Re: [PATCH for-4.6 12/13] tools/ocaml: call libxl_dominfo_{init, dispose} in stub

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 23/07/2015 08:59, Wei Liu wrote:
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> ---
> Cc: David Scott <dave.scott@eu.citrix.com>
>
> As far as I can tell, all Val_$foo function does deep-copy, so we can
> safely call dispose in said function.

Sadly this is insufficient.  failwith_xl() longjump()s back into the
ocaml runtime, which ends up leaking any allocations made for dominfo.

This is a systemic problem with the Ocaml bindings and I have a proposed
solution but it involves rewriting quite a lot of this code and is
definitely not 4.6 material.

~Andrew

> ---
>  tools/ocaml/libs/xl/xenlight_stubs.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/tools/ocaml/libs/xl/xenlight_stubs.c b/tools/ocaml/libs/xl/xenlight_stubs.c
> index 4133527..7b8d6db 100644
> --- a/tools/ocaml/libs/xl/xenlight_stubs.c
> +++ b/tools/ocaml/libs/xl/xenlight_stubs.c
> @@ -979,14 +979,18 @@ value stub_xl_dominfo_get(value ctx, value domid)
>  	int ret;
>  	uint32_t c_domid = Int_val(domid);
>  
> +	libxl_dominfo_init(&c_dominfo);
> +
>  	caml_enter_blocking_section();
>  	ret = libxl_domain_info(CTX, &c_dominfo, c_domid);
>  	caml_leave_blocking_section();
>  
> -	if (ret != 0)
> +	if (ret != 0) {
>  		failwith_xl(ERROR_FAIL, "domain_info");
> +		libxl_dominfo_dispose(&c_dominfo);
> +	}
>  	dominfo = Val_dominfo(&c_dominfo);
> -
> +	libxl_dominfo_dispose(&c_dominfo);
>  	CAMLreturn(dominfo);
>  }
>