Microsoft/monaco-editor

C++ line continuation mark (\) should be ignored everywhere

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#1184 opened on Nov 14, 2018

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feature-requestgrammarshelp wantedopen for PR

Description

monaco-editor version: 0.15.1 Browser: Chrome (maybe others) OS: Windows

In C/C++ \ is used as line continuation mark so defining macros in multi-line is possible:

#define MACRO do { \
} while(false);

It is also possible to change a single line comment to multi-line with \:

// Multi \
   Line \
   Comment

As you see in above snippet, Github syntax highlighter accept this syntax in comments and colorize line 2 and 3 as comments, but Monaco does not:

image

This is somehow strange that the VSCode highlights it correctly but Monaco does not. image

Contributor guide

Tech stack
cpptypescript
Domain
frontend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
TextMate grammar basicsMonaco editor tokenization
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
The issue is that C++ line continuation backslash is not ignored in comments and strings. The fix likely requires modifying the C++ TextMate grammar file used by Monaco (e.g., `src/basic languages/cpp/cpp.tmLanguage.ts`). The grammar needs to handle the backslash as a line continuation character in macros and single line comments. Look at how VSCode handles it (since VSCode uses Monaco but has correct behavior) and port that logic. The change is localized to the grammar definition.