Subject: Re: [PATCH 1/2] curl: streamline conditional compilation

From: Ævar Arnfjörð Bjarmason <[email-masked]>
Date: Wed, 16 Mar 2022 15:43:09 +0100

On Wed, Mar 16 2022, Elia Pinto wrote:

[Meta: Please chehck the -vN and --in-reply-to options to
git-format-patch et al, i.e. make a v2 a v2, and have it reply to the v1
patch or cover-letter.]

> Earlier we introduced git-curl-compat.h that defines bunch of
> GIT_CURL_HAVE_X where X is a feature of cURL library we care about,
> to make it easily manageable to conditionally compile code against
> the version of cURL library we are given.
>
> There however are two oddball macros.  Instead of checking
> GIT_CURL_HAVE_CURL_SOCKOPT_OK and using a fallback definition for
> CURL_SOCKOPT_OK macro, we just defined CURL_SOCKOPT_OK to a safe
> value when compiling against an old version that lack the symbol.

The way it was being done before was intentional & discused on list.

See my original
https://lore.kernel.org/git/[email-masked]/
which did it pretty much like that, and Junio's subsequent
follow-up. I.e. this breadcrumb trail:
https://lore.kernel.org/git/?q=CURL_SOCKOPT_OK

> -#if LIBCURL_VERSION_NUM < 0x071505
> -#define CURL_SOCKOPT_OK 0
> +#if LIBCURL_VERSION_NUM >= 0x071505
> +#define GIT_CURL_HAVE_CURL_SOCKOPT_OK 1
>  #endif

IOW we should drop this.

>  /**
>   * CURLOPT_TCP_KEEPALIVE was added in 7.25.0, released in March 2012.
>   */
>  #if LIBCURL_VERSION_NUM >= 0x071900
> -#define GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
> +#define GIT_CURL_HAVE_CURLOPT_TCP_KEEPALIVE 1
>  #endif

This change is good.

> diff --git a/http.c b/http.c
> index 229da4d148..d7ad7db1d6 100644
> --- a/http.c
> +++ b/http.c
> @@ -517,7 +517,7 @@ static int has_proxy_cert_password(void)
>  }
>  #endif
>  
> -#ifdef GITCURL_HAVE_CURLOPT_TCP_KEEPALIVE
> +#ifdef GIT_CURL_HAVE_CURLOPT_TCP_KEEPALIVE
>  static void set_curl_keepalive(CURL *c)
>  {

As is this.

>  	curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);
> @@ -536,7 +536,9 @@ static int sockopt_callback(void *client, curl_socket_t fd, curlsocktype type)
>  	rc = setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&ka, len);
>  	if (rc < 0)
>  		warning_errno("unable to set SO_KEEPALIVE on socket");
> -
> +#ifndef GIT_CURL_HAVE_CURL_SOCKOPT_OK
> +#define CURL_SOCKOPT_OK 0
> +#endif
>  	return CURL_SOCKOPT_OK;
>  }

The whole point of git-curl-compat.h and its big-brother
git-compat-util.h is that we'd prefer not to have such hacks inline if
at all possible.

For most of the GIT_CURL_* stuff we need to since it's conditionally
using symbols etc., but in this case we can just define a fallback
centrally and not worry about it in the code.

So the pre-image really is much better.