> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# C++ Multi-line Comment
A multi-line comment in C++ is a lexical construct that instructs the compiler to ignore a sequence of characters spanning one or more lines. During the lexical analysis phase, the C++ preprocessor replaces the entire comment block with a single whitespace character, effectively stripping it from the translation unit before compilation.
## Syntax
Multi-line comments are enclosed by a starting `/*` token and a terminating `*/` token. Every character between these two delimiters is ignored by the compiler.
```cpp theme={"dark"}
/*
This text is ignored by the compiler.
It can span an arbitrary number of lines.
*/
```
## Lexical Rules and Behavior
**1. Inline Placement**
Because multi-line comments have explicit termination tokens, they can be placed inline within a single statement. They are valid anywhere a whitespace character is valid, provided they do not split a single language token (such as an identifier or a keyword).
```cpp theme={"dark"}
int x = 10 /* initialization */ + 20;
```
**2. No Nesting**
Standard C++ does not support nested multi-line comments. The lexical scanner operates sequentially and terminates the comment block at the very first `*/` sequence it encounters, regardless of how many `/*` sequences preceded it. Attempting to nest these comments leaves trailing text exposed to the compiler.
```cpp theme={"dark"}
/* Outer comment starts
/* Inner comment starts */
// The comment block is now closed.
// The following characters would cause a syntax error if not commented out:
// */
```
**3. Interaction with Single-line Comments**
The C++ tokenizer processes comment initiators based on whichever appears first. If a multi-line comment initiator (`/*`) appears after a single-line comment initiator (`//`) on the same line, it is treated as standard text within the single-line comment and does not begin a multi-line comment block. Conversely, a `//` sequence inside a `/* ... */` block has no special meaning and is ignored.
```cpp theme={"dark"}
// This is a single-line comment containing /*
int y = 5; // The multi-line comment was never started.
/*
This is a multi-line comment.
// This does not start a single-line comment.
*/
```
**4. String Literal Exception**
The compiler's tokenizer prioritizes string and character literals. If the `/*` or `*/` sequences appear within double quotes (`" "`) or single quotes (`' '`), they are evaluated as standard character data rather than comment delimiters.
```cpp theme={"dark"}
const char* str = "This is not a /* comment */";
```
**5. Line Splicing**
If a multi-line comment delimiter is split using a line-continuation character (a backslash `\` immediately followed by a newline), the preprocessor will splice the lines together before tokenization, successfully forming the comment delimiter.
```cpp theme={"dark"}
/\
*
This is a valid multi-line comment due to line splicing.
*\
/
```
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