Yes, I've used that solution too, keeping a static fixed string around,
it's just not very nice and will break if it's ever multithreaded.
Immanuel

On Sat, Dec 3, 2016 at 2:20 PM, Richard W.M. Jones <rich@annexia.org> wrote:

> On Mon, Nov 28, 2016 at 03:39:05PM +0100, immanuel litzroth wrote:
> > caml_invalid_argument(str) is no return and does not free it's
> > argument.
> > So calling it with a string constructed dynamically will mean it'll never
> > get freed.
> > I could construct an ocaml string and pass that to caml_raise_with_arg,
> > but I don't seem to be able to get to the caml_exn_Invalid_argument from
> > c. Am I missing something?
>
> We have the same problem in libguestfs in a few places.  The solution
> is to use an allocation on the C stack, either a fixed size buffer or
> [although we don't currently use this] a variable sized one using
> alloca.  The string is freed when the stack is unwound.  Examples:
>
> https://github.com/libguestfs/libguestfs/blob/master/
> builder/yajl-c.c#L108-L114
> https://github.com/libguestfs/libguestfs/blob/master/v2v/
> domainxml-c.c#L120
>
> Be nice to have a "freeing" version of caml_raise* I suppose.
>
> Rich.
>