Re: [dpdk-dev] [PATCH v2 1/7] cmdline: make implementation opaque

["Kinsella, Ray" <mdr@ashroe.eu>]

On 17/09/2020 14:34, Olivier Matz wrote:
> Hi Dmitry,
> 
> On Fri, Jul 31, 2020 at 12:06:45AM +0300, Dmitry Kozlyuk wrote:
>> struct cmdline exposes platform-specific members it contains, most
>> notably struct termios that is only available on Unix. Make the
>> structure opaque.
>>
>> Remove tests checking struct cmdline content as meaningless.
>>
>> Add cmdline_get_rdline() to access history buffer.
>> The new function is currently used only in tests.
>>
>> Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
> 
> First, please forgive me for the very late feedback. It is all the more
> problematic because I think this patch introduces an ABI breakage, that
> should have been announced.

I think this is more a theoretical ABI breakage, than a real ABI breakage.
As the consuming application is never likely to access the structure, 
As in most cases, I doubt it ever has any knowledge of the structure. 

My 2c, is that I think it is fine not consider this as ABI breakage. 

> 
> Making cmdline struct opaque clearly goes in the right direction, as
> it will prevent future ABI breakage.
> 
> In my opinion, we could accept the patch for 20.11, knowing it reduce
> the risk of future ABI breakage, and that cmdline is not a core
> component of DPDK. However it has to be discussed and accepted by other
> people.
> 
> Else, the patch would be delayed for 21.11. From what I see from the
> other patches, it looks possible to keep cmdline struct public without
> breaking the existing ABI by adding #ifdef CONFIG_RTE_EXEC_ENV_WINDOWS,
> is it correct?
> 
> One minor comment below:
> 
>> --- a/app/test/test_cmdline_lib.c
>> +++ b/app/test/test_cmdline_lib.c
>> @@ -46,22 +46,29 @@ complete_buffer(__rte_unused struct rdline *rdl,
>>  static int
>>  test_cmdline_parse_fns(void)
>>  {
>> -	struct cmdline cl;
>> +	struct cmdline *cl;
>> +	cmdline_parse_ctx_t ctx;
>>  	int i = 0;
>>  	char dst[CMDLINE_TEST_BUFSIZE];
>>  
>> +	cl = cmdline_new(&ctx, "prompt", -1, -1);
>> +	if (cl == NULL) {
>> +		printf("Error: cannot create cmdline to test parse fns!\n");
>> +		return -1;
>> +	}
>> +
>>  	if (cmdline_parse(NULL, "buffer") >= 0)
>>  		goto error;
>> -	if (cmdline_parse(&cl, NULL) >= 0)
>> +	if (cmdline_parse(cl, NULL) >= 0)
>>  		goto error;
>>  
>>  	if (cmdline_complete(NULL, "buffer", &i, dst, sizeof(dst)) >= 0)
>>  		goto error;
>> -	if (cmdline_complete(&cl, NULL, &i, dst, sizeof(dst)) >= 0)
>> +	if (cmdline_complete(cl, NULL, &i, dst, sizeof(dst)) >= 0)
>>  		goto error;
>> -	if (cmdline_complete(&cl, "buffer", NULL, dst, sizeof(dst)) >= 0)
>> +	if (cmdline_complete(cl, "buffer", NULL, dst, sizeof(dst)) >= 0)
>>  		goto error;
>> -	if (cmdline_complete(&cl, "buffer", &i, NULL, sizeof(dst)) >= 0)
>> +	if (cmdline_complete(cl, "buffer", &i, NULL, sizeof(dst)) >= 0)
>>  		goto error;
>>  
>>  	return 0;
>> @@ -166,11 +173,11 @@ static int
>>  test_cmdline_fns(void)
>>  {
>>  	cmdline_parse_ctx_t ctx;
>> -	struct cmdline cl, *tmp;
>> +	struct cmdline *cl;
>>  
>>  	memset(&ctx, 0, sizeof(ctx));
>> -	tmp = cmdline_new(&ctx, "test", -1, -1);
>> -	if (tmp == NULL)
>> +	cl = cmdline_new(&ctx, "test", -1, -1);
>> +	if (cl == NULL)
>>  		goto error;
>>  
>>  	if (cmdline_new(NULL, "prompt", 0, 0) != NULL)
>> @@ -179,7 +186,7 @@ test_cmdline_fns(void)
>>  		goto error;
>>  	if (cmdline_in(NULL, "buffer", CMDLINE_TEST_BUFSIZE) >= 0)
>>  		goto error;
>> -	if (cmdline_in(&cl, NULL, CMDLINE_TEST_BUFSIZE) >= 0)
>> +	if (cmdline_in(cl, NULL, CMDLINE_TEST_BUFSIZE) >= 0)
>>  		goto error;
>>  	if (cmdline_write_char(NULL, 0) >= 0)
>>  		goto error;
>> @@ -188,31 +195,14 @@ test_cmdline_fns(void)
>>  	cmdline_set_prompt(NULL, "prompt");
>>  	cmdline_free(NULL);
>>  	cmdline_printf(NULL, "format");
>> -	/* this should fail as stream handles are invalid */
>> -	cmdline_printf(tmp, "format");
>>  	cmdline_interact(NULL);
>>  	cmdline_quit(NULL);
>>  
>> -	/* check if void calls change anything when they should fail */
>> -	cl = *tmp;
>> -
>> -	cmdline_printf(&cl, NULL);
>> -	if (memcmp(&cl, tmp, sizeof(cl))) goto mismatch;
>> -	cmdline_set_prompt(&cl, NULL);
>> -	if (memcmp(&cl, tmp, sizeof(cl))) goto mismatch;
>> -	cmdline_in(&cl, NULL, CMDLINE_TEST_BUFSIZE);
>> -	if (memcmp(&cl, tmp, sizeof(cl))) goto mismatch;
>> -
>> -	cmdline_free(tmp);
>> -
>>  	return 0;
>>  
>>  error:
>>  	printf("Error: function accepted null parameter!\n");
>>  	return -1;
>> -mismatch:
>> -	printf("Error: data changed!\n");
>> -	return -1;
> 
> cmdline_free(cl) is missing.
> 
> before your patch, cmdline_free(tmp) was already missing in error case
> by the way.
> 
> 
> Thanks,
> Olivier
>