Add new fuzzers for command parsing, formats and styles, from David Korczynski

in GitHub issue 4957.

fuzz/format-fuzzer.c

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) 2026 David Korczynski <david@adalogics.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF MIND, USE, DATA OR PROFITS, WHETHER
+ * IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
+ * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * Fuzz the tmux format string expander (format_expand).
+ *
+ * This exercises:
+ *   - format.c (format parsing, modifier chains, conditionals, math, regex)
+ *   - colour.c (colour name and RGB parsing within formats)
+ *   - utf8.c (UTF-8 width calculations in format padding)
+ */
+
+#include <stddef.h>
+#include <string.h>
+
+#include "tmux.h"
+
+struct event_base *libevent;
+
+int
+LLVMFuzzerTestOneInput(const u_char *data, size_t size)
+{
+	struct format_tree	*ft;
+	char			*buf, *expanded;
+
+	if (size > 2048 || size == 0)
+		return 0;
+
+	/* Null-terminate the input for format_expand. */
+	buf = malloc(size + 1);
+	if (buf == NULL)
+		return 0;
+	memcpy(buf, data, size);
+	buf[size] = '\0';
+
+	ft = format_create(NULL, NULL, 0, FORMAT_NOJOBS);
+	format_add(ft, "session_name", "%s", "fuzz-session");
+	format_add(ft, "window_index", "%d", 0);
+	format_add(ft, "window_name", "%s", "fuzz-window");
+	format_add(ft, "pane_index", "%d", 0);
+	format_add(ft, "pane_id", "%s", "%%0");
+	format_add(ft, "host", "%s", "fuzzhost");
+	format_add(ft, "pane_width", "%d", 80);
+	format_add(ft, "pane_height", "%d", 25);
+
+	expanded = format_expand(ft, buf);
+	free(expanded);
+	format_free(ft);
+
+	free(buf);
+	return 0;
+}
+
+int
+LLVMFuzzerInitialize(__unused int *argc, __unused char ***argv)
+{
+	const struct options_table_entry	*oe;
+
+	global_environ = environ_create();
+	global_options = options_create(NULL);
+	global_s_options = options_create(NULL);
+	global_w_options = options_create(NULL);
+	for (oe = options_table; oe->name != NULL; oe++) {
+		if (oe->scope & OPTIONS_TABLE_SERVER)
+			options_default(global_options, oe);
+		if (oe->scope & OPTIONS_TABLE_SESSION)
+			options_default(global_s_options, oe);
+		if (oe->scope & OPTIONS_TABLE_WINDOW)
+			options_default(global_w_options, oe);
+	}
+	libevent = osdep_event_init();
+	socket_path = xstrdup("dummy");
+
+	return 0;
+}