpcgen/rpc_main.c b/usr.bin/rpcgen/rpc_main.c
index 8d5afad86cff..4c69be1ed333 100644
--- a/usr.bin/rpcgen/rpc_main.c
+++ b/usr.bin/rpcgen/rpc_main.c
@@ -868,7 +868,8 @@ static void mkfile_output(struct commandline *cmd)
 {
 	const char *mkfilename, *clientname, *clntname, *xdrname, *hdrname;
 	const char *servername, *svcname, *servprogname, *clntprogname;
-	char *temp, *mkftemp;
+	const char *temp;
+	char *mkftemp;
 
 	svcname = file_name(cmd->infile, "_svc.c");
 	clntname = file_name(cmd->infile, "_clnt.c");
diff --git a/usr.bin/rpcgen/rpc_svcout.c b/usr.bin/rpcgen/rpc_svcout.c
index 2c6849714d75..bbeed976c2d2 100644
--- a/usr.bin/rpcgen/rpc_svcout.c
+++ b/usr.bin/rpcgen/rpc_svcout.c
@@ -31,6 +31,7 @@
  * rpc_svcout.c, Server-skeleton outputter for the RPC protocol compiler
  * Copyright (C) 1987, Sun Microsystems, Inc.
  */
+#include <limits.h>
 #include <stdio.h>
 #include <string.h>
 #include "rpc_parse.h"
@@ -931,14 +932,20 @@ write_rpc_svc_fg(const char *infile, const char *sp)
 static void
 open_log_file(const char *infile, const char *sp)
 {
-	char *s;
+	const char *s;
 
 	s = strrchr(infile, '.');
-	if (s)
-		*s = '\0';
-	f_print(fout, "%sopenlog(\"%s\", LOG_PID, LOG_DAEMON);\n", sp, infile);
-	if (s)
-		*s = '.';
+	if (s) {
+		size_t len;
+
+		len = s - infile;
+		if (len > INT_MAX)
+			len = INT_MAX;
+		f_print(fout, "%sopenlog(\"%.*s\", LOG_PID, LOG_DAEMON);\n",
+		    sp, (int)len, infile);
+	} else
+		f_print(fout, "%sopenlog(\"%s\", LOG_PID, LOG_DAEMON);\n",
+		    sp, infile);
 }