[tarantool-patches] [PATCH] build: fix OpenSSL linking problems on FreeBSD

[Alexander Turenko]

FreeBSD has OpenSSL as part of the base system: libraries are located in
/usr/lib, headers are in /usr/include. However a user may install the
library into /usr/local/{lib,include} from ports / pkg. In this case
tarantool did choose /usr/local version, while libcurl will pick up a
base system library. This is fixed by passing --with-ssl option with an
argument (/usr/local or /usr if custom -DOPENSSL_ROOT_DIR=<...> is not
passed).

Now the behaviour is the following. If -DOPENSSL_ROOT_DIR=<...> is
passed, then try to use OpenSSL from it. Otherwise find the library in
/usr/local and then in /usr. This is right as for tarantool's crypto
module as well as for libcurl submodule.

There is a flaw here: a user is unable to choose a base system library
if a ports / pkg version of OpenSSL is installed. The reason here is
that tarantool's crypto module depends on other libraries and
-I/usr/local/include may be added to build options. I have no good
solution for that, so `cmake . -DOPENSSL_ROOT_DIR=/usr` will give a
warning on FreeBSD and `gmake` likely will fail if libraries are of
different versions (see cmake/os.cmake comments for more information).
See also a [discussion][1] in FreeBSD community about all those /usr and
/usr/local problems.

There were two other problems that may fail tarantool build on FreeBSD:
they are fixed in this commit and described below.

First, libcurl's configure script chooses GCC by default if it exists
(say, installed from ports / pkg). It is unexpected behaviour when
tarantool sources itself are built with clang. Now it is fixed by
passing a compiler explicitly to the libcurl's configure script: the
library will use base system clang by default or one that a user pass to
tarantool's cmake.

Side note: GCC has /usr/local/include in its default headers search
paths; libcurl's configure script chooses GCC as a compiler and OpenSSL
from a base system by default that leads to OpenSSL header / library
mismatch. It is the primary reason of the build fail that was fixed in
1f2338bd809585b0b38fe07fd9f80c31747374c2 ('build: FreeBSD packages
installation'). It is not much relevant anymore, because we don't try to
link with a base system OpenSSL if /usr/local one exists (if it is asked
explicitly with -DOPENSSL_ROOT_DIR=<...> we'll do, but will give a
warning). Anyway, it is important to know such details if we'll change
build scripts in a future.

Second, backtraces are not supported on FreeBSD, but were enabled if
libunwind headers is found. This leads to an error on cmake stage,
because of unability to find a right library (this is the bug). Now we
disable backtraces on FreeBSD by default even if libunwind is found. See
#4278 for more information.

[1]: https://wiki.freebsd.org/WarnerLosh/UsrLocal

Follows up #4490.
---

https://github.com/tarantool/tarantool/issues/4490
https://github.com/tarantool/tarantool/commits/Totktonada/gh-4490-fix-freebsd-openssl-linking-problems-full-ci

This is more request for review of wording rather then of the code: hope
I verified it carefully enough.

 cmake/BuildLibCURL.cmake | 15 +++++++--------
 cmake/compiler.cmake     |  4 +++-
 cmake/os.cmake           | 27 +++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 9 deletions(-)

diff --git a/cmake/BuildLibCURL.cmake b/cmake/BuildLibCURL.cmake
index 866b3c49e..45f5af23e 100644
--- a/cmake/BuildLibCURL.cmake
+++ b/cmake/BuildLibCURL.cmake
@@ -14,14 +14,10 @@ macro(curl_build)
         message(FATAL_ERROR "Unable to find zlib")
     endif()
 
