Re: [Tarantool-patches] [PATCH v2 1/2] build: link bundled libcurl with c-ares

[Serge Petrenko <sergepetrenko@tarantool.org>]

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Hi! Thanks for the review! I fixed your comments and performed the actions you expected me
to perform, except one. More info inline. The diff is below.

> 8 февр. 2020 г., в 22:42, Alexander Turenko <alexander.turenko@tarantool.org> написал(а):
> 
> I mostly okay with the patch, but expect several actions like filing
> some issues against c-ares and curl and minor tweaks of the patch.
> 
> Re blocking in threaded resolver
> --------------------------------
> 
> Let's file an issue to curl, because it is inappropriate to block an
> application that expect libcurl to give a control if something would
> block. An error like 'DNS resolver thread pool is exhausted' is better,
> because it can be handled on an application side somehow:
> 
> * do other work / be responsible until free resolver threads will be
>  available;
> * give a user an error for further requests;
> * dynamically increase threads count (automatically or upon a user
>  request).

There already exist 2 issues: [1] - closed by a bot, unintentionally, I think.
[2] - a duplicate of [1]. 

> 
> Re ExternalProject
> ------------------
> 
> In brief: let's file another issue as described below and postpone
> further activities.
> 
> There is the way to link c-ares into libcurl w/o installing c-ares using
> a pkgconfig file, because it allows to set different include and library
> directories and is supported by libcurl's configure script (see [1]).
> 
> This however cannot be used with CMake (I didn't find a way). I propose
> to file an issue (or even a PR) to curl to support different directories
> for include and library files for c-ares (in CMake build). The
> motivation is to use libcurl + c-ares as part of a parent build process
> (like we going to do). It seems we just need to add two hints (one for
> an include directory and one for a library directory) to
> ${CURL}/CMake/FindCARES.cmake (see [2]) like we do in
> tarantool/modulekit (see [3]).

I’ll think some more about the issue you propose, and file it as soon as I
come up with good wording and reasoning. I’m a little bit out of context
right now.

> 
> Anyway, I'm okay with ExternalProject() and so installation of c-ares as
> a part of build process for now. Hopefully we'll change it in the future
> and so we'll not need to adjust flags like -isysroot in our cmake files.
> 
> Re c-ares dependencies
> ----------------------
> 
> See [4].
> 
> Other
> -----
> 
> BTW, maybe file another issue to lower minimal required CMake version is
> c-ares to 2.8?

I’ve opened the pull request in c-ares repo [3].
I’ve updated the minimum cmake version to 2.8.12. This is the versrion we tested
on and the version that used to be the minimal requirement before it was raised to 3+.

> 
> [1]: https://github.com/curl/curl/issues/2203
> [2]: https://github.com/curl/curl/blob/5ce7102ceae250e2d31b54aad2f33b3bc35f243a/CMake/FindCARES.cmake
> [3]: https://github.com/tarantool/modulekit/blob/0994d76d57cc42dd107bd2a9ddcd04ddc91f52da/FindTarantool.cmake#L12
> [4]: https://lists.tarantool.org/pipermail/tarantool-patches/2020-February/014024.html
> 
> ----
> 
>> +    set(ARES_CMAKE_FLAGS "-DCARES_STATIC=ON")
>> +    list(APPEND ARES_CMAKE_FLAGS "-DCARES_SHARED=OFF")
>> +    list(APPEND ARES_CMAKE_FLAGS "-DCARES_BUILD_TOOLS=OFF")
>> +    # We buid both static and shared versions of curl, so ares
> 
> Typo: buid.

Fixed.

> 
>> diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
>> index e12de6005..bdeec5f89 100644
>> --- a/src/CMakeLists.txt
>> +++ b/src/CMakeLists.txt
>> @@ -227,7 +227,8 @@ if(BUILD_STATIC)
>>             list(APPEND EXPORT_LIST ${SYMBOLS_LIB})
>>             # set variable to allow rescan (CMake depended)
>>             set(SYMBOLS_LIB "SYMBOLS_LIB-NOTFOUND")
>> -        elseif (${libstatic} STREQUAL bundled-libcurl)
>> +        elseif (${libstatic} STREQUAL bundled-libcurl OR
>> +                ${libstatic} STREQUAL bundled-ares)
>>             message("We don't need to export symbols from statically linked libcurl, skipped")
> 
> It would be good to adjust the message using ${libstatic} (because not
> it is not only about libcurl).

