[Lldb-commits] [lldb] [lldb-dap] Provide `declarationLocation` for variables (PR #102928)

Adrian Vogelsgesang via lldb-commits lldb-commits at lists.llvm.org
Fri Aug 16 05:25:09 PDT 2024


https://github.com/vogelsgesang updated https://github.com/llvm/llvm-project/pull/102928

>From 079def868f0216f31b78469f63034db5b350e250 Mon Sep 17 00:00:00 2001
From: Adrian Vogelsgesang <avogelsgesang at salesforce.com>
Date: Sat, 10 Aug 2024 23:59:55 +0000
Subject: [PATCH] [lldb-dap] Implement declaration locations

This commit implements support for the "declaration location" recently
added by microsoft/debug-adapter-protocol#494 to the debug adapter
protocol.

For the `declarationLocationReference` we need a variable ID similar to
the the `variablesReference`. I decided to simply reuse the
`variablesReference` here and renamed `Variables::expandable_variables`
and friends accordingly. Given that almost all variables have a
declaration location, we now assign those variable ids to all variables.

While `declarationLocationReference` effectively supersedes
`$__lldb_extensions.declaration`, I did not remove this extension, yet,
since I assume that there are some closed-source extensions which rely
on it.

I tested this against VS-Code Insiders. However, VS-Code Insiders
currently only supports `valueLoctionReference` and not
`declarationLocationReference`, yet. Locally, I hence tried to publish
the declaration locations as value locations. However, it seems that
VS-Code still has issues with correctly resolving file paths, as
reported in https://github.com/microsoft/vscode/pull/225546#issuecomment-2292428591
---
 .../test/tools/lldb-dap/dap_server.py         |  11 ++
 .../API/tools/lldb-dap/locations/Makefile     |   3 +
 .../lldb-dap/locations/TestDAP_locations.py   |  40 +++++
 lldb/test/API/tools/lldb-dap/locations/main.c |   5 +
 lldb/tools/lldb-dap/DAP.cpp                   |  17 +-
 lldb/tools/lldb-dap/DAP.h                     |  10 +-
 lldb/tools/lldb-dap/JSONUtils.cpp             | 125 ++++++++-------
 lldb/tools/lldb-dap/JSONUtils.h               |  31 ++--
 lldb/tools/lldb-dap/lldb-dap.cpp              | 146 +++++++++++++++---
 9 files changed, 286 insertions(+), 102 deletions(-)
 create mode 100644 lldb/test/API/tools/lldb-dap/locations/Makefile
 create mode 100644 lldb/test/API/tools/lldb-dap/locations/TestDAP_locations.py
 create mode 100644 lldb/test/API/tools/lldb-dap/locations/main.c

diff --git a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
index a324af57b61df3..9879a34ed2020c 100644
--- a/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
+++ b/lldb/packages/Python/lldbsuite/test/tools/lldb-dap/dap_server.py
@@ -1079,6 +1079,17 @@ def request_setVariable(self, containingVarRef, name, value, id=None):
         }
         return self.send_recv(command_dict)
 
