Improving reliability and information from the large file test

Saw a couple of sporadic failures on Windows platforms. Debug output
should help find what's happening.

Once the fillFileSparsely test fails, there's no point in trying to read
what we failed to write so maximum tested size is reset on a failed
write.

Reviewed-by: Markus Goetz

1 files changed, 35 insertions, 0 deletions

diff --git a/tests/auto/qfile/largefile/tst_largefile.cpp b/tests/auto/qfile/largefile/tst_largefile.cpp
index 8ab3275c0c..9105063e73 100644
--- a/tests/auto/qfile/largefile/tst_largefile.cpp
+++ b/tests/auto/qfile/largefile/tst_largefile.cpp
@@ -339,12 +339,47 @@ void tst_LargeFile::fillFileSparsely()
     QFETCH( QByteArray, block );
     QCOMPARE( block.size(), blockSize );
 
+    static int lastKnownGoodIndex = 0;
+    struct ScopeGuard {
+        ScopeGuard(tst_LargeFile* test)
+            : this_(test)
+            , failed(true)
+        {
+            QFETCH( int, index );
+            index_ = index;
+        }
+
+        ~ScopeGuard()
+        {
+            if (failed) {
+                this_->maxSizeBits = lastKnownGoodIndex;
+                QWARN( qPrintable(
+                    QString("QFile::error %1: '%2'. Maximum size bits reset to %3.")
+                        .arg(this_->largeFile.error())
+                        .arg(this_->largeFile.errorString())
+                        .arg(this_->maxSizeBits)) );
+            } else
+                lastKnownGoodIndex = qMax<int>(index_, lastKnownGoodIndex);
+        }
+
+    private:
+        tst_LargeFile * const this_;
+        int index_;
+
+    public:
+        bool failed;
+    };
+
+    ScopeGuard resetMaxSