From 04f99c49513427cf8b61a3b5551b4e36a78ccd45 Mon Sep 17 00:00:00 2001
From: Andrew Wood <andrew.wood@ivarch.com>
Date: Thu, 19 Mar 2026 22:57:41 +0000
Subject: [PATCH] Use a special type for opts->argv[] so that the whole array,
 and array entries, can both be NULL, and the array entries pointers to
 constant strings; and ensure that argv[] always has a NULL pointer on the end
 - all so argv can be passed to execvp() (#67).

---
 src/include/options.h | 4 +++-
 src/main/options.c    | 6 ++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/src/include/options.h b/src/include/options.h
index bf07871..ecf0b23 100644
--- a/src/include/options.h
+++ b/src/include/options.h
@@ -46,6 +46,8 @@ typedef enum {
 	PV_SIDE_BOTH			/* monitor both sides */
 } pvside_t;
 
+typedef /*@null@*/ const char * argv_string;
+
 /*
  * Structure describing run-time options.
  *
@@ -66,7 +68,7 @@ struct opts_s {
 	/*@keep@*/ /*@null@*/ char *extra_display; /* extra display specifier, if any */
 	/*@keep@*/ /*@null@*/ pid_t *watchfd_pid;  /* array of processes to watch fds of */
 	/*@keep@*/ /*@null@*/ int *watchfd_fd;  /* array of fds to watch in each one (0=all) */
-	/*@keep@*/ /*@null@*/ const char **argv;   /* array of non-option arguments */
+	/*@keep@*/ /*@null@*/ argv_string *argv;   /* array of non-option arguments */
 	size_t lastwritten;            /* show N bytes last written */
 	off_t rate_limit;              /* rate limit, in bytes per second */
 	size_t buffer_size;            /* buffer size, in bytes (0=default) */
diff --git a/src/main/options.c b/src/main/options.c
index c6e691c..879f3e3 100644
--- a/src/main/options.c
+++ b/src/main/options.c
@@ -92,12 +92,13 @@ void opts_free( /*@only@ */ opts_t opts)
 
 /*
  * Add a filename to the list of non-option arguments, returning false on
- * error.  The filename is not copied - the pointer is stored.
+ * error.  The filename is not copied - the pointer is stored.  The list is
+ * guaranteed to have a NULL after the last item.
  */
 bool opts_add_file(opts_t opts, const char *filename)
 {
 	/*@-branchstate@ */
-	if ((opts->argc >= opts->argv_length) || (NULL == opts->argv)) {
+	if (((1+opts->argc) >= opts->argv_length) || (NULL == opts->argv)) {
 		opts->argv_length = opts->argc + 10;
 		/*@-keeptrans@ */
 		opts->argv = realloc(opts->argv, opts->argv_length * sizeof(char *));
@@ -121,6 +122,7 @@ bool opts_add_file(opts_t opts, const char *filename)
 	 */
 
 	opts->argv[opts->argc++] = filename;
+	opts->argv[opts->argc] = NULL;
 
 	return true;
 }