Allow overriding assert() functionality in libgpcodegen in DEBUG mode

 * Support assert overriding in Linux and OSX.
 * Add checks in CMakelists.txt in case LLVM libraries already override
   assert()
Signed-off-by: NNikos Armenatzoglou <nikos.armenatzoglou@gmail.com>

src/backend/codegen/CMakeLists.txt

@@ -61,19 +61,24 @@ if (COMPILER_HAS_WNO_C99_EXTENSIONS)
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-deprecated-register")
 endif()
 
-# Turn on the CODEGEN_DEBUG flag if this is a debug build.
+macro (ADD_DEBUG_COMPILE_DEFINITION SYMBOL)
 if (CMAKE_MAJOR_VERSION GREATER 2)
   cmake_policy(SET CMP0043 NEW)
   set_property(
     DIRECTORY
-    APPEND PROPERTY COMPILE_DEFINITIONS $<$<CONFIG:Debug>:CODEGEN_DEBUG>
+    APPEND PROPERTY COMPILE_DEFINITIONS $<$<CONFIG:Debug>:${SYMBOL}>
   )
 else()
   set_property(
     DIRECTORY
-    APPEND PROPERTY COMPILE_DEFINITIONS_DEBUG CODEGEN_DEBUG
+    APPEND PROPERTY COMPILE_DEFINITIONS_DEBUG ${SYMBOL}
   )
 endif()
+endmacro()
+
+# Turn on the CODEGEN_DEBUG flag if this is a debug build.
+ADD_DEBUG_COMPILE_DEFINITION(CODEGEN_DEBUG)
+
 
 # Check for POSIX I/O syscalls needed by TemporaryFile.
 include(CheckCXXSymbolExists)
@@ -136,6 +141,7 @@ add_library(gpcodegen SHARED
             utils/clang_compiler.cc
             utils/codegen_utils.cc
             utils/gp_codegen_utils.cc
+            utils/gp_assert.cc
 
             codegen_interface.cc
             codegen_manager.cc
@@ -160,8 +166,8 @@ else()
 endif()
 
 #  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.
+#  references in a dynamic library. Instead, it should wait till it's loaded
+#  by the postgres binary.
 if(APPLE)
   set(WL_UNDEFINED_DYNLOOKUP "-Wl,-undefined -Wl,dynamic_lookup")
 else()
@@ -185,6 +191,51 @@ else()
   target_link_libraries(gpcodegen ${WL_START_GROUP} ${codegen_llvm_libs} ${WL_END_GROUP})
 endif()
 
+# This macro checks to see if the given C symbol is defined in the given LIBRARY. A library with
+# an appropriate name is searched for in the LIBPATH. VARIABLE is set to true if the symbol is
+# found defined as a type in (T in the output of nm) in the library, or set false otherwise.
+macro(CHECK_SYMBOL_DEFINED LIBRARY CSYMBOL LIBPATH VARIABLE)
+	find_library(LIBLOCATION ${LIBRARY} ${LIBPATH})
+	if(LIBLOCATION STREQUAL "LIBLOCATION-NOTFOUND")
+		message(FATAL_ERROR "${LIBRARY} not found in ${LIBPATH}.")
+	endif()
+	find_program(NM_BIN "nm")
+	execute_process(COMMAND ${NM_BIN} ${LIBLOCATION}
+                  COMMAND grep "T"  # Symbol is defined
+                  COMMAND grep ${CSYMBOL}
+                  RESULT_VARIABLE RETURN_CODE
+                  OUTPUT_QUIET)
+  if(${RETURN_CODE} EQUAL 0) # One or more lines were selected
+		set(VARIABLE true)
+  elseif(${RETURN_CODE} EQUAL 1) # No lines were selected.
+		set(VARIABLE false)
+	else()
+		message(FATAL_ERROR "Attempted to determine it ${CSYMBOL} is defined in ${LIBLOCATION} "
+					  "but the execution failed. Return code = ${RETURN_CODE}")
+  endif()
+endmacro()
+
+if(APPLE)
+  set(ASSERT_FUNCTION_TO_OVERRIDE "__assert_rtn")
+elseif(UNIX)
+  set(ASSERT_FUNCTION_TO_OVERRIDE "__assert_fail")
+endif()
+
+if(CMAKE_BUILD_TYPE STREQUAL Debug)
+  # Since we want to override assert handling in GPDB, we need to make sure
+  # that LLVM and Clang libraries we depend on haven't done that already
+  # If they do, we simply report a WARNING, and skip assert overriding in GPDB.
+  CHECK_SYMBOL_DEFINED(LLVMSupport ${ASSERT_FUNCTION_TO_OVERRIDE} ${LLVM_LIBRARY_DIRS} LLVM_ASSERT_REDEFINED)
+  if (LLVM_ASSERT_REDEFINED)
+    message(WARNING
+            "Found ${ASSERT_FUNCTION_TO_OVERRIDE} redefined in LLVM libraries. "
+            "Disabling GPDB codegen assert handling! "
+            "To enable this, rebuild LLVM libraries with -DLLVM_ENABLE_CRASH_OVERRIDES=off.")
+  else()
+    ADD_DEBUG_COMPILE_DEFINITION(CODEGEN_GPDB_ASSERT_HANDLING)
+  endif()
+endif()
+
 get_filename_component(full_install_name_dir "${CMAKE_INSTALL_PREFIX}/lib" ABSOLUTE)
 set_target_properties(
     gpcodegen PROPERTIES

src/backend/codegen/utils/gp_assert.cc

+//---------------------------------------------------------------------------
+//  Greenplum Database
+//  Copyright (C) 2016 Pivotal Software, Inc.
+//
+//  @filename:
+//    gp_assert.cc
+//
+//  @doc:
+//    Implementation of lower level assert methods to override C++ assert()
+//    functionality to pass any errors to GPDB.
+//
+//---------------------------------------------------------------------------
+
+#ifdef CODEGEN_GPDB_ASSERT_HANDLING
+extern "C" {
+#include <utils/elog.h>
+
+// Overload assert handling from LLVM, and pass any error messages to GPDB.
+// LLVM has a custom implementation of __assert_rtn, only compiled
+// on OSX. To prevent naming conflicts when building GPDB, LLVM should
+// be built with -DLLVM_ENABLE_CRASH_OVERRIDES=off
+//
+// (Refer http://lists.llvm.org/pipermail/llvm-commits/Week-of-Mon-20130826/186121.html)
+#ifdef __APPLE__
+void __assert_rtn(const char *func,
+                  const char *file,
+                  int line,
+                  const char *expr) {
+#elif __linux__
+void __assert_fail(const char * expr,
+                   const char * file,
+                   unsigned int line,
+                   const char * func) {
+#endif
+
+  if (!func) {
+    func = "";
+  }
+
+  errstart(ERROR, file, line, func, TEXTDOMAIN);
+  errfinish(errcode(ERRCODE_INTERNAL_ERROR),
+            errmsg("C++ assertion failed: \"%s\"",
+            expr));
+
+  // Normal execution beyond this point is unsafe
+}
+}
+#endif  // CODEGEN_GPDB_ASSERT_HANDLING