Subject: RE: [PATCH v2 0/8] post-v2.33 "drop support for ancient curl" follow-up

From: "Randall S. Becker" <[email-masked]>
Date: Fri, 10 Sep 2021 13:06:52 -0400

On September 10, 2021 12:53 PM, Junio C Hamano wrote:
>To: Ævar Arnfjörð Bjarmason <[email-masked]>
>Cc: [email-masked]; Jeff King <[email-masked]>; brian m . carlson <[email-masked]>; Bagas Sanjaya
><[email-masked]>
>Subject: Re: [PATCH v2 0/8] post-v2.33 "drop support for ancient curl" follow-up
>
>Ævar Arnfjörð Bjarmason  <[email-masked]> writes:
>
>> Version 1 of this had a really bad bug where we'd effectively make all
>> supported curl versions act like 7.19.4, i.e. the oldest supported
>> version except for a couple of our supported features. This is because
>> most of the things checked with the "ifdef" checks are enum fields,
>> not macros. So basically the "devil's advocate" Jeff King pointed out
>> in [2] was already the case. Oops!
>
>Wow.  Thanks for bothering to actually test ;-)
>
>Because we learned that "#ifdef CURL_SOME_FEATURE_WE_WANT" is not a generally applicable way to conditionally build for various
>features and we'd need to switch on the version numbers, it is now clear (at least to me) that the central registry approach would be a
>direction to go.
>
>> In this v2 we're instead checking LIBCURL_VERSION_NUM consistently,
>> even in those cases where we are checking things that are defined via
>> macros.
>
>Nice.
>
>>     ++ * For each X symbol we need from curl we define our own
>>     ++ * GIT_CURL_HAVE_X. If multiple similar symbols with the same prefix
>>     ++ * were defined in the same version we pick one and check for that name.
>>      + *
>>      + * Keep any symbols in date order of when their support was
>>      + * introduced, oldest first, in the official version of cURL library.
>>     @@ git-curl-compat.h (new)
>>      +/**
>>      + * CURLOPT_TCP_KEEPALIVE was added in 7.25.0, released in March 2012.
>>      + */
>>     -+#ifdef CURLOPT_TCP_KEEPALIVE
>>     ++#if LIBCURL_VERSION_NUM >= 0x071900
>>      +#define GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
>>      +#endif
>
>What we have in the posted patch is perfectly OK and serviceable, but this organization somewhat surprised me.
>
>Instead of one #if...#endif block per a feature macro, I expected to see a sequence of
>
>	/* 7.34.0 (0x072200) - Dec 2013 */
>	#if 0x072200 < VERSION
>	#define HAVE_FOO 1
>	#define HAVE_BAR 1
>	...
>	#endif
>
>	/* 7.25.0 (0x071900) - March 2012 */
>	#if 0x071900 < VERSION
>	#define HAVE_BAZ 1
>	#define HAVE_QUX 1
>	...
>        #endif
>
>
>because it would make it more clear which features can now be unconditionally used when we raise the cut-off point for the oldest
>supported version if we group these entries along the versions.
>
>Thanks.

Not that it might matter much, but both NonStop platforms are now on curl 7.78.0 and we are deploying git under OpenSSL 3 this week or next. So any objections I might previously have had are now fortunately really moot.
Cheers,
-Randall