Re: LUA + musl, garbage collection issue?

[Szabolcs Nagy <nsz@port70.net>]

* Scott Valentine <scottvalen@hotmail.com> [2014-09-23 19:25:47 -1000]:
> 
> In any case, this has been a nasty issue to track down. I have surely traced it to the following code block in luci (by process of elimination):
> 
>         local fp
>         luci.http.setfilehandler(
>                 function(meta, chunk, eof)
>                         if not fp then
>                                 if meta and meta.name == "image" then
>                                         fp = io.open(image_tmp, "w")
>                                 else
>                                         fp = io.popen(restore_tmp, "w")
>                                 end
>                         end
>                         if chunk then
>                                 fp:write(chunk)
>                         end
>                         if eof then
>                                 fp:close()
>                         end
>                 end
>         )
> 
> 
> Here, "chunk" is a 2048 byte string, and the library calls are to nixio:
> 

are you sure the nixio function is called?

if fp is not set then io.open is called which should
use libc fopen, so fp:write should be a wrapper around
fwrite

if the code really calls the nixio function below then
there is no stdio involved, it directly writes to an fd

> static int nixio_file_write(lua_State *L) {
>         int fd = nixio__checkfd(L, 1);
>         size_t len;
>         ssize_t sent;
>         const char *data = luaL_checklstring(L, 2, &len);
> 
>         if (lua_gettop(L) > 2) {
>                 int offset = luaL_optint(L, 3, 0);
>                 if (offset) {
>                         if (offset < len) {
>                                 data += offset;
>                                 len -= offset;
>                         } else {
>                                 len = 0;
>                         }
>                 }
> 
>                 unsigned int wlen = luaL_optint(L, 4, len);
>                 if (wlen < len) {
>                         len = wlen;
>                 }
>         }
> 
>         do {
>                 sent = write(fd, data, len);
>         } while(sent == -1 && errno == EINTR);
>         if (sent >= 0) {
>                 lua_pushinteger(L, sent);
>                 return 1;
>         } else {
>                 return nixio__perror(L);
>         }
> }
> 


> When I have time, I'll do a build against eglibc with a reduced BUFSIZ = 1024 (musl's default) and see if the problem is reproduced.
> 

i think you should try to reproduce the bug with a minimal
test-case where either stdio (io.*) is called or nixio only