server: Revert "Report backtraces in codemodel response"

The backtrace information is very repetitive and hugely increases the
size of the codemodel object.  We need to remove it until an alternative
representation can be developed.  Revert commit v3.10.0-rc1~393^2
(server: Report backtraces in codemodel response, 2017-06-20), except
for the protocol version number (because it indicates other new things).

Unfortunately this is incompatible with clients that expect the
"crossReferences" field in targets.  However, the regression in memory
usage is quite serious, especially on large projects, and therefore
breaks even older clients that do not use backtraces.  Since the
"crossReferences" field was only provided by one release (3.10.0), it is
simplest to revert it outright for 3.10.1.

Fixes: #17502

4 files changed, 13 insertions, 95 deletions

diff --git a/Help/manual/cmake-server.7.rst b/Help/manual/cmake-server.7.rst
index c56e5a7..50a90ee 100644
--- a/Help/manual/cmake-server.7.rst
+++ b/Help/manual/cmake-server.7.rst
@@ -506,9 +506,6 @@ Each target object can have the following keys:
   with the sysroot path.
 "fileGroups"
   contains the source files making up the target.
-"crossReferences"
-  contains the location of the target in the corresponding CMakeLists.txt
-  file and the locations of the related statements like "target_link_libraries"
 
 FileGroups are used to group sources using similar settings together.
 
@@ -534,16 +531,6 @@ Each fileGroup object may contain the following keys:
 All file paths in the fileGroup are either absolute or relative to the
 sourceDirectory of the target.
 
-CrossReferences object is used to report the location of the target (including
-the entire call stack if the target is defined in a function) and the related
-"target_link_libraries", "target_include_directories", "target_compile_definitions"
-and "target_compile_options" statements.
-
-See the example below for details on the internal format of the "crossReferences" object.
-Line numbers stated in the "backtrace" entries are 1-based. The last entry of a backtrace
-is a special entry with missing "line" and "name" fields that specifies the initial
-CMakeLists.txt file.
-
 Example::
 
   [== "CMake Server" ==[
@@ -580,34 +567,7 @@ CMake will reply::
                 "linkerLanguage": "C",
                 "name": "cmForm",
                 "sourceDirectory": "/home/code/src/cmake/Source/CursesDialog/form",
-                "type": "STATIC_LIBRARY",
-                "crossReferences": {
-                   "backtrace": [
-                      {
-                         "line": 7,
-                         "name": "add_executable",
-                         "path": "C:/full/path/CMakeLists.txt"
-                      },
-                      {
-                         "path": "c:/full/path/CMakeLists.txt"
-                      }
-                   ],
-                   "relatedStatements": [
-                      {
-                         "backtrace": [
-                            {
-                               "line": 8,
-                               "name": "target_link_libraries",
-                               "path": "c:/full/path/CMakeLists.txt"
-                            },
-                            {
-                               "path": "c:/full/path/CMakeLists.txt"
-                            }
-                         ],
-                         "type": "target_link_libraries"
-                      }
-                   ]
-                 }
+                "type": "STATIC_LIBRARY"
               }
             ]
           },
diff --git a/Help/release/3.10.rst b/Help/release/3.10.rst
index 35fe602..6a19dbf 100644
--- a/Help/release/3.10.rst
+++ b/Help/release/3.10.rst
@@ -255,3 +255,15 @@ Other Changes
   incompatible with the old behavior, it is expected that behavior
   under typical use cases with properly-quoted command-lines has
   not changed.
+
+Updates
+=======
+
+Changes made since CMake 3.10.0 include the following.
+
+3.10.1
+------
+
+* The :manual:`cmake-server(7)` ``codemodel`` response ``crossReferences``
+  field added by 3.10.0 has been dropped due to excessive memory usage.
+  Another approach will be needed to provide backtrace information.
diff --git a/Source/cmServerDictionary.h b/Source/cmServerDictionary.h
index 405ff6b..e6a7ae6 100644
--- a/Source/cmServerDictionary.h
+++ b/Source/cmServerDictionary.h
@@ -89,11 +89,6 @@ static const std::string kWARN_UNUSED_KEY = "warnUnused";
 static const std::string kWATCHED_DIRECTORIES_KEY = "watchedDirectories";
 static const std::string kWATCHED_FILES_KEY = "watchedFiles";
 
