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signal-slot

MCP GDB Server

by signal-slot

gdb_load

Load a program into GDB for debugging by specifying the session ID and program path, facilitating dynamic analysis and troubleshooting through CLI integration.

Instructions

Load a program into GDB

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
argumentsNoCommand-line arguments for the program (optional)
programYesPath to the program to debug
sessionIdYesGDB session ID

Implementation Reference

  • The handler function that executes the gdb_load tool logic: loads a program into an existing GDB session using the 'file' GDB command and sets program arguments if provided.
    private async handleGdbLoad(args: any) {
      const { sessionId, program, arguments: programArgs = [] } = args;
      
      if (!activeSessions.has(sessionId)) {
        return {
          content: [
            {
              type: 'text',
              text: `No active GDB session with ID: ${sessionId}`
            }
          ],
          isError: true
        };
      }
      
      const session = activeSessions.get(sessionId)!;
      
      try {
        // Normalize path if working directory is set
        const normalizedPath = session.workingDir && !path.isAbsolute(program) 
          ? path.resolve(session.workingDir, program)
          : program;
        
        // Update session target
        session.target = normalizedPath;
        
        // Execute file command to load program
        const loadCommand = `file "${normalizedPath}"`;
        const loadOutput = await this.executeGdbCommand(session, loadCommand);
        
        // Set program arguments if provided
        let argsOutput = '';
        if (programArgs.length > 0) {
          const argsCommand = `set args ${programArgs.join(' ')}`;
          argsOutput = await this.executeGdbCommand(session, argsCommand);
        }
        
        return {
          content: [
            {
              type: 'text',
              text: `Program loaded: ${normalizedPath}\n\nOutput:\n${loadOutput}${argsOutput ? '\n' + argsOutput : ''}`
            }
          ]
        };
      } catch (error) {
        const errorMessage = error instanceof Error ? error.message : String(error);
        return {
          content: [
            {
              type: 'text',
              text: `Failed to load program: ${errorMessage}`
            }
          ],
          isError: true
        };
      }
    }
  • Tool schema definition including name, description, and input schema with required sessionId and program, optional arguments array.
    name: 'gdb_load',
    description: 'Load a program into GDB',
    inputSchema: {
      type: 'object',
      properties: {
        sessionId: {
          type: 'string',
          description: 'GDB session ID'
        },
        program: {
          type: 'string',
          description: 'Path to the program to debug'
        },
        arguments: {
          type: 'array',
          items: {
            type: 'string'
          },
          description: 'Command-line arguments for the program (optional)'
        }
      },
      required: ['sessionId', 'program']
    }
  • src/index.ts:361-362 (registration)
    Registration of the gdb_load tool handler in the CallToolRequestSchema switch statement.
    case 'gdb_load':
      return await this.handleGdbLoad(request.params.arguments);
  • Helper function executeGdbCommand used by gdb_load to send commands to GDB and capture output.
    private executeGdbCommand(session: GdbSession, command: string): Promise<string> {
      return new Promise<string>((resolve, reject) => {
        if (!session.ready) {
          reject(new Error('GDB session is not ready'));
          return;
        }
        
        // Write command to GDB's stdin
        if (session.process.stdin) {
          session.process.stdin.write(command + '\n');
        } else {
          reject(new Error('GDB stdin is not available'));
          return;
        }
        
        let output = '';
        let responseComplete = false;
        
        // Create a one-time event handler for GDB output
        const onLine = (line: string) => {
          output += line + '\n';
          
          // Check if this line indicates the end of the GDB response
          if (line.includes('(gdb)') || line.includes('^done') || line.includes('^error')) {
            responseComplete = true;
            
            // If we've received the complete response, resolve the promise
            if (responseComplete) {
              // Remove the listener to avoid memory leaks
              session.rl.removeListener('line', onLine);
              resolve(output);
            }
          }
        };
        
        // Add the line handler to the readline interface
        session.rl.on('line', onLine);
        
        // Set a timeout to prevent hanging
        const timeout = setTimeout(() => {
          session.rl.removeListener('line', onLine);
          reject(new Error('GDB command timed out'));
        }, 10000); // 10 second timeout
        
        // Handle GDB errors
        const errorHandler = (data: Buffer) => {
          const errorText = data.toString();
          output += `[stderr] ${errorText}\n`;
        };
        
        // Add error handler
        if (session.process.stderr) {
          session.process.stderr.once('data', errorHandler);
        }
        
        // Clean up event handlers when the timeout expires
        timeout.unref();
      });
    }
Behavior2/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the action but lacks details on permissions, side effects (e.g., does it stop execution?), error handling, or output format. This is insufficient for a tool that likely involves program execution and debugging.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is a single, clear sentence with no wasted words, making it highly concise and front-loaded. It efficiently communicates the core purpose without unnecessary elaboration.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the complexity of debugging tools and the lack of annotations and output schema, the description is incomplete. It doesn't cover behavioral aspects like what happens after loading, error scenarios, or how it integrates with other GDB operations, leaving significant gaps for an agent.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the input schema fully documents parameters like 'program' and 'sessionId'. The description adds no additional meaning beyond the schema, such as explaining parameter interactions or constraints, resulting in the baseline score.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description 'Load a program into GDB' clearly states the action (load) and target (program into GDB), making the purpose understandable. However, it doesn't differentiate from sibling tools like 'gdb_start' or 'gdb_attach', which might have overlapping or related functionality, preventing a perfect score.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description provides no guidance on when to use this tool versus alternatives. For example, it doesn't clarify if this is for initial loading vs. attaching to a running process, or how it relates to tools like 'gdb_start' or 'gdb_attach', leaving the agent without context for selection.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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