Is there a difference between;

int main(){
return 0;
}

and

int main(){return 0;}

and

int main(){
return
0;
}

They will all likely compile to same executable. How does the C/C compiler treat the extra spaces and newlines, and if there is a difference between how newlines are treated differently than spaces in C code?

Also, how about tabs? What's the significance of using tabs instead of spaces in code, if there is any?

CodePudding user response：

Any sequence of 1 whitespace symbol (space/line-break/tab/...) is equivalent to a single space.

Exceptions:

• Whitespace is preserved in string literals. They can't contain line-breaks, except C raw literals (R"(...)"). The same applies to file names in #include.
• Single-line comments (//) are terminated with line-breaks only.
• Preprocessor directives (starting with #) are terminated with line-breaks only.
• \ followed by a line-break removes both, allowing multi-line // comments, preprocessor directrives, and string literals.

Also, whitespace symbols are ignored if there is punctuation (anything except letters, numbers, and _) to the left and/or to the right of it. E.g. 1 2 and 1 2 are the same, but return a; and returna; are not.

Exceptions:

• Whitespace is not ignored inside string literals, obviously. Nor in #include file names.

• Operators consisting of >1 punctuation symbols can't be separated, e.g. cout < < 1 is illegal. The same applies to things like // and /* */.

• A space between punctuation might be necessary to prevent it from coalescing into a single operator. Examples:

  • a is different from a.
  • a b is equivalent to a b, but not to a b.
  • Pre-C 11, closing two template argument lists in a row required a space: std::vector<std::vector<int> >.

• When defining a function-like macro, the space is not allowed before the opening parenthesis (adding it turns it into an object-like macro). E.g. #define A() replaces A() with nothing, but #define A () replaces A with ().