+    def request_locations(self, locationReference):
+        args_dict = {
+            "locationReference": locationReference,
+        }
+        command_dict = {
+            "command": "locations",
+            "type": "request",
+            "arguments": args_dict,
+        }
+        return self.send_recv(command_dict)
+
     def request_testGetTargetBreakpoints(self):
         """A request packet used in the LLDB test suite to get all currently
         set breakpoint infos for all breakpoints currently set in the
diff --git a/lldb/test/API/tools/lldb-dap/locations/Makefile b/lldb/test/API/tools/lldb-dap/locations/Makefile
new file mode 100644
index 00000000000000..10495940055b63
--- /dev/null
+++ b/lldb/test/API/tools/lldb-dap/locations/Makefile
@@ -0,0 +1,3 @@
+C_SOURCES := main.c
+
+include Makefile.rules
diff --git a/lldb/test/API/tools/lldb-dap/locations/TestDAP_locations.py b/lldb/test/API/tools/lldb-dap/locations/TestDAP_locations.py
new file mode 100644
index 00000000000000..76d938d3908492
--- /dev/null
+++ b/lldb/test/API/tools/lldb-dap/locations/TestDAP_locations.py
@@ -0,0 +1,40 @@
+"""
+Test lldb-dap locations request
+"""
+
+
+import dap_server
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+import lldbdap_testcase
+import os
+
+
+class TestDAP_locations(lldbdap_testcase.DAPTestCaseBase):
+    @skipIfWindows
+    def test_locations(self):
+        """
+        Tests the 'locations' request.
+        """
+        program = self.getBuildArtifact("a.out")
+        self.build_and_launch(program)
+        source = "main.c"
+        self.source_path = os.path.join(os.getcwd(), source)
+        self.set_source_breakpoints(
+            source,
+            [line_number(source, "// BREAK HERE")],
+        )
+        self.continue_to_next_stop()
+
+        locals = {l["name"]: l for l in self.dap_server.get_local_variables()}
+
+        # var1 has a declarationLocation but no valueLocation
+        self.assertIn("declarationLocationReference", locals["var1"].keys())
+        self.assertNotIn("valueLocationReference", locals["var1"].keys())
+        loc_var1 = self.dap_server.request_locations(
+            locals["var1"]["declarationLocationReference"]
+        )
+        self.assertTrue(loc_var1["success"])
+        self.assertTrue(loc_var1["body"]["source"]["path"].endswith("main.c"))
+        self.assertEqual(loc_var1["body"]["line"], 2)
diff --git a/lldb/test/API/tools/lldb-dap/locations/main.c b/lldb/test/API/tools/lldb-dap/locations/main.c
new file mode 100644
index 00000000000000..6a8c86d00cb562
--- /dev/null
+++ b/lldb/test/API/tools/lldb-dap/locations/main.c
@@ -0,0 +1,5 @@
+int main(void) {
+  int var1 = 1;
+  // BREAK HERE
+  return 0;
+}
diff --git a/lldb/tools/lldb-dap/DAP.cpp b/lldb/tools/lldb-dap/DAP.cpp
index c3c70e9d739846..a773c2df28ed25 100644
--- a/lldb/tools/lldb-dap/DAP.cpp
+++ b/lldb/tools/lldb-dap/DAP.cpp
@@ -813,7 +813,7 @@ void Variables::Clear() {
   locals.Clear();
   globals.Clear();
   registers.Clear();
-  expandable_variables.clear();
+  referenced_variables.clear();
 }
 
 int64_t Variables::GetNewVariableReference(bool is_permanent) {
@@ -828,24 +828,23 @@ bool Variables::IsPermanentVariableReference(int64_t var_ref) {
 
 lldb::SBValue Variables::GetVariable(int64_t var_ref) const {
   if (IsPermanentVariableReference(var_ref)) {
-    auto pos = expandable_permanent_variables.find(var_ref);
-    if (pos != expandable_permanent_variables.end())
+    auto pos = referenced_permanent_variables.find(var_ref);
+    if (pos != referenced_permanent_variables.end())
       return pos->second;
   } else {
-    auto pos = expandable_variables.find(var_ref);
-    if (pos != expandable_variables.end())
+    auto pos = referenced_variables.find(var_ref);
+    if (pos != referenced_variables.end())
       return pos->second;
   }
   return lldb::SBValue();
 }
 
