I think that found an error in the stdio module.
When reading the file consisting of entries in the coding UTF-8, type:

.......
16235;Иванов;Петр;Петрович;17.09.1961
8765;Петров;Иван;Васильевич;25.12.1978
.......

total quantity of records about 30000

there are errors: invalid secuence Utf-8

Research of a problem showed that results failure from reading from the buffer of the next character the FGETC function (cast(_iobuf*)_f. _ p.handle) in the takeFront procedure. And, over time failure happens only provided that characters return to the (cast(_iobuf*)_f. _ p.handle) the ungetc() function. If it is simple to realize reading characters, without returning them the ungetc function(), this error isn't shown. For example it was absent in the dmd 2.066 version where in stdio.d the ungetc function wasn't used().

Error in std.stdio.d
This example doesn't work!

// dmd 2.067.1 Win 32
import std.stdio;

void main(string[] args) {
	File fw = File("panic.csv", "w");
	for(int i; i != 5000; i++) {
		fw.writeln(i, ";", "Иванов;Пётр;Иванович");
	}
	fw.close();
	// Test read
	File fr = File("panic.csv", "r");
	int nom; string fam, nam, ot;
	// Error format read
	while(!fr.eof) fr.readf("%s;%s;%s;%s\n", &nom, &fam, &nam, &ot);
}

This mistake, is result of wrong algorithm with reading from the ring buffer of the file and return of the read symbols there in stdio function ungetc().

On Sunday, 2 August 2015 at 06:01:01 UTC, MGW wrote:
> Error in std.stdio.d
> This example doesn't work!
>
> // dmd 2.067.1 Win 32
> import std.stdio;
>
> void main(string[] args) {
> 	File fw = File("panic.csv", "w");
> 	for(int i; i != 5000; i++) {
> 		fw.writeln(i, ";", "Иванов;Пётр;Иванович");
> 	}
> 	fw.close();
> 	// Test read
> 	File fr = File("panic.csv", "r");
> 	int nom; string fam, nam, ot;
> 	// Error format read
> 	while(!fr.eof) fr.readf("%s;%s;%s;%s\n", &nom, &fam, &nam, &ot);
> }
>
> This mistake, is result of wrong algorithm with reading from the ring buffer of the file and return of the read symbols there in stdio function ungetc().

Please report the issue at https://issues.dlang.org if you have not already.

- Jonathan M Davis