Re: [PATCH 7/7] t/helper/simple-ipc: convert test-simple-ipc to use start_bg_command
- From
- Jeff Hostetler <git@jeffhostetler.com>
- Date
- Sep 17, 2021, 19:41 UTC
- Message-ID
- <aaad241c-4014-729c-32c9-df7039439a77@jeffhostetler.com>
- In-Reply-To
- <YULQ8DJFKlrOml8Z@nand.local>
On 9/16/21 1:06 AM, Taylor Blau wrote:
Show 46 quoted lines
> On Wed, Sep 15, 2021 at 08:36:17PM +0000, Jeff Hostetler via GitGitGadget wrote:
>> From: Jeff Hostetler <jeffhost@microsoft.com>
>>
>> Convert test helper to use `start_bg_command()` when spawning a server
>> daemon in the background rather than blocks of platform-specific code.
>>
>> Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
>> ---
>> t/helper/test-simple-ipc.c | 193 ++++++++-----------------------------
>> 1 file changed, 40 insertions(+), 153 deletions(-)
>>
>> diff --git a/t/helper/test-simple-ipc.c b/t/helper/test-simple-ipc.c
>> index 91345180750..59a950f3b00 100644
>> --- a/t/helper/test-simple-ipc.c
>> +++ b/t/helper/test-simple-ipc.c
>> @@ -9,6 +9,7 @@
>> #include "parse-options.h"
>> #include "thread-utils.h"
>> #include "strvec.h"
>> +#include "run-command.h"
>>
>> #ifndef SUPPORTS_SIMPLE_IPC
>> int cmd__simple_ipc(int argc, const char **argv)
>> @@ -274,178 +275,64 @@ static int daemon__run_server(void)
>> return ret;
>> }
>>
>> -#ifndef GIT_WINDOWS_NATIVE
>> -/*
>> - * This is adapted from `daemonize()`. Use `fork()` to directly create and
>> - * run the daemon in a child process.
>> - */
>> -static int spawn_server(pid_t *pid)
>> -{
>> - struct ipc_server_opts opts = {
>> - .nr_threads = cl_args.nr_threads,
>> - };
>> +static start_bg_wait_cb bg_wait_cb;
>
> This whole patch is delightful to read, as the new implementation is so
> much cleaner as a result of the earlier work in this series.
>
> Am I correct in assuming that this is to encourage a compiler error if
> bg_wait_cb does not satisfy the type of start_bg_wait_cb? If so, then I
> think we are already getting that by trying to pass bg_wait_cb to
> start_bg_command().I use that trick to get the compiler to give me a compiler error at the point of the function declaration.
For example, If I add an arg to the function that doesn't match what's in the prototype definition, I get:
t/helper/test-simple-ipc.c:280:12: error: conflicting types for 'bg_wait_cb'
static int bg_wait_cb(const struct child_process *cp, void *cb_data, int
foo)
^
t/helper/test-simple-ipc.c:278:25: note: previous declaration is here
static start_bg_wait_cb bg_wait_cb;
^
1 error generated.Yes, we may get an error when the function pointer is referenced in start_bg_command() or if we're using it to initialize a vtable or something, but those errors are further away from the actual error (and sometimes they can be a little cryptic).
Also, it helps document that this function's signature is predefined for a reason.
It's a quirky trick I know, but it has served me well over the years.
Show 58 quoted lines
>
> E.g., applying this (intentionally broken) diff on top:
>
> --- 8< ---
>
> diff --git a/t/helper/test-simple-ipc.c b/t/helper/test-simple-ipc.c
> index 59a950f3b0..3aed787206 100644
> --- a/t/helper/test-simple-ipc.c
> +++ b/t/helper/test-simple-ipc.c
> @@ -275,9 +275,7 @@ static int daemon__run_server(void)
> return ret;
> }
>
> -static start_bg_wait_cb bg_wait_cb;
> -
> -static int bg_wait_cb(void *cb_data, const struct child_process *cp)
> +static int bg_wait_cb(const void *cb_data, const struct child_process *cp)
> {
> int s = ipc_get_active_state(cl_args.path);
>
> --- >8 ---
>
> and then compiling still warns of a mismatched type when calling
> start_bg_command().
>
>> - *pid = fork();
>> -
>> - switch (*pid) {
>> - case 0:
>> - if (setsid() == -1)
>> - error_errno(_("setsid failed"));
>> - close(0);
>> - close(1);
>> - close(2);
>> - sanitize_stdfds();
>> +static int bg_wait_cb(void *cb_data, const struct child_process *cp)
>> +{
>> + int s = ipc_get_active_state(cl_args.path);
>>
>> - return ipc_server_run(cl_args.path, &opts, test_app_cb,
>> - (void*)&my_app_data);
>> + switch (s) {
>> + case IPC_STATE__LISTENING:
>> + /* child is "ready" */
>> + return 0;
>>
>> - case -1:
>> - return error_errno(_("could not spawn daemon in the background"));
>> + case IPC_STATE__NOT_LISTENING:
>> + case IPC_STATE__PATH_NOT_FOUND:
>> + /* give child more time */
>> + return 1;
>>
>> default:
>
> I'm always a little hesitant to have default cases when switch over enum
> types, since it suppresses the warning when there's a new value of that
> type. But we already have a similar default in client__probe_server().Do all compilers now handle switching over an enum and detect unhandled cases? Once upon a time that wasn't the case IIRC.
Show 7 quoted lines
>... > > Ditto. > > Thanks, > Taylor >