-int64_t Variables::InsertExpandableVariable(lldb::SBValue variable,
-                                            bool is_permanent) {
+int64_t Variables::InsertVariable(lldb::SBValue variable, bool is_permanent) {
   int64_t var_ref = GetNewVariableReference(is_permanent);
   if (is_permanent)
-    expandable_permanent_variables.insert(std::make_pair(var_ref, variable));
+    referenced_permanent_variables.insert(std::make_pair(var_ref, variable));
   else
-    expandable_variables.insert(std::make_pair(var_ref, variable));
+    referenced_variables.insert(std::make_pair(var_ref, variable));
   return var_ref;
 }
 
diff --git a/lldb/tools/lldb-dap/DAP.h b/lldb/tools/lldb-dap/DAP.h
index 57562a14983519..848e69145da4f6 100644
--- a/lldb/tools/lldb-dap/DAP.h
+++ b/lldb/tools/lldb-dap/DAP.h
@@ -104,12 +104,12 @@ struct Variables {
   int64_t next_temporary_var_ref{VARREF_FIRST_VAR_IDX};
   int64_t next_permanent_var_ref{PermanentVariableStartIndex};
 
-  /// Expandable variables that are alive in this stop state.
+  /// Variables that are alive in this stop state.
   /// Will be cleared when debuggee resumes.
-  llvm::DenseMap<int64_t, lldb::SBValue> expandable_variables;
-  /// Expandable variables that persist across entire debug session.
+  llvm::DenseMap<int64_t, lldb::SBValue> referenced_variables;
+  /// Variables that persist across entire debug session.
   /// These are the variables evaluated from debug console REPL.
-  llvm::DenseMap<int64_t, lldb::SBValue> expandable_permanent_variables;
+  llvm::DenseMap<int64_t, lldb::SBValue> referenced_permanent_variables;
 
   /// Check if \p var_ref points to a variable that should persist for the
   /// entire duration of the debug session, e.g. repl expandable variables
@@ -127,7 +127,7 @@ struct Variables {
 
   /// Insert a new \p variable.
   /// \return variableReference assigned to this expandable variable.
-  int64_t InsertExpandableVariable(lldb::SBValue variable, bool is_permanent);
+  int64_t InsertVariable(lldb::SBValue variable, bool is_permanent);
 
   /// Clear all scope variables and non-permanent expandable variables.
   void Clear();
diff --git a/lldb/tools/lldb-dap/JSONUtils.cpp b/lldb/tools/lldb-dap/JSONUtils.cpp
index a8b85f55939e17..5738a3034990c1 100644
--- a/lldb/tools/lldb-dap/JSONUtils.cpp
+++ b/lldb/tools/lldb-dap/JSONUtils.cpp
@@ -614,9 +614,8 @@ CreateExceptionBreakpointFilter(const ExceptionBreakpoint &bp) {
 //     }
 //   }
 // }
-llvm::json::Value CreateSource(lldb::SBLineEntry &line_entry) {
+llvm::json::Value CreateSource(const lldb::SBFileSpec &file) {
   llvm::json::Object object;
-  lldb::SBFileSpec file = line_entry.GetFileSpec();
   if (file.IsValid()) {
     const char *name = file.GetFilename();
     if (name)
@@ -630,6 +629,10 @@ llvm::json::Value CreateSource(lldb::SBLineEntry &line_entry) {
   return llvm::json::Value(std::move(object));
 }
 
+llvm::json::Value CreateSource(const lldb::SBLineEntry &line_entry) {
+  return CreateSource(line_entry.GetFileSpec());
+}
+
 llvm::json::Value CreateSource(llvm::StringRef source_path) {
   llvm::json::Object source;
   llvm::StringRef name = llvm::sys::path::filename(source_path);
@@ -1143,65 +1146,75 @@ std::string VariableDescription::GetResult(llvm::StringRef context) {
 //       "description": "The number of indexed child variables. The client
 //                       can use this optional information to present the
 //                       children in a paged UI and fetch them in chunks."
-//     }
-//
+//     },
+//     "declarationLocationReference": {
+//       "type": "integer",
+//       "description": "A reference that allows the client to request the
+//                       location where the variable is declared. This should be
+//                       present only if the adapter is likely to be able to
+//                       resolve the location.\n\nThis reference shares the same
+//                       lifetime as the `variablesReference`. See 'Lifetime of
+//                       Object References' in the Overview section for
+//                       details."
+//     },
 //
 //     "$__lldb_extensions": {
 //       "description": "Unofficial extensions to the protocol",
 //       "properties": {
 //         "declaration": {
-//         "type": "object",
-//         "description": "The source location where the variable was declared.
-//                         This value won't be present if no declaration is
-//                         available.",
-//         "properties": {
-//           "path": {
-//             "type": "string",
-//             "description": "The source file path where the variable was
-//                            declared."
-//           },
-//           "line": {
-//             "type": "number",
-//             "description": "The 1-indexed source line where the variable was
-//                             declared."
-//           },
-//           "column": {
-//             "type": "number",
-//             "description": "The 1-indexed source column where the variable
-//                             was declared."
+//           "type": "object",
+//           "description": "The source location where the variable was
+//                           declared. This value won't be present if no
+//                           declaration is available.
+//                           Superseded by `declarationLocationReference`",
+//           "properties": {
+//             "path": {
+//               "type": "string",
+//               "description": "The source file path where the variable was
+//                              declared."
+//             },
+//             "line": {
+//               "type": "number",
+//               "description": "The 1-indexed source line where the variable
+//                               was declared."
+//             },
+//             "column": {
+//               "type": "number",
+//               "description": "The 1-indexed source column where the variable
+//                               was declared."
+//             }
 //           }
+//         },
+//         "value": {
+//           "type": "string",
+//           "description": "The internal value of the variable as returned by
+//                            This is effectively SBValue.GetValue(). The other
+//                            `value` entry in the top-level variable response
+//                            is, on the other hand, just a display string for
+//                            the variable."
+//         },
+//         "summary": {
+//           "type": "string",
+//           "description": "The summary string of the variable. This is
+//                           effectively SBValue.GetSummary()."
+//         },
+//         "autoSummary": {
+//           "type": "string",
+//           "description": "The auto generated summary if using
+//                           `enableAutoVariableSummaries`."
+//         },
+//         "error": {
+//           "type": "string",
+//           "description": "An error message generated if LLDB couldn't inspect
+//                           the variable."
 //         }
-//       },
-//       "value":
-//         "type": "string",
-//         "description": "The internal value of the variable as returned by
-//                         This is effectively SBValue.GetValue(). The other
-//                         `value` entry in the top-level variable response is,
-//                          on the other hand, just a display string for the
-//                          variable."
-//       },
-//       "summary":
-//         "type": "string",
-//         "description": "The summary string of the variable. This is
-//                         effectively SBValue.GetSummary()."
-//       },
-//       "autoSummary":
-//         "type": "string",
-//         "description": "The auto generated summary if using
-//                         `enableAutoVariableSummaries`."
-//       },
-//       "error":
-//         "type": "string",
-//         "description": "An error message generated if LLDB couldn't inspect
-//                         the variable."
 //       }
 //     }
 //   },
 //   "required": [ "name", "value", "variablesReference" ]
 // }
-llvm::json::Value CreateVariable(lldb::SBValue v, int64_t variablesReference,
-                                 int64_t varID, bool format_hex,
-                                 bool is_name_duplicated,
+llvm::json::Value CreateVariable(lldb::SBValue v, int64_t var_ref,
+                                 bool format_hex, bool is_name_duplicated,
                                  std::optional<std::string> custom_name) {
   VariableDescription desc(v, format_hex, is_name_duplicated, custom_name);
   llvm::json::Object object;
@@ -1246,12 +1259,18 @@ llvm::json::Value CreateVariable(lldb::SBValue v, int64_t variablesReference,
     }
   }
   EmplaceSafeString(object, "type", desc.display_type_name);
-  if (varID != INT64_MAX)
-    object.try_emplace("id", varID);
+
+  // A unique variable identifier to help in properly identifying variables with
+  // the same name. This is an extension to the VS protocol.
+  object.try_emplace("id", var_ref);
+
   if (v.MightHaveChildren())
-    object.try_emplace("variablesReference", variablesReference);
+    object.try_emplace("variablesReference", var_ref);
   else
-    object.try_emplace("variablesReference", (int64_t)0);
+    object.try_emplace("variablesReference", 0);
+
+  if (v.GetDeclaration().IsValid())
+    object.try_emplace("declarationLocationReference", var_ref);
 
