[Tarantool-patches] [PATCH] build: link bundled libcurl with c-ares

[Alexander Turenko]

I brief: I would compare build times of c-ares with `./configure && make
-j` against `cmake . && make -j` and let's start with using ./configure
if the difference is not significant, but otherwise use CMake from
beginning.

See other thoughts below.

WBR, Alexander Turenko.

----

I guess that src/CMakeLists.txt will give a warning on static build: see
around `${libstatic} STREQUAL bundled-libcurl` line.

I also guess that using CMake for luajit, curl and c-ares may solve
several problems: build time, passing toolchain and Mac OS specific
flags, handling -DCMAKE_BUILD_TYPE in subprojects, clean out-of-source
build. Let's verify at least build time: if ./configure adds much time,
then we'll make other developers angry. Maybe it worth to use CMake for
c-ares from begnning.

Don't sure whether it worth to copy CMakeLists.txt from c-ares to our
cmake/ directory. Let's start w/o copy and consider to do it if we'll
need to change something.

I don't sure which pros and cons have using of ExternalProject(), it
seems we should look a bit into this.

I also don't sure whether tarantool-specific flags will be passed for
c-ares when we'll use CMake (with / without ExternalProject()). Some of
them we should pass (such as -UNDEBUG that is set by
-DCMAKE_BUILD_TYPE=Debug), some maybe not (need to verify
add_compile_flags() macro calls at least).

Sergey V. will work on
https://github.com/tarantool/tarantool/issues/4444 , maybe it worth to
cooperate. (CCed him.)

Is c-ares depends on some libraries?

WBR, Alexander Turenko.

On Mon, Nov 25, 2019 at 04:53:47PM +0300, Serge Petrenko wrote:
> libcurl has a built-in threaded resolver used for asynchronous DNS
> requests, however, when DNS server is slow to respond, the request still
> hangs tarantool until it is finished. The reason is that curl calls
> thread_join on the resolving thread internally upon timeout, making the
> calling thread hang until resolution has ended.
> Use c-ares as an asynchronous resolver instead to eliminate the problem.
> 
> Closes #4591
> ---
> https://github.com/tarantool/tarantool/issues/4591
> https://github.com/tarantool/tarantool/tree/sp/gh-4591-link-curl-with-c-ares-full-ci