vis:pipe(): don't segfault if vis->win isn't present

When `file` was made optional the variable was changed to be initialized
by `vis->win->file` instead of a known safe file pointer. If `vis:pipe()`
is called based on the event `FILE_OPEN` the `file` parameter can be
valid even when `vis->win` is not yet present. Assuming `file` was
provided this would be handled later on if vis didn't segfault. By
initializing to NULL when `vis->win` isn't present `file` is given
a chance be handled later. In the case where `file` wasn't given and
`vis->win` is missing an error is thrown and `vis:pipe()` exits.

fixes #1107 - Lua API: vis:pipe() causes a segfault when called before
a window is open

1 files changed, 5 insertions, 1 deletions

diff --git a/vis-lua.c b/vis-lua.c
index e304dd7..ab7f6f4 100644
--- a/vis-lua.c
+++ b/vis-lua.c
@@ -1340,7 +1340,7 @@ static int pipe_func(lua_State *L) {
 	Vis *vis = obj_ref_check(L, 1, "vis");
 	int cmd_idx = 4;
 	char *out = NULL, *err = NULL;
-	File *file = vis->win->file;
+	File *file = vis->win ? vis->win->file : NULL;
 	Filerange range = text_range_new(0, 0);
 	if (lua_gettop(L) <= 3) {
 		cmd_idx = 2;
@@ -1350,6 +1350,10 @@ static int pipe_func(lua_State *L) {
 	}
 	const char *cmd = luaL_checkstring(L, cmd_idx);
 	bool fullscreen = lua_isboolean(L, cmd_idx + 1) && lua_toboolean(L, cmd_idx + 1);
+	
+	if (!file)
+		return luaL_error(L, "vis:pipe(cmd = '%s'): win not open, file can't be nil", cmd);
+
 	int status = vis_pipe_collect(vis, file, &range, (const char*[]){ cmd, NULL }, &out, &err, fullscreen);
 	lua_pushinteger(L, status);
 	if (out)