   object.try_emplace("$__lldb_extensions", desc.GetVariableExtensionsJSON());
   return llvm::json::Value(std::move(object));
diff --git a/lldb/tools/lldb-dap/JSONUtils.h b/lldb/tools/lldb-dap/JSONUtils.h
index 1515f5ba2e5f4d..0a88dd269bfbdf 100644
--- a/lldb/tools/lldb-dap/JSONUtils.h
+++ b/lldb/tools/lldb-dap/JSONUtils.h
@@ -282,6 +282,16 @@ llvm::json::Value CreateScope(const llvm::StringRef name,
                               int64_t variablesReference,
                               int64_t namedVariables, bool expensive);
 
+/// Create a "Source" JSON object as described in the debug adaptor definition.
+///
+/// \param[in] file
+///     The SBFileSpec to use when populating out the "Source" object
+///
+/// \return
+///     A "Source" JSON object that follows the formal JSON
+///     definition outlined by Microsoft.
+llvm::json::Value CreateSource(const lldb::SBFileSpec &file);
+
 /// Create a "Source" JSON object as described in the debug adaptor definition.
 ///
 /// \param[in] line_entry
@@ -289,9 +299,9 @@ llvm::json::Value CreateScope(const llvm::StringRef name,
 ///     object
 ///
 /// \return
-///     A "Source" JSON object with that follows the formal JSON
+///     A "Source" JSON object that follows the formal JSON
 ///     definition outlined by Microsoft.
-llvm::json::Value CreateSource(lldb::SBLineEntry &line_entry);
+llvm::json::Value CreateSource(const lldb::SBLineEntry &line_entry);
 
 /// Create a "Source" object for a given source path.
 ///
@@ -433,15 +443,10 @@ struct VariableDescription {
 ///     The LLDB value to use when populating out the "Variable"
 ///     object.
 ///
-/// \param[in] variablesReference
-///     The variable reference. Zero if this value isn't structured
-///     and has no children, non-zero if it does have children and
-///     might be asked to expand itself.
-///
-/// \param[in] varID
-///     A unique variable identifier to help in properly identifying
-///     variables with the same name. This is an extension to the
-///     VS protocol.
+/// \param[in] var_ref
+///     The variable reference. Used to identify the value, e.g.
+///     in the `variablesReference` or `declarationLocationReference`
+///     properties.
 ///
 /// \param[in] format_hex
 ///     It set to true the variable will be formatted as hex in
@@ -462,8 +467,8 @@ struct VariableDescription {
 /// \return
 ///     A "Variable" JSON object with that follows the formal JSON
 ///     definition outlined by Microsoft.
-llvm::json::Value CreateVariable(lldb::SBValue v, int64_t variablesReference,
-                                 int64_t varID, bool format_hex,
+llvm::json::Value CreateVariable(lldb::SBValue v, int64_t var_ref,
+                                 bool format_hex,
                                  bool is_name_duplicated = false,
                                  std::optional<std::string> custom_name = {});
 
diff --git a/lldb/tools/lldb-dap/lldb-dap.cpp b/lldb/tools/lldb-dap/lldb-dap.cpp
index ea84f31aec3a6c..ccf1ea61f9973e 100644
--- a/lldb/tools/lldb-dap/lldb-dap.cpp
+++ b/lldb/tools/lldb-dap/lldb-dap.cpp
@@ -8,6 +8,7 @@
 
