Organize codegen source files and unit tests

* Move these into one gpcodegen dynamic library, leaving on
  codegen_wrapper.cc in SUBSYS.o
* Convert simple-gtests to cmockery_gtests since libgpcodegen may have
  references to Postgres symbols

Minor changes

src/backend/codegen/CMakeLists.txt

@@ -131,11 +131,26 @@ find_package(Clang REQUIRED)
 include_directories(${CLANG_INCLUDE_DIRS})
 
 # Core codegen library.
+# This builds all the codegen-related C++ sources into one library
 add_library(gpcodegen SHARED
             utils/clang_compiler.cc
             utils/codegen_utils.cc
             utils/gp_codegen_utils.cc
+
+            codegen_interface.cc
+            codegen_manager.cc
+            const_expr_tree_generator.cc
+            exec_variable_list_codegen.cc
+            slot_getattr_codegen.cc
+            exec_eval_expr_codegen.cc
+            expr_tree_generator.cc
+            op_expr_tree_generator.cc
+            pg_date_func_generator.cc
+            var_expr_tree_generator.cc
+            advance_aggregates_codegen.cc
+
             ${codegen_tmpfile_sources})
+
 if(APPLE)
   set(WL_START_GROUP "")
   set(WL_END_GROUP "")
@@ -144,7 +159,16 @@ else()
   set(WL_END_GROUP "-Wl,--end-group")
 endif()
 
-target_link_libraries(gpcodegen ${WL_START_GROUP} ${CLANG_LIBRARIES} ${WL_END_GROUP})
+#  By default, the Darwin linker throws an error if there are any undefined
+#  references in a dynamic library. Instead, it should wait till it's linked
+#  back with the postgres binary.
+if(APPLE)
+  set(WL_UNDEFINED_DYNLOOKUP "-Wl,-undefined -Wl,dynamic_lookup")
+else()
+  set(WL_UNDEFINED_DYNLOOKUP "")
+endif()
+
+target_link_libraries(gpcodegen ${WL_START_GROUP} ${CLANG_LIBRARIES} ${WL_END_GROUP} ${WL_UNDEFINED_DYNLOOKUP})
 if (MONOLITHIC_LLVM_LIBRARY)
   target_link_libraries(gpcodegen ${LLVM_MONOLITHIC_LIBRARIES})
 else()
@@ -167,27 +191,12 @@ set_target_properties(
     INSTALL_NAME_DIR ${full_install_name_dir}
     MACOSX_RPATH ON)
 
-set(GPCODEGEN_SRC
-    codegen_interface.cc
-    codegen_manager.cc
-    codegen_wrapper.cc
-    const_expr_tree_generator.cc
-    exec_variable_list_codegen.cc
-    slot_getattr_codegen.cc
-    exec_eval_expr_codegen.cc
-    expr_tree_generator.cc
-    op_expr_tree_generator.cc
-    pg_date_func_generator.cc
-    var_expr_tree_generator.cc
-    advance_aggregates_codegen.cc
-)
-
 # Integrate with GPDB build system. 
-# Here we compile all the GPDB code generators, and link them incrementally
-# with the gpcodegen shared library to create a binary SUBSYS.o as expected by
-# GPDB make system. We invoke the linker with -nostdlib since we don't really
-# want to create a full executable.
-add_executable(SUBSYS.o ${GPCODEGEN_SRC})
+# Here we compile the GPDB wrappers and link it with the gpcodegen shared
+# library to create a binary SUBSYS.o as expected by GPDB make system.  We
+# invoke the linker with -nostdlib since we don't really want to create a full
+# executable.
+add_executable(SUBSYS.o codegen_wrapper.cc)
 set_target_properties(SUBSYS.o
     PROPERTIES
     LINK_FLAGS "-Wl,-r -nostdlib")
@@ -210,9 +219,9 @@ SET(GTEST_DIR ../../../gpAux/extensions/gtest)
 add_subdirectory(${GTEST_DIR} ${CMAKE_BINARY_DIR}/gtest EXCLUDE_FROM_ALL)
 enable_testing()
 
-SET (TEST_LIB_INC_DIRECTORIES
-${TOP_SRC_DIR}/src/test/unit/cmockery
-${GTEST_DIR}/include)
+set(TEST_LIB_INC_DIRECTORIES
+    ${TOP_SRC_DIR}/src/test/unit/cmockery
+    ${GTEST_DIR}/include)
 			
 function(prepend_path var prefix)
    SET(listVar "")
@@ -222,17 +231,6 @@ function(prepend_path var prefix)
    SET(${var} "${listVar}" PARENT_SCOPE)
 endfunction(prepend_path)
 
-function(add_simple_gtest TEST_NAME TEST_SRC)
-    add_executable(${TEST_NAME} EXCLUDE_FROM_ALL ${TEST_SRC})
-	target_include_directories(${TEST_NAME} PUBLIC ${TEST_LIB_INC_DIRECTORIES})
-    target_link_libraries(${TEST_NAME} gpcodegen gtest)
-    add_test(${TEST_NAME} ${TEST_NAME})
-    add_dependencies(check ${TEST_NAME})
-endfunction(add_simple_gtest)
-
-add_simple_gtest(clang_compiler_unittest.t tests/clang_compiler_unittest.cc)
-add_simple_gtest(codegen_utils_unittest.t tests/codegen_utils_unittest.cc)
-add_simple_gtest(instance_method_wrappers_unittest.t tests/instance_method_wrappers_unittest.cc)
 
 # Usage add_cmock_gtest ${TEST_NAME} ${TEST_SOURCES} ${MOCK_DIR}/hello_mock.o ${MOCK_DIR}/world_mock.o)
 function(add_cmockery_gtest TEST_NAME TEST_SOURCES)
@@ -257,7 +255,7 @@ function(add_cmockery_gtest TEST_NAME TEST_SOURCES)
 
     add_executable(${TEST_NAME} EXCLUDE_FROM_ALL 
         ${TEST_SOURCES}
-        ${GPCODEGEN_SRC}
+        codegen_wrapper.cc
         ${FILES_TO_LINK} 
         ${MOCK_OBJS} 
         ${CMOCKERY_OBJS}
@@ -310,14 +308,25 @@ if(EXISTS ${TXT_OBJFILE})
 endif()
 
 # Add CMockery tests
+# All tests must be linked with postgres, even if they don't need the cmockery
+# framework  since libgpcodegen may now have references to postgres symbols.
+#
+# Usage add_cmock_gtest ${TEST_NAME} ${TEST_SOURCES} ${MOCK_DIR}/hello_mock.o ${MOCK_DIR}/world_mock.o)
 if(EXISTS ${TXT_OBJFILE})
     add_cmockery_gtest(codegen_framework_unittest.t 
         tests/codegen_framework_unittest.cc
-        ${MOCK_DIR}/backend/postmaster/postmaster_mock.o
     )
     add_cmockery_gtest(codegen_pg_func_generator_unittest.t 
         tests/codegen_pg_func_generator_unittest.cc
-        ${MOCK_DIR}/backend/postmaster/postmaster_mock.o
+    )
+    add_cmockery_gtest(clang_compiler_unittest.t
+        tests/clang_compiler_unittest.cc
+    )
+    add_cmockery_gtest(instance_method_wrappers_unittest.t
+        tests/instance_method_wrappers_unittest.cc
+    )
+    add_cmockery_gtest(codegen_utils_unittest.t
+        tests/codegen_utils_unittest.cc
     )
 endif()