CXX-2796 Restore external polyfill library and stdlib support (#1086)

* Add BSONCXX_USE_POLY_IMPLS to configuration

* Restore stdlib selection for make_unique, string_view, and optional

* CXX-641 fix usage of common flags in abidiff-test.sh

* Disable tests for external library polyfills

* Add changelog entry for ENABLE_BSONCXX_USE_POLY_IMPLS

* CXX-2797 Document ENABLE_BSONCXX_POLY_USE_IMPLS and deprecate external polyfill libraries

* CXX-2746 Ignore detail namespaces in abi-compliance-check-test.sh

* Add deprecation warnings for external polyfill library configurations

* Avoid including external symbols in v_noabi abidiff reports

* Ignore warnings for symbols unreferenced by debug info in abidiff

* Fix scoped_bson_t ambiguous overloads for views and values

* Add missing include in catch.hh

* Fix missing std::in_place equivalent for Boost before 1.63

* Improve quality of error messages for type trait assertions

* Relax trait equality assertions for stdlib implementations

* Declare BUILD_TESTING as a CMake option variable

* Fix CCACHE_BASEDIR for Windows distros

* Add missing macro guards for BSONCXX_POLY_USE_STD

* Revert reintroduction of documentation for experimental stdlib polyfill

* Move common polyfill selection documentation into separate page

Author: eramongodb

.evergreen/abi-compliance-check-test.sh

@@ -22,20 +22,13 @@ command -V abi-compliance-checker >/dev/null
 
 mkdir cxx-abi cxx-noabi
 
-cat >cxx-abi/old.xml <<DOC
+# Generate XML descriptors with sections used by both old and new tests.
+if true; then
+  cat >old.xml <<DOC
 <version>
   ${old_ver:?}
 </version>
 
-<headers>
-  ../install/old/include/bsoncxx/
-  ../install/old/include/mongocxx/
-</headers>
-
-<skip_headers>
-  /v_noabi/
-</skip_headers>
-
 <libs>
   ../install/old/lib
 </libs>
@@ -44,26 +37,13 @@ cat >cxx-abi/old.xml <<DOC
   ../install/old/include/
 </add_include_paths>
 
-<skip_including>
-  bsoncxx/enums/
-  /config/
-</skip_including>
 DOC
 
-cat >cxx-abi/new.xml <<DOC
+  cat >new.xml <<DOC
 <version>
   ${new_ver:?}
 </version>
 
-<headers>
-  ../install/new/include/mongocxx/
-  ../install/new/include/bsoncxx/
-</headers>
-
-<skip_headers>
-  /v_noabi/
-</skip_headers>
-
 <libs>
   ../install/new/lib
 </libs>
@@ -72,59 +52,67 @@ cat >cxx-abi/new.xml <<DOC
   ../install/new/include/
 </add_include_paths>
 
+DOC
+
+  {
+    cat <<DOC
 <skip_including>
-  bsoncxx/enums/
-  /config/
+  bsoncxx/v_noabi/bsoncxx/enums/
+  bsoncxx/v_noabi/bsoncxx/config/
 </skip_including>
+
+<skip_namespaces>
+  bsoncxx::detail
+  bsoncxx::v_noabi::detail
+  bsoncxx::v_noabi::stdx::detail
+</skip_namespaces>
+
 DOC
+  } | tee -a old.xml new.xml >/dev/null
 
-cat >cxx-noabi/old.xml <<DOC
-<version>
-  ${old_ver:?}
-</version>
+  cat old.xml | tee cxx-abi/old.xml cxx-noabi/old.xml >/dev/null
+  cat new.xml | tee cxx-abi/new.xml cxx-noabi/new.xml >/dev/null
+  rm old.xml new.xml
+fi
 
+# Append sections specific to each ABI test.
+if true; then
+  cat >>cxx-abi/old.xml <<DOC
+<headers>
+  ../install/old/include/bsoncxx/
+  ../install/old/include/mongocxx/
+</headers>
+
+<skip_headers>
+  /v_noabi/
+</skip_headers>
+DOC
+
+  cat >>cxx-noabi/old.xml <<DOC
 <headers>
   ../install/old/include/bsoncxx/v_noabi
   ../install/old/include/mongocxx/v_noabi
 </headers>
+DOC
 
-<libs>
-  ../install/old/lib
-</libs>
-
-<add_include_paths>
-  ../install/old/include/
-</add_include_paths>
+  cat >>cxx-abi/new.xml <<DOC
+<headers>
+  ../install/new/include/mongocxx/
+  ../install/new/include/bsoncxx/
+</headers>
 
-<skip_including>
-  bsoncxx/enums/
-  /config/
-</skip_including>
+<skip_headers>
+  /v_noabi/
+</skip_headers>
 DOC
 
-cat >cxx-noabi/new.xml <<DOC
-<version>
-  ${new_ver:?}
-</version>
-
+  cat >>cxx-noabi/new.xml <<DOC
 <headers>
   ../install/new/include/bsoncxx/v_noabi
   ../install/new/include/mongocxx/v_noabi
 </headers>
-
-<libs>
-  ../install/new/lib
-</libs>
-
-<add_include_paths>
-  ../install/new/include/
-</add_include_paths>
-
-<skip_including>
-  bsoncxx/enums/
-  /config/
-</skip_including>
 DOC
+fi
 
 # Allow task to upload the HTML report despite failed status.
 echo "Generating stable ABI report..."

.evergreen/abidiff-test.sh

@@ -10,15 +10,15 @@ export PATH
 PATH="${working_dir:?}/install/bin:${PATH:-}"
 
 declare -a common_flags
-flags=(
+common_flags=(
   --headers-dir1 install/old/include
   --headers-dir2 install/new/include
-  --non-reachable-types
-  --fail-no-debug-info
+  --fail-no-debug-info      # Ensure debug info is present for our libs.
+  --no-unreferenced-symbols # Not interested in symbols not owned by our libs.
 )
 
-declare -a abi_flags=("${common_flags[@]}" --suppressions cxx-abi/abignore)
-declare -a noabi_flags=("${common_flags[@]}" --suppressions cxx-noabi/abignore)
+declare -a abi_flags=("${common_flags[@]:?}" --suppressions cxx-abi/abignore)
+declare -a noabi_flags=("${common_flags[@]:?}" --suppressions cxx-noabi/abignore)
 
 command -V abidiff >/dev/null
 
@@ -37,18 +37,24 @@ DOC
 
 cat >cxx-noabi/abignore <<DOC
 [suppress_type]
-name_regexp = ^(bsoncxx|mongocxx)::v[[:digit:]]+::
+name_not_regexp = ^(bsoncxx|mongocxx)::v_noabi::
 
 [suppress_function]
-name_regexp = ^(bsoncxx|mongocxx)::v[[:digit:]]+::
+name_not_regexp = ^(bsoncxx|mongocxx)::v_noabi::
 
 [suppress_variable]
-name_regexp = ^(bsoncxx|mongocxx)::v[[:digit:]]+::
+name_not_regexp = ^(bsoncxx|mongocxx)::v_noabi::
 DOC
 
+# Ensure files have content even when abidiff produces no output.
+echo "---" >>cxx-abi/bsoncxx.txt
+echo "---" >>cxx-abi/mongocxx.txt
+echo "---" >>cxx-noabi/bsoncxx.txt
+echo "---" >>cxx-noabi/mongocxx.txt
+
 # Allow task to upload the diff reports despite failed status.
 echo "Comparing stable ABI for bsoncxx..."
-if ! abidiff "${abi_flags[@]}" install/old/lib/libbsoncxx.so install/new/lib/libbsoncxx.so &>cxx-abi/bsoncxx.txt; then
+if ! abidiff "${abi_flags[@]:?}" install/old/lib/libbsoncxx.so install/new/lib/libbsoncxx.so >>cxx-abi/bsoncxx.txt; then
   declare status
   status='{"status":"failed", "type":"test", "should_continue":true, "desc":"abidiff returned an error for bsoncxx (stable)"}'
   curl -sS -d "${status:?}" -H "Content-Type: application/json" -X POST localhost:2285/task_status || true
@@ -57,23 +63,23 @@ echo "Comparing stable ABI for bsoncxx... done."
 
 # Allow task to upload the diff reports despite failed status.
 echo "Comparing stable ABI for mongocxx..."
-if ! abidiff "${abi_flags[@]}" install/old/lib/libmongocxx.so install/new/lib/libmongocxx.so &>cxx-abi/mongocxx.txt; then
+if ! abidiff "${abi_flags[@]:?}" install/old/lib/libmongocxx.so install/new/lib/libmongocxx.so >>cxx-abi/mongocxx.txt; then
   declare status
   status='{"status":"failed", "type":"test", "should_continue":true, "desc":"abidiff returned an error for mongocxx (stable)"}'
   curl -sS -d "${status:?}" -H "Content-Type: application/json" -X POST localhost:2285/task_status || true
 fi
 echo "Comparing stable ABI for mongocxx... done."
 
 echo "Comparing unstable ABI for bsoncxx..."
-abidiff "${noabi_flags[@]}" install/old/lib/libbsoncxx.so install/new/lib/libbsoncxx.so &>cxx-noabi/bsoncxx.txt || true
+abidiff "${noabi_flags[@]:?}" install/old/lib/libbsoncxx.so install/new/lib/libbsoncxx.so >>cxx-noabi/bsoncxx.txt || true
 echo "Comparing unstable ABI for bsoncxx... done."
 
 echo "Comparing unstable ABI for mongocxx..."
-abidiff "${noabi_flags[@]}" install/old/lib/libmongocxx.so install/new/lib/libmongocxx.so &>cxx-noabi/mongocxx.txt || true
+abidiff "${noabi_flags[@]:?}" install/old/lib/libmongocxx.so install/new/lib/libmongocxx.so >>cxx-noabi/mongocxx.txt || true
 echo "Comparing unstable ABI for mongocxx... done."
 
