From daa816fc2e7c6cbb669ba030d45dd979ef37f7c2 Mon Sep 17 00:00:00 2001
From: Karen Arutyunov <karen@codesynthesis.com>
Date: Sat, 15 Dec 2018 17:19:47 +0300
Subject: Fix line counting in cc::lexer

---
 build2/depdb.cxx | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

(limited to 'build2/depdb.cxx')

diff --git a/build2/depdb.cxx b/build2/depdb.cxx
index f89daba..c963387 100644
--- a/build2/depdb.cxx
+++ b/build2/depdb.cxx
@@ -117,7 +117,9 @@ namespace build2
     if (trunc)
       fdtruncate (fd.get (), pos_);
 
-    // Note: seek is required to switch from reading to writing.
+    // Note: the file descriptor position can be beyond the pos_ value due to
+    // the ifdstream buffering. That's why we need to seek to switch from
+    // reading to writing.
     //
     fdseek (fd.get (), pos_, fdseek_mode::set);
 
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