From 2e3c6330c4079d113b4faeb0399aa8b19622710d Mon Sep 17 00:00:00 2001
From: David Woodhouse <dwmw2@infradead.org>
Date: Wed, 31 Mar 2021 14:35:33 +0100
Subject: [PATCH] Fix output redirection under Windows

If WriteConsoleW() fails, convert to the *console* code page and write to
stdout/stderr (as appropriate) with fwrite().

Mostly researched by bers in !177.

Fixes: #229

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
---
 main.c            | 31 +++++++++++++++++++++++++------
 www/changelog.xml |  1 +
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/main.c b/main.c
index c940a03f..ba5af16e 100644
--- a/main.c
+++ b/main.c
@@ -317,14 +317,33 @@ static int __attribute__ ((format(printf, 2, 0)))
 	HANDLE h = GetStdHandle(f == stdout ? STD_OUTPUT_HANDLE : STD_ERROR_HANDLE);
 	wchar_t wbuf[1024];
 	char buf[1024];
-	int chars, wchars;
+	int bytes, wchars;
 
-	buf[sizeof(buf) - 1] = 0;
-	chars = _vsnprintf(buf, sizeof(buf) - 1, fmt, args);
-	wchars = MultiByteToWideChar(CP_UTF8, 0, buf, -1, wbuf, sizeof(wbuf)/2);
-	WriteConsoleW(h, wbuf, wchars, NULL, NULL);
+	/* No need to NUL-terminate strings here */
+	bytes = _vsnprintf(buf, sizeof(buf), fmt, args);
+	if (bytes < 0)
+		return bytes;
+	if (bytes > sizeof(buf))
+		bytes = sizeof(buf);
 
-	return chars;
+	wchars = MultiByteToWideChar(CP_UTF8, 0, buf, bytes, wbuf, sizeof(wbuf)/2);
+	if (!wchars)
+		return -1;
+
+	/*
+	 * If writing to console fails, that's probably due to redirection.
+	 * Convert to console CP and write to the FH, following the example of
+	 * https://github.com/wine-mirror/wine/blob/e909986e6e/programs/whoami/main.c#L33-L49
+	 */
+	if (!WriteConsoleW(h, wbuf, wchars, NULL, NULL)) {
+		bytes = WideCharToMultiByte(GetConsoleOutputCP(), 0, wbuf, wchars,
+					    buf, sizeof(buf), NULL, NULL);
+		if (!bytes)
+			return -1;
+
+		return fwrite(buf, 1, bytes, f);
+	}
+	return bytes;
 }
 
 static int __attribute__ ((format(printf, 2, 3)))
diff --git a/www/changelog.xml b/www/changelog.xml
index 23085a53..3027ee71 100644
--- a/www/changelog.xml
+++ b/www/changelog.xml
@@ -36,6 +36,7 @@
        <li>Add support for PPP-based protocols, currently over TLS only (<a href="https://gitlab.com/openconnect/openconnect/-/merge_requests/165">!165</a>).</li>
        <li>Add support for two PPP-based protocols, F5 with <tt>--protocol=f5</tt> and Fortinet with <tt>--protocol=fortinet</tt> (<a href="https://gitlab.com/openconnect/openconnect/-/merge_requests/169">!169</a>).</li>
        <li>Add support for <a href="https://www.wintun.net/">Wintun</a> Layer 3 TUN driver under Windows.</li>
+       <li>Fix output redirection under Windows (<a href="https://gitlab.com/openconnect/openconnect/-/issues/229">#229</a>)</li>
      </ul><br/>
   </li>
   <li><b><a href="ftp://ftp.infradead.org/pub/openconnect/openconnect-8.10.tar.gz">OpenConnect v8.10</a></b>
-- 
2.50.1