-static const std::string kTARGET_CROSS_REFERENCES_KEY = "crossReferences";
-static const std::string kLINE_NUMBER_KEY = "line";
-static const std::string kBACKTRACE_KEY = "backtrace";
-static const std::string kRELATED_STATEMENTS_KEY = "relatedStatements";
-
 static const std::string kSTART_MAGIC = "[== \"CMake Server\" ==[";
 static const std::string kEND_MAGIC = "]== \"CMake Server\" ==]";
 
diff --git a/Source/cmServerProtocol.cxx b/Source/cmServerProtocol.cxx
index e835b7a..13b18c2 100644
--- a/Source/cmServerProtocol.cxx
+++ b/Source/cmServerProtocol.cxx
@@ -9,7 +9,6 @@
 #include "cmGeneratorTarget.h"
 #include "cmGlobalGenerator.h"
 #include "cmLinkLineComputer.h"
-#include "cmListFileCache.h"
 #include "cmLocalGenerator.h"
 #include "cmMakefile.h"
 #include "cmServer.h"
@@ -20,7 +19,6 @@
 #include "cmStateSnapshot.h"
 #include "cmStateTypes.h"
 #include "cmSystemTools.h"
-#include "cmTarget.h"
 #include "cm_uv.h"
 #include "cmake.h"
 
@@ -732,37 +730,6 @@ static Json::Value DumpSourceFilesList(
   return result;
 }
 
-static Json::Value DumpBacktrace(const cmListFileBacktrace& backtrace)
-{
-  Json::Value result = Json::arrayValue;
-
-  cmListFileBacktrace backtraceCopy = backtrace;
-  while (!backtraceCopy.Top().FilePath.empty()) {
-    Json::Value entry = Json::objectValue;
-    entry[kPATH_KEY] = backtraceCopy.Top().FilePath;
-    if (backtraceCopy.Top().Line) {
-      entry[kLINE_NUMBER_KEY] = static_cast<int>(backtraceCopy.Top().Line);
-    }
-    if (!backtraceCopy.Top().Name.empty()) {
-      entry[kNAME_KEY] = backtraceCopy.Top().Name;
-    }
-    result.append(entry);
-    backtraceCopy = backtraceCopy.Pop();
-  }
-  return result;
-}
-
-static void DumpBacktraceRange(Json::Value& result, const std::string& type,
-                               cmBacktraceRange range)
-{
-  for (auto const& bt : range) {
-    Json::Value obj = Json::objectValue;
-    obj[kTYPE_KEY] = type;
-    obj[kBACKTRACE_KEY] = DumpBacktrace(bt);
-    result.append(obj);
-  }
-}
-
 static Json::Value DumpTarget(cmGeneratorTarget* target,
                               const std::string& config)
 {
@@ -797,22 +764,6 @@ static Json::Value DumpTarget(cmGeneratorTarget* target,
 
   result[kFULL_NAME_KEY] = target->GetFullName(config);
 
-  Json::Value crossRefs = Json::objectValue;
-  crossRefs[kBACKTRACE_KEY] = DumpBacktrace(target->Target->GetBacktrace());
-
-  Json::Value statements = Json::arrayValue;
-  DumpBacktraceRange(statements, "target_compile_definitions",
-                     target->Target->GetCompileDefinitionsBacktraces());
-  DumpBacktraceRange(statements, "target_include_directories",
-                     target->Target->GetIncludeDirectoriesBacktraces());
-  DumpBacktraceRange(statements, "target_compile_options",
-                     target->Target->GetCompileOptionsBacktraces());
-  DumpBacktraceRange(statements, "target_link_libraries",
-                     target->Target->GetLinkImplementationBacktraces());
-
-  crossRefs[kRELATED_STATEMENTS_KEY] = std::move(statements);
-  result[kTARGET_CROSS_REFERENCES_KEY] = std::move(crossRefs);
-
   if (target->HaveWellDefinedOutputFiles()) {
     Json::Value artifacts = Json::arrayValue;
     artifacts.append(