Fixed

I’ve also fixed your comments from [4], added an empty ARES_LIBRARIES var as a placeholder,
and filed an issue to c-ares regarding CMake linking unnecessary libraries [5].

Speaking of linking with unnecessary libraries, as you pointed out in [4], I just left it as-is for now,
since everything works in our CI. We may disable the libs altogether later, if it is needed.

[1]: https://github.com/curl/curl/issues/2975 <https://github.com/curl/curl/issues/2975>
[2]: https://github.com/curl/curl/issues/4852 <https://github.com/curl/curl/issues/4852>
[3]: https://github.com/c-ares/c-ares/pull/306 <https://github.com/c-ares/c-ares/pull/306>
[4]: https://lists.tarantool.org/pipermail/tarantool-patches/2020-February/014024.html <https://lists.tarantool.org/pipermail/tarantool-patches/2020-February/014024.html>
[5]: https://github.com/c-ares/c-ares/issues/307 <https://github.com/c-ares/c-ares/issues/307>

diff --git a/cmake/BuildAres.cmake b/cmake/BuildAres.cmake
index 0f9f174ce..a38fa8f30 100644
--- a/cmake/BuildAres.cmake
+++ b/cmake/BuildAres.cmake
@@ -13,7 +13,7 @@ macro(ares_build)
     set(ARES_CMAKE_FLAGS "-DCARES_STATIC=ON")
     list(APPEND ARES_CMAKE_FLAGS "-DCARES_SHARED=OFF")
     list(APPEND ARES_CMAKE_FLAGS "-DCARES_BUILD_TOOLS=OFF")
-    # We buid both static and shared versions of curl, so ares
+    # We build both static and shared versions of curl, so ares
     # has to be built with -fPIC for the shared version.
     list(APPEND ARES_CMAKE_FLAGS "-DCARES_STATIC_PIC=ON")
     # Even though we set the external project's install dir
@@ -53,6 +53,7 @@ macro(ares_build)
     set_target_properties(bundled-ares PROPERTIES IMPORTED_LOCATION
         ${ARES_INSTALL_DIR}/lib/libcares.a)
     add_dependencies(bundled-ares bundled-ares-project)
+    set(ARES_LIBRARIES bundled-ares)
 
     unset(ARES_CMAKE_FLAGS)
     unset(ARES_CFLAGS)
diff --git a/cmake/BuildLibCURL.cmake b/cmake/BuildLibCURL.cmake
index 756297878..5f8b15a63 100644
--- a/cmake/BuildLibCURL.cmake
+++ b/cmake/BuildLibCURL.cmake
@@ -164,7 +164,7 @@ macro(curl_build)
     set(CURL_INCLUDE_DIRS ${LIBCURL_INSTALL_DIR}/include)
     set(CURL_LIBRARIES bundled-libcurl ${LIBZ_LIBRARY})
     if (BUNDLED_LIBCURL_USE_ARES)
-        set(CURL_LIBRARIES ${CURL_LIBRARIES} bundled-ares)
+        set(CURL_LIBRARIES ${CURL_LIBRARIES} ${ARES_LIBRARIES})
     endif()
     if (TARGET_OS_LINUX OR TARGET_OS_FREEBSD)
         set(CURL_LIBRARIES ${CURL_LIBRARIES} rt)
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index bdeec5f89..7d865472d 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -229,7 +229,7 @@ if(BUILD_STATIC)
             set(SYMBOLS_LIB "SYMBOLS_LIB-NOTFOUND")
         elseif (${libstatic} STREQUAL bundled-libcurl OR
                 ${libstatic} STREQUAL bundled-ares)
-            message("We don't need to export symbols from statically linked libcurl, skipped")
+            message("We don't need to export symbols from statically linked ${libstatic}, skipped")
         else()
             message(WARNING "${libstatic} should be a static")
         endif()
diff --git a/third_party/c-ares b/third_party/c-ares
index 56a74c501..bbbffa4da 160000
--- a/third_party/c-ares
+++ b/third_party/c-ares
@@ -1 +1 @@
-Subproject commit 56a74c501a615c16ca54d608d1796e966f9a503a
+Subproject commit bbbffa4da8baf35b0e4e1c376e38018f9a8bcb4e

--
Serge Petrenko
sergepetrenko@tarantool.org


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