-    # Set curl option to find OpenSSL library.
-    if ("${OPENSSL_ROOT_DIR}" STREQUAL "")
-        # Linux / FreeBSD.
-        set(LIBCURL_OPENSSL_OPT "--with-ssl")
-    else()
-        # Mac OS.
-        set(LIBCURL_OPENSSL_OPT "--with-ssl=${OPENSSL_ROOT_DIR}")
-    endif()
+    # Use the same OpenSSL library for libcurl as is used for
+    # tarantool itself.
+    get_filename_component(FOUND_OPENSSL_ROOT_DIR ${OPENSSL_INCLUDE_DIR} DIRECTORY)
+    set(LIBCURL_OPENSSL_OPT "--with-ssl=${FOUND_OPENSSL_ROOT_DIR}")
 
     include(ExternalProject)
     ExternalProject_Add(
@@ -35,6 +31,8 @@ macro(curl_build)
         CONFIGURE_COMMAND
             cd <SOURCE_DIR> && ./buildconf &&
             cd <BINARY_DIR> && <SOURCE_DIR>/configure
+                CC=${CMAKE_C_COMPILER}
+                CXX=${CMAKE_CXX_COMPILER}
                 --prefix <INSTALL_DIR>
                 --enable-static
                 --enable-shared
@@ -112,6 +110,7 @@ macro(curl_build)
         set(CURL_LIBRARIES ${CURL_LIBRARIES} rt)
     endif()
 
+    unset(FOUND_OPENSSL_ROOT_DIR)
     unset(LIBCURL_INSTALL_DIR)
     unset(LIBCURL_BINARY_DIR)
     unset(LIBCURL_SOURCE_DIR)
diff --git a/cmake/compiler.cmake b/cmake/compiler.cmake
index 887485c80..c9ad2b092 100644
--- a/cmake/compiler.cmake
+++ b/cmake/compiler.cmake
@@ -128,8 +128,10 @@ else()
 endif()
 find_library(UNWIND_LIBRARY PATH_SUFFIXES system NAMES ${UNWIND_LIB_NAME})
 
+# Disabled backtraces support on FreeBSD by default, because of
+# gh-4278.
 set(ENABLE_BACKTRACE_DEFAULT OFF)
-if (UNWIND_LIBRARY AND HAVE_LIBUNWIND_H)
+if (NOT TARGET_OS_FREEBSD AND UNWIND_LIBRARY AND HAVE_LIBUNWIND_H)
     set(ENABLE_BACKTRACE_DEFAULT ON)
 endif()
 
diff --git a/cmake/os.cmake b/cmake/os.cmake
index ea581108b..fe96ce773 100644
--- a/cmake/os.cmake
+++ b/cmake/os.cmake
@@ -22,6 +22,33 @@ elseif (${CMAKE_SYSTEM_NAME} STREQUAL "kFreeBSD")
 elseif (${CMAKE_SYSTEM_NAME} STREQUAL "FreeBSD")
     set(TARGET_OS_FREEBSD 1)
     find_package_message(PLATFORM "Building for FreeBSD" "${CMAKE_SYSTEM_NAME}")
+
+    # FreeBSD has OpenSSL library installed in /usr as part of a
+    # base system. A user may install OpenSSL from ports / pkg to
+    # /usr/local. It is tricky to use the library from /usr in the
+    # case, because a compilation unit can also depend on
+    # libraries from /usr/local. When -I/usr/local/include is
+    # passed to a compiler it will find openssl/ssl.h from
+    # /usr/local/include first.
+    #
+    # In theory we can create a directory on the build stage and
+    # fill it with symlinks to choosen headers. However this way
+    # does not look as usual way to pick libraries to build
+    # against. I suspect that this is common problem on FreeBSD
+    # and we should wait for some general resolution from FreeBSD
+    # developers rather then work it around.
+    #
+    # Verify that /usr is not set as a directory to pick OpenSSL
+    # library and header files, because it is likely that a user
+    # set it to use the library from a base system, while the
+    # library is also installed into /usr/local.
+    get_filename_component(REAL_OPENSSL_ROOT_DIR "${OPENSSL_ROOT_DIR}"
+                           REALPATH BASE_DIR "${CMAKE_BINARY_DIR}")
+    if ("${REAL_OPENSSL_ROOT_DIR}" STREQUAL "/usr")
+        message(WARNING "Using OPENSSL_ROOT_DIR on FreeBSD to choose base "
+                        "system libraries is not supported")
+    endif()
+    unset(REAL_OPENSSL_ROOT_DIR)
 elseif (${CMAKE_SYSTEM_NAME} STREQUAL "NetBSD")
     set(TARGET_OS_NETBSD 1)
     find_package_message(PLATFORM "Building for NetBSD" "${CMAKE_SYSTEM_NAME}")
-- 
2.22.0