fmt: Scanf / Sscanf does not properly treat carriage return symbol, behaves different with C function

[RodionGork]

Go version

go1.23

Output of go env in your module/workspace:

GO...=n/a

What did you do?

Here is an example in playground https://go.dev/play/p/z7Rd0o0PiJH

We simply try reading with fmt.Sscanf (from the prepared string, but it is the same with fmt.Scanf reading from stdin - just more difficult to demonstrate) - there are two integer values, separated with windows-style newline (\r\n).

	var x, y int
	input := "5\r\n8\r\n"
	fmt.Sscanf(input, "%d %d", &x, &y)
	fmt.Println(x, y)

What did you see happen?

It prints 5 0

What did you expect to see?

It should print 5 8

C code for comparing behavior:

#include <stdio.h>

int main() {
  char s[] = "5\r\n8\r\n";
  int x, y;
  sscanf(s, "%d %d", &x, &y);
  printf("%d %d\n", x, y);
  return 0;
}

Also this is not in concordance with package description here https://pkg.go.dev/fmt

In all the scanning functions, a carriage return followed immediately by a newline
is treated as a plain newline (\r\n means the same as \n).

[seankhliao]

A newline is not a space, even without \r your line won't match.

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