%.* is not a supported debug specifier

[mmomtchev]

• Version: v14.13.1
• Platform: Linux
• Subsystem: http2

What steps will reproduce the bug?

(example from #35475)
NODE_DEBUG_NATIVE=HTTP2SESSION node

const http2 = require('http2');
const tls = require('tls');
const stream = require('stream');

const options = {
    ALPNProtocols: ['h2'],
    host: 'nghttp2.org',
    servername: 'nghttp2.org',
    port: 443
};

const socket = tls.connect(options, async () => {
    console.log('TLS Connected!');

    const proxy = new stream.Duplex({
        read(...args) {
            const x = socket.read();
            console.log('read', JSON.stringify(x));
            if (x !== null)
            this.push(x);
        },

        final(...args) {
            socket.end(...args);
        },

        write(...args) {
            socket.write(...args);
        },

        destroy(...args) {
            socket.destroy(...args);
        }
    });

    await new Promise(resolve => setTimeout(resolve, 2000));

    const session = http2.connect('https://nghttp2.org', {
        createConnection: () => socket
    });

    session.once('remoteSettings', () => {
        console.log('HTTP2 Received remote settings!');
    });

    session.once('connect', () => {
        console.log('HTTP2 Connected!');
    });

});

Additional information

master is not affected

[mmomtchev]

node/src/debug_utils-inl.h

Line 80 in 7f25fe8

switch (*p) {

doesn't seem to support %.* as a format specifier, yet there are a few examples in the code? @addaleax?
Currently the % eats the length specifier then the second argument triggers the CHECK_NOT_NULL

[addaleax]

@mmomtchev Yeah, length specifiers make sense for a printf that is mainly intended to handle C strings, but it’s not important for a type-aware C++ variant like the one that we have. I think it would be just fine here to replace Debug(session, "Error '%.*s'", len, message); with Debug(session, "Error '%s'", std::string(message, len));.

[mmomtchev]

Yes, in fact, there are 3 different sprintfs used through out the code: this one, from debug_utils-inl.h, the V8 one and the OS-provided one - and all the other examples are for the other two which support it