similar to: [libnbd PATCH] generator: Prefer closure opaque after function pointer in C

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

For example nbd_set_debug takes a callback function. Previously this was defined explicitly inside the function parameters. This commit defines a new public typedef: typedef int (*nbd_debug_callback) (unsigned valid_flag, void *user_data, const char *context, const char *msg); and then uses the typedef like this: extern int nbd_set_debug_callback

The definition of functions that take a callback is changed so that the callback and user_data are combined into a single structure, eg: int64_t nbd_aio_pread (struct nbd_handle *h, void *buf, size_t count, uint64_t offset, - int (*completion_callback) (/*..*/), void *user_data, + nbd_completion_callback completion_callback, uint32_t flags); Several

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

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 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

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 discussed in this thread, the parameter is an invitation to write code with race conditions: https://www.redhat.com/archives/libguestfs/2019-July/thread.html#00309 --- docs/libnbd.pod | 6 +- examples/glib-main-loop.c | 10 ++-- examples/strict-structured-reads.c | 2 +- generator/generator | 57

As mentioned in the previous patch, there are situations where an aio client wants instant notification when a given command is complete, rather than having to maintain a separate data structure to track all in-flight commands and then iterate over that structure to learn which commands are complete. It's also desirable when writing a server validation program (such as for checking structured

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, nbd_close_callback cb); The second way is consistent with how other callbacks work

** 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

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

This is a bitmask so using an unsigned type is slightly safer. This is not an ABI change since the types are compatible. Thanks: Eric Blake. --- examples/strict-structured-reads.c | 2 +- generator/generator | 67 ++++++++++++++++-------------- interop/structured-read.c | 2 +- lib/internal.h | 2 +- tests/oldstyle.c | 2 +- 5

The original nbd_aio_* (non-callback) functions are removed and replaced with the renamed callback variants. This is a simple mechanical change to the API: (1) Any existing call to nbd_aio_*_callback can simply be renamed to nbd_aio_* (2) Any existing call to nbd_aio_* must have two extra NULL parameters added before the final flags parameter. In non-C languages, only change (1) is

We have a memory leak when a function with a closure exits early prior to registering that closure through some path that will guarantee cleanup. The easiest way to fix it is to guarantee that once a closure is passed into a public API, it will be cleaned regardless of whether that API succeeds or fails. But to avoid cleaning the closure more than once, we need to refactor our internal handling,

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

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

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, >

This is an API/ABI break, but we have not yet declared stable API. In order to use optional arguments in languages that support that, any optional arguments must be last. Let's be consistent in this by rearranging the arguments to block_status so that flags is always last. --- generator/generator | 10 ++++++---- interop/dirty-bitmap.c | 6 +++--- lib/rw.c