# HG changeset patch
# User Martin von Zweigbergk <martinvonz@google.com>
# Date 2015-03-12 16:06:45
# Node ID 40528ad1b1e8a00f1a952ba8d26a44bcba7a5ec1
# Parent  8e13cc0825f17a8e7def3a378ebed036f36e738f

lazymanifest: don't depend on printf's 'hh' format to work

Where we convert a 20-byte binary to a 40-byte hex string in
lazymanifest_setitem(), we use sprintf("%02hhx", hash[i]). As Matt
Harbison found out, 'hh' seems to be ignored on some platforms (Visual
Studio?). If char is signed on such platforms, the value gets
sign-extended as it gets promoted into an int when passed into the
variadic sprintf(). The resulting integer value will then be printed
with leading f's (14 of them on 64-bit systems), since the '2' in the
format string indicates only minimum number of characters. This is
both incorrect and runs the risk of writing outside of allocated
memory (as Matt reported).

To fix, let's cast the value to unsigned char before passing it to
sprintf(). Also drop the poorly supported 'hh' formatting that now
becomes unnecessary.

diff --git a/mercurial/manifest.c b/mercurial/manifest.c
--- a/mercurial/manifest.c
+++ b/mercurial/manifest.c
@@ -466,7 +466,10 @@ static int lazymanifest_setitem(
 	}
 	memcpy(dest, path, plen + 1);
 	for (i = 0; i < 20; i++) {
-		sprintf(dest + plen + 1 + (i * 2), "%02hhx", hash[i]);
+		/* Cast to unsigned, so it will not get sign-extended when promoted
+		 * to int (as is done when passing to a variadic function)
+		 */
+		sprintf(dest + plen + 1 + (i * 2), "%02x", (unsigned char)hash[i]);
 	}
 	memcpy(dest + plen + 41, flags, flen);
 	dest[plen + 41 + flen] = '\n';