 #include "DAP.h"
 #include "Watchpoint.h"
+#include "lldb/API/SBDeclaration.h"
 #include "lldb/API/SBMemoryRegionInfo.h"
 
 #include <cassert>
@@ -1405,7 +1406,7 @@ void request_evaluate(const llvm::json::Object &request) {
       EmplaceSafeString(body, "result", desc.GetResult(context));
       EmplaceSafeString(body, "type", desc.display_type_name);
       if (value.MightHaveChildren()) {
-        auto variableReference = g_dap.variables.InsertExpandableVariable(
+        auto variableReference = g_dap.variables.InsertVariable(
             value, /*is_permanent=*/context == "repl");
         body.try_emplace("variablesReference", variableReference);
       } else {
@@ -3598,8 +3599,8 @@ void request_setVariable(const llvm::json::Object &request) {
       // is_permanent is false because debug console does not support
       // setVariable request.
       if (variable.MightHaveChildren())
-        newVariablesReference = g_dap.variables.InsertExpandableVariable(
-            variable, /*is_permanent=*/false);
+        newVariablesReference =
+            g_dap.variables.InsertVariable(variable, /*is_permanent=*/false);
 
       body.try_emplace("variablesReference", newVariablesReference);
     } else {
@@ -3770,13 +3771,10 @@ void request_variables(const llvm::json::Object &request) {
       if (!variable.IsValid())
         break;
 
-      int64_t var_ref = 0;
-      if (variable.MightHaveChildren() || variable.IsSynthetic()) {
-        var_ref = g_dap.variables.InsertExpandableVariable(
-            variable, /*is_permanent=*/false);
-      }
+      int64_t var_ref =
+          g_dap.variables.InsertVariable(variable, /*is_permanent=*/false);
       variables.emplace_back(CreateVariable(
-          variable, var_ref, var_ref != 0 ? var_ref : UINT64_MAX, hex,
+          variable, var_ref, hex,
           variable_name_counts[GetNonNullVariableName(variable)] > 1));
     }
   } else {
@@ -3788,19 +3786,11 @@ void request_variables(const llvm::json::Object &request) {
                           std::optional<std::string> custom_name = {}) {
         if (!child.IsValid())
           return;
-        if (child.MightHaveChildren()) {
-          auto is_permanent =
-              g_dap.variables.IsPermanentVariableReference(variablesReference);
-          auto childVariablesReferences =
-              g_dap.variables.InsertExpandableVariable(child, is_permanent);
-          variables.emplace_back(CreateVariable(
-              child, childVariablesReferences, childVariablesReferences, hex,
-              /*is_name_duplicated=*/false, custom_name));
-        } else {
-          variables.emplace_back(CreateVariable(child, 0, INT64_MAX, hex,
-                                                /*is_name_duplicated=*/false,
-                                                custom_name));
-        }
+        bool is_permanent =
+            g_dap.variables.IsPermanentVariableReference(variablesReference);
+        int64_t var_ref = g_dap.variables.InsertVariable(child, is_permanent);
+        variables.emplace_back(CreateVariable(
+            child, var_ref, hex, /*is_name_duplicated=*/false, custom_name));
       };
       const int64_t num_children = variable.GetNumChildren();
       int64_t end_idx = start + ((count == 0) ? num_children : count);
@@ -3823,6 +3813,117 @@ void request_variables(const llvm::json::Object &request) {
   g_dap.SendJSON(llvm::json::Value(std::move(response)));
 }
 
