/dev/clipboard sometimes fails to set CF_UNICODETEXT data.

Takashi Yano takashi.yano@nifty.ne.jp
Sat Jul 2 03:20:56 GMT 2022


In one of my PCs,
dd if=/dev/urandom count=10 | xxd > /dev/clipboard
sometimes fails to set CF_UNICODETEXT data.
As a result, pasting clipboard to notepad does not work.

Even in the case, cygnativeformat data is set correctly.
So, "cat /dev/clipboard" works.

This problem depends on machine very much.

My one PC with Xeon E3-1281 v3 CPU has a high probability of failure,
however, another machine with Core i7-6700K CPU does not.

I looked into this problem, and found OpenClipboard() for
CF_UNICODETEXT fails. It seems that OpenClipboard() just
after CloseClipboard() has high probability of failure.

You can see the following test case immediately stops with error.
Even with Core i7-6700K CPU machine above, the test case fails.

#include <windows.h>
#include <stdio.h>

int main()
	for (;;) {
		if (!OpenClipboard(0)) {
			printf("Open error.\n");
		if (!EmptyClipboard()) {
			printf("Empty error.\n");
		if (!CloseClipboard()) {
			printf("Cloes error.\n");
	return 0;

I also found the patch attached solves the issue.

I would appreciate any suggestion.

Takashi Yano <takashi.yano@nifty.ne.jp>
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