From 29c9bdcc141afb14fc9e1213f49de4fcded6ce0c Mon Sep 17 00:00:00 2001
From: practicalswift <practicalswift@users.noreply.github.com>
Date: Wed, 2 May 2018 12:12:55 +0200
Subject: [PATCH] Handle unsuccessful fseek(...):s

---
 src/index/txindex.cpp | 4 +++-
 src/logging.cpp       | 5 ++++-
 src/util.cpp          | 4 +++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/src/index/txindex.cpp b/src/index/txindex.cpp
index 2a661f033..ad1682c9c 100644
--- a/src/index/txindex.cpp
+++ b/src/index/txindex.cpp
@@ -268,7 +268,9 @@ bool TxIndex::FindTx(const uint256& tx_hash, uint256& block_hash, CTransactionRe
     CBlockHeader header;
     try {
         file >> header;
-        fseek(file.Get(), postx.nTxOffset, SEEK_CUR);
+        if (fseek(file.Get(), postx.nTxOffset, SEEK_CUR)) {
+            return error("%s: fseek(...) failed", __func__);
+        }
         file >> tx;
     } catch (const std::exception& e) {
         return error("%s: Deserialize or I/O error - %s", __func__, e.what());
diff --git a/src/logging.cpp b/src/logging.cpp
index 10a3b1895..2a55d3665 100644
--- a/src/logging.cpp
+++ b/src/logging.cpp
@@ -254,7 +254,10 @@ void BCLog::Logger::ShrinkDebugFile()
     {
         // Restart the file with some of the end
         std::vector<char> vch(RECENT_DEBUG_HISTORY_SIZE, 0);
-        fseek(file, -((long)vch.size()), SEEK_END);
+        if (fseek(file, -((long)vch.size()), SEEK_END)) {
+            fclose(file);
+            return;
+        }
         int nBytes = fread(vch.data(), 1, vch.size(), file);
         fclose(file);
 
diff --git a/src/util.cpp b/src/util.cpp
index 9a3067259..b4d0a61ab 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -887,7 +887,9 @@ void AllocateFileRange(FILE *file, unsigned int offset, unsigned int length) {
     // Fallback version
     // TODO: just write one byte per block
     static const char buf[65536] = {};
-    fseek(file, offset, SEEK_SET);
+    if (fseek(file, offset, SEEK_SET)) {
+        return;
+    }
     while (length > 0) {
         unsigned int now = 65536;
         if (length < now)