fix compilation error with latest llvm 8.0 trunk (#1976)

In llvm/clang 8 trunk, the following commits
  https://reviews.llvm.org/rL339384
  https://reviews.llvm.org/rL339385
  https://reviews.llvm.org/rL339386
renames getLocStart to getBeginLoc, and getLocEnd to getEndLoc.
This caused bcc compilation error with llvm/clang 8.
To avoid proliferation of #define's based on LLVM version numbers
and similar logic for many different types,
this patch fixed the issues by define macros in common
frontend_action_common.h where macro definition is multi-versioned
based on llvm version. The macro itself is used in
{b,tp}_frontend_action.cc.

clang 8 also introduced a new library dependency
  libclangAnalysis.a depends on libclangASTMatchers.a
This patch fixed this issue as well.
Signed-off-by: Yonghong Song <yhs@fb.com>

CMakeLists.txt

@@ -45,6 +45,7 @@ find_library(libclangParse NAMES clangParse HINTS ${CLANG_SEARCH})
 find_library(libclangRewrite NAMES clangRewrite HINTS ${CLANG_SEARCH})
 find_library(libclangSema NAMES clangSema HINTS ${CLANG_SEARCH})
 find_library(libclangSerialization NAMES clangSerialization HINTS ${CLANG_SEARCH})
+find_library(libclangASTMatchers NAMES clangASTMatchers HINTS ${CLANG_SEARCH})
 if(libclangBasic STREQUAL "libclangBasic-NOTFOUND")
   message(FATAL_ERROR "Unable to find clang libraries")
 endif()

cmake/clang_libs.cmake

@@ -23,7 +23,13 @@ endif()
 set(clang_libs
   ${libclangFrontend}
   ${libclangSerialization}
-  ${libclangDriver}
+  ${libclangDriver})
+
+if (${LLVM_PACKAGE_VERSION} VERSION_EQUAL 8 OR ${LLVM_PACKAGE_VERSION} VERSION_GREATER 8)
+  list(APPEND clang_libs ${libclangASTMatchers})
+endif()
+
+list(APPEND clang_libs
   ${libclangParse}
   ${libclangSema}
   ${libclangCodeGen}

src/cc/frontends/clang/frontend_action_common.h

+/*
+ * Copyright (c) 2018 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#if LLVM_MAJOR_VERSION >= 8
+#define GET_BEGINLOC(E)  ((E)->getBeginLoc())
+#define GET_ENDLOC(E)  ((E)->getEndLoc())
+#else
+#define GET_BEGINLOC(E)  ((E)->getLocStart())
+#define GET_ENDLOC(E)    ((E)->getLocEnd())
+#endif

src/cc/frontends/clang/tp_frontend_action.cc

@@ -28,6 +28,7 @@
 #include <clang/Frontend/MultiplexConsumer.h>
 #include <clang/Rewrite/Core/Rewriter.h>
 
+#include "frontend_action_common.h"
 #include "tp_frontend_action.h"
 
 namespace ebpf {
@@ -209,11 +210,11 @@ bool TracepointTypeVisitor::VisitFunctionDecl(FunctionDecl *D) {
         string tp_cat, tp_evt;
         if (_is_tracepoint_struct_type(type_name, tp_cat, tp_evt)) {
           string tp_struct = GenerateTracepointStruct(
-              D->getLocStart(), tp_cat, tp_evt);
+              GET_BEGINLOC(D), tp_cat, tp_evt);
           // Get the actual function declaration point (the macro instantiation
           // point if using the TRACEPOINT_PROBE macro instead of the macro
           // declaration point in bpf_helpers.h).
-          auto insert_loc = D->getLocStart();
+          auto insert_loc = GET_BEGINLOC(D);
           insert_loc = rewriter_.getSourceMgr().getFileLoc(insert_loc);
           rewriter_.InsertText(insert_loc, tp_struct);
         }