gdb_call_function

Instructions

Implementation Reference

• src/gdb_mcp/server.py:431-446 (registration)

  Tool registration for gdb_call_function - defines the tool name, description, and input schema.

  Tool(
      name="gdb_call_function",
      description=(
          "Call a function in the target process. "
          "WARNING: This is a privileged operation that executes code in the debugged program. "
          "It can call any function accessible in the current context, including: "
          "- Standard library functions: printf, malloc, free, etc. "
          "- Program functions: any function defined in the program "
          "- System calls via wrappers "
          "The function executes with full privileges of the debugged process. "
          "Use with caution as it may have side effects and modify program state. "
          "Examples: 'printf(\"debug: x=%d\\n\", x)', 'my_cleanup_func()', 'strlen(str)'. "
          "Requires session_id parameter (obtained from gdb_start_session)."
      ),
      inputSchema=CallFunctionArgs.model_json_schema(),
  ),

• src/gdb_mcp/server.py:173-179 (schema)

  Input schema for gdb_call_function - defines the session_id and function_call parameters.

  class CallFunctionArgs(BaseModel):
      session_id: int = Field(..., description="Session ID from gdb_start_session")
      function_call: str = Field(
          ...,
          description="Function call expression (e.g., 'printf(\"hello\\n\")' or 'my_func(arg1, arg2)')",
      )

• src/gdb_mcp/server.py:569-571 (handler)

  Handler dispatch for gdb_call_function - parses arguments and delegates to GDBSession.call_function().

  elif name == "gdb_call_function":
      call_args: CallFunctionArgs = CallFunctionArgs(**arguments)
      result = session.call_function(function_call=call_args.function_call)

• src/gdb_mcp/gdb_interface.py:1333-1392 (helper)

  Actual implementation in GDBSession.call_function() - builds the GDB 'call' command and sends it via the MI interpreter.

  def call_function(
      self, function_call: str, timeout_sec: int = DEFAULT_TIMEOUT_SEC
  ) -> dict[str, Any]:
      """
      Call a function in the target process.
  
      This is a privileged operation that executes the GDB 'call' command,
      which invokes a function in the debugged program. This can execute
      arbitrary code in the target process and may have side effects.
  
      WARNING: Use with caution as this can modify program state.
  
      Args:
          function_call: Function call expression (e.g., "printf(\\"hello\\n\\")"
                        or "my_function(arg1, arg2)")
          timeout_sec: Timeout for command execution
  
      Returns:
          Dict with the function's return value or error
      """
      if not self.controller:
          return {"status": "error", "message": "No active GDB session"}
  
      if not self._is_gdb_alive():
          return {
              "status": "error",
              "message": "GDB process has exited - cannot execute call",
          }
  
      # Build the call command
      command = f"call {function_call}"
  
      # Escape for MI command
      escaped_command = command.replace("\\", "\\\\").replace('"', '\\"')
      mi_command = f'-interpreter-exec console "{escaped_command}"'
  
      result = self._send_command_and_wait_for_prompt(mi_command, timeout_sec)
  
      if "error" in result:
          return {
              "status": "error",
              "message": result["error"],
              "function_call": function_call,
          }
  
      if result.get("timed_out"):
          return {
              "status": "error",
              "message": f"Timeout waiting for call to complete after {timeout_sec}s",
              "function_call": function_call,
          }
  
      parsed = self._parse_responses(result.get("command_responses", []))
      console_output = "".join(parsed.get("console", []))
  
      return {
          "status": "success",
          "function_call": function_call,
          "result": console_output.strip() if console_output else "(no return value)",
      }