similar to: [PATCH libnbd] generator: Swap parameters of nbd_add_close_callback.

Existing practice tends to prefer the void* closure argument for C callbacks to occur after the function pointer (POSIX: pthread_create; glibc: qsort_r; glib: g_thread_new; libvirt: virConnectDomainEventRegisterAny; etc.). It's also handy to think that calling 'myfunc(cb, arg)' will eventually result in a call to 'cb(arg)'. While I couldn't quickly find any style guide

On 7/16/19 10:39 AM, Eric Blake wrote: > On 7/16/19 10:04 AM, Richard W.M. Jones wrote: >> The API changes from: >> >> int nbd_add_close_callback (struct nbd_handle *h, >> nbd_close_callback cb, >> void *user_data); >> >> to: >> >> int nbd_add_close_callback (struct nbd_handle

A Closure is a list of (usually one, but can be more) closures. In C there is also a singe ‘void *user_data’ parameter which is passed by the caller into the function and through as the first parameter of each callback invocation. By grouping the previously separate Opaque and Callback* parameters together we can avoid the awkward situation where we have to scan through the argument list to try

We previously needed nbd_add_close_callback to do cleanup from language bindings. However now we have closure lifetimes this is no longer needed and can be removed. See also: https://www.redhat.com/archives/libguestfs/2019-July/msg00213.html --- generator/generator | 18 ------------------ lib/handle.c | 35 ----------------------------------- lib/internal.h | 10 ---------- 3 files

On 7/16/19 6:04 AM, Richard W.M. Jones wrote: > A Closure is a list of (usually one, but can be more) closures. In C > there is also a singe ‘void *user_data’ parameter which is passed by > the caller into the function and through as the first parameter of > each callback invocation. > > By grouping the previously separate Opaque and Callback* parameters > together we can

On Tue, Jul 16, 2019 at 11:38:36AM -0500, Eric Blake wrote: > On 7/16/19 10:39 AM, Eric Blake wrote: > > On 7/16/19 10:04 AM, Richard W.M. Jones wrote: > >> The API changes from: > >> > >> int nbd_add_close_callback (struct nbd_handle *h, > >> nbd_close_callback cb, > >> void

In preparation for closure lifetimes, split up the Closure so it no longer describes a list of closures, but a single callback. This changes the API because functions which take 2 or more closures now pass a separate user_data for each one. --- docs/libnbd.pod | 3 +- examples/strict-structured-reads.c | 2 +- generator/generator | 760

On 7/16/19 10:04 AM, Richard W.M. Jones wrote: > The API changes from: > > int nbd_add_close_callback (struct nbd_handle *h, > nbd_close_callback cb, > void *user_data); > > to: > > int nbd_add_close_callback (struct nbd_handle *h, > void *user_data, >

Previously closures had a crude flag which tells if they are persistent or transient. Transient closures (flag = false) last for the lifetime of the currently called libnbd function. Persistent closures had an indefinite lifetime which could last for as long as the handle. In language bindings handling persistent closures was wasteful as we needed to register a "close callback" to

Previously closures had a crude flag which tells if they are persistent or transient. Transient closures (flag = false) last for the lifetime of the currently called libnbd function. Persistent closures had an indefinite lifetime which could last for as long as the handle. In language bindings handling persistent closures was wasteful as we needed to register a "close callback" to

** INCOMPLETE ** This is the generator change as discussed on the list already. The Python and OCaml bindings are not yet done. It passes all [C only] tests and valgrind. Note that nbd_add_close_callback is inconsistent with other closure types because it passes the user_data parameter after the function. (This is not caused by the current patch, it was already inconsistent). We decided that

Previously closures had a crude flag which tells if they are persistent or transient. Transient closures (flag = false) last for the lifetime of the currently called libnbd function. Persistent closures had an indefinite lifetime which could last for as long as the handle. In language bindings handling persistent closures was wasteful as we needed to register a "close callback" to

As before, but this one has working Python bindings. OCaml still TBD. Rich.

Make it easier for C libraries to consume arbitrary versions of libnbd, by giving a probe for which functions the current version of the library exports. --- I'm fuzzy enough on OCaml that I'll get review for this, although I like the resulting libnbd.h. generator/generator | 24 +++++++++++++++++++++++- 1 file changed, 23 insertions(+), 1 deletion(-) diff --git a/generator/generator

I think I've addressed everything that was raised in review. Some of the highlights: - Callbacks should be freed reliably along all exit paths. - There's a simple test of closure lifetimes. - I've tried to use VALID|FREE in all the places where I'm confident that it's safe and correct to do. There may be more places. Note this is an optimization and shouldn't

This implements most of what I wrote here: https://www.redhat.com/archives/libguestfs/2019-July/msg00213.html

v1 was here: https://www.redhat.com/archives/libguestfs/2019-July/thread.html#00231 The changes address everything that Eric picked up in his review of the first two patches. I have also added two more patches (4 and 5) which respectively fix docs and change int status -> unsigned status, as discussed. Passes make, check, check-valgrind. Rich.

On 7/24/19 7:17 AM, Richard W.M. Jones wrote: > In preparation for closure lifetimes, split up the Closure so it no > longer describes a list of closures, but a single callback. > > This changes the API because functions which take 2 or more closures > now pass a separate user_data for each one. > --- > docs/libnbd.pod | 3 +- >

h.nbd_connect_command was leaking a python object per parameter, and also leaks memory on failure. In fact, it was possible to segfault on something as trivial as: nbdsh -c 'h.connect_command(["true",1])' h.nbd_pread was leaking a read buffer on every single synchronous read. My previous patch to address closure callbacks had a bug in h.nbd_pread_structured and similar: if the

Inspection of the generated code showed several places where we did not release references on all error paths. In particular, switching things to always jump to an out: label, even when the underlying C function cannot fail, makes it easier to clean up when the user passes wrong types to a function call. One of the easiest triggers without this patch was this one-liner: $ nbdsh -c