 # Ensure files have content even when abidiff produces no output.
-printf "\n" >>cxx-abi/bsoncxx.txt
-printf "\n" >>cxx-abi/mongocxx.txt
-printf "\n" >>cxx-noabi/bsoncxx.txt
-printf "\n" >>cxx-noabi/mongocxx.txt
+echo "---" >>cxx-abi/bsoncxx.txt
+echo "---" >>cxx-abi/mongocxx.txt
+echo "---" >>cxx-noabi/bsoncxx.txt
+echo "---" >>cxx-noabi/mongocxx.txt

.evergreen/compile.sh

@@ -71,11 +71,11 @@ if command -V ccache 2>/dev/null; then
 
   # Allow reuse of ccache compilation results between different build directories.
   export CCACHE_BASEDIR CCACHE_NOHASHDIR
-  CCACHE_BASEDIR="$(pwd)"
-  CCACHE_NOHASHDIR=1
-  # Allow reuse of ccache compilation results between different build directories.
-  export CCACHE_BASEDIR CCACHE_NOHASHDIR
-  CCACHE_BASEDIR="$(pwd)"
+  if [[ "${OSTYPE:?}" == "cygwin" ]]; then
+    CCACHE_BASEDIR="$(cygpath -aw "$(pwd)")"
+  else
+    CCACHE_BASEDIR="$(pwd)"
+  fi
   CCACHE_NOHASHDIR=1
 fi
 

.mci.yml

@@ -952,7 +952,11 @@ tasks:
 
               # Allow reuse of ccache compilation results between different build directories.
               export CCACHE_BASEDIR CCACHE_NOHASHDIR
-              CCACHE_BASEDIR="$(pwd)"
+              if [[ "${OSTYPE:?}" == "cygwin" ]]; then
+                CCACHE_BASEDIR="$(cygpath -aw "$(pwd)")"
+              else
+                CCACHE_BASEDIR="$(pwd)"
+              fi
               CCACHE_NOHASHDIR=1
             fi
             command -v "$cmake_binary"

CHANGELOG.md

@@ -14,6 +14,8 @@ Changes prior to 3.9.0 are documented as [release notes on GitHub](https://githu
 - Forward headers providing non-defining declarations of bsoncxx and mongocxx class types.
   - Note: user-defined forward declarations of any library entity has not been, and is still not, supported.
     To obtain the declaration or definition of a library entity, always include the corresponding header.
+- The CMake option `ENABLE_BSONCXX_USE_POLY_IMPLS` (OFF by default) allows selecting bsoncxx implementations of C++17 polyfills by default when no polyfill library is requested.
+- The CMake option `BSONCXX_POLY_USE_IMPLS` (OFF by default) allows selecting bsoncxx implementations of C++17 polyfills instead of external libraries or the C++ standard library.
 
 ### Changed
 

CMakeLists.txt

@@ -20,9 +20,7 @@ endif()
 
 project(MONGO_CXX_DRIVER LANGUAGES CXX)
 
-if(NOT DEFINED BUILD_TESTING)
-    set(BUILD_TESTING OFF) # Set this to OFF by default
-endif()
+option(BUILD_TESTING "Include test targets in the \"all\" target")
 
 if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU")
     if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "4.8.2")
@@ -157,6 +155,9 @@ option(BUILD_SHARED_LIBS_WITH_STATIC_MONGOC
     OFF
 )
 
+# Allow the user to opt into using bsoncxx implementations for C++17 polyfills by default.
+option(ENABLE_BSONCXX_POLY_USE_IMPLS "Enable using bsoncxx implementations of C++17 polyfills for pre-C++17 configurations by default" OFF)
+
 if(DEFINED CACHE{ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES} AND NOT MSVC)
     message(WARNING "ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES is an MSVC-only option and will be ignored by the current configuration")
     unset(ENABLE_ABI_TAG_IN_LIBRARY_FILENAMES CACHE)
@@ -475,6 +476,10 @@ if(NOT(TARGET dist OR TARGET distcheck))
         list(APPEND polyfill_flags "-DBSONCXX_POLY_USE_BOOST=${BSONCXX_POLY_USE_BOOST}")
     endif()
 
+    if(NOT "${BSONCXX_POLY_USE_IMPLS}" STREQUAL "")
+        list(APPEND polyfill_flags "-DBSONCXX_POLY_USE_IMPLS=${BSONCXX_POLY_USE_IMPLS}")
+    endif()
+
     if(NOT "${BSONCXX_POLY_USE_STD}" STREQUAL "")
         list(APPEND polyfill_flags "-DBSONCXX_POLY_USE_STD=${BSONCXX_POLY_USE_STD}")
     endif()

cmake/BsoncxxUtil.cmake

@@ -62,7 +62,7 @@ function(bsoncxx_add_library TARGET OUTPUT_NAME LINK_TYPE)
                 set(polyfill "m")
             elseif(BSONCXX_POLY_USE_BOOST)
                 set(polyfill "b")
-            elseif(0) # CXX-2796: reserved for bsoncxx implementations as polyfill.
+            elseif(BSONCXX_POLY_USE_IMPLS)
                 set(polyfill "i")
             elseif(BSONCXX_POLY_USE_STD)
                 set(polyfill "s")