two strings separated by blank being concatenated automatically

Question

I just found something very interesting which was introduced by my typo. Here's a sample of very easy code script:

printf("A" "B");

The result would be

$> AB

Can someone explain how this happens?

Answer 1

As a part of the C standard, string literals that are next to one another are concatenated:

For C (quoting C99, but C11 has something similar in 6.4.5p5):

(C99, 6.4.5p5) "In translation phase 6, the multibyte character sequences specified by any sequence of adjacent character and identically-prefixed string literal tokens are concatenated into a single multibyte character sequence."

C++ has a similar standard.

Answer 2

这是标准行为，在将非常长的字符串常量分割为多行时非常有用。

Answer 3

This is string concatenation, part of C standard. Any two or more consecutive string literals are combined into one.