+// "LocationsRequest": {
+//   "allOf": [ { "$ref": "#/definitions/Request" }, {
+//     "type": "object",
+//     "description": "Looks up information about a location reference
+//                     previously returned by the debug adapter.",
+//     "properties": {
+//       "command": {
+//         "type": "string",
+//         "enum": [ "locations" ]
+//       },
+//       "arguments": {
+//         "$ref": "#/definitions/LocationsArguments"
+//       }
+//     },
+//     "required": [ "command", "arguments" ]
+//   }]
+// },
+// "LocationsArguments": {
+//   "type": "object",
+//   "description": "Arguments for `locations` request.",
+//   "properties": {
+//     "locationReference": {
+//       "type": "integer",
+//       "description": "Location reference to resolve."
+//     }
+//   },
+//   "required": [ "locationReference" ]
+// },
+// "LocationsResponse": {
+//   "allOf": [ { "$ref": "#/definitions/Response" }, {
+//     "type": "object",
+//     "description": "Response to `locations` request.",
+//     "properties": {
+//       "body": {
+//         "type": "object",
+//         "properties": {
+//           "source": {
+//             "$ref": "#/definitions/Source",
+//             "description": "The source containing the location; either
+//                             `source.path` or `source.sourceReference` must be
+//                             specified."
+//           },
+//           "line": {
+//             "type": "integer",
+//             "description": "The line number of the location. The client
+//                             capability `linesStartAt1` determines whether it
+//                             is 0- or 1-based."
+//           },
+//           "column": {
+//             "type": "integer",
+//             "description": "Position of the location within the `line`. It is
+//                             measured in UTF-16 code units and the client
+//                             capability `columnsStartAt1` determines whether
+//                             it is 0- or 1-based. If no column is given, the
+//                             first position in the start line is assumed."
+//           },
+//           "endLine": {
+//             "type": "integer",
+//             "description": "End line of the location, present if the location
+//                             refers to a range.  The client capability
+//                             `linesStartAt1` determines whether it is 0- or
+//                             1-based."
+//           },
+//           "endColumn": {
+//             "type": "integer",
+//             "description": "End position of the location within `endLine`,
+//                             present if the location refers to a range. It is
+//                             measured in UTF-16 code units and the client
+//                             capability `columnsStartAt1` determines whether
+//                             it is 0- or 1-based."
+//           }
+//         },
+//         "required": [ "source", "line" ]
+//       }
+//     }
+//   }]
+// },
+void request_locations(const llvm::json::Object &request) {
+  llvm::json::Object response;
+  FillResponse(request, response);
+  auto arguments = request.getObject("arguments");
+
+  uint64_t reference_id = GetUnsigned(arguments, "locationReference", 0);
+  lldb::SBValue variable = g_dap.variables.GetVariable(reference_id);
+  if (!variable.IsValid()) {
+    response["success"] = false;
+    response["message"] = "Invalid variable reference";
+    g_dap.SendJSON(llvm::json::Value(std::move(response)));
+    return;
+  }
+
+  // Get the declaration location
+  lldb::SBDeclaration decl = variable.GetDeclaration();
+  if (!decl.IsValid()) {
+    response["success"] = false;
+    response["message"] = "No declaration location available";
+    g_dap.SendJSON(llvm::json::Value(std::move(response)));
+    return;
+  }
+
+  llvm::json::Object body;
+  body.try_emplace("source", CreateSource(decl.GetFileSpec()));
+  if (int line = decl.GetLine())
+    body.try_emplace("line", line);
+  if (int column = decl.GetColumn())
+    body.try_emplace("column", column);
+
+  response.try_emplace("body", std::move(body));
+  g_dap.SendJSON(llvm::json::Value(std::move(response)));
+}
+
 // "DisassembleRequest": {
 //   "allOf": [ { "$ref": "#/definitions/Request" }, {
 //     "type": "object",
@@ -4077,6 +4178,7 @@ void RegisterRequestCallbacks() {
   g_dap.RegisterRequestCallback("stepOut", request_stepOut);
   g_dap.RegisterRequestCallback("threads", request_threads);
   g_dap.RegisterRequestCallback("variables", request_variables);
+  g_dap.RegisterRequestCallback("locations", request_locations);
   g_dap.RegisterRequestCallback("disassemble", request_disassemble);
   // Custom requests
   g_dap.RegisterRequestCallback("compileUnits", request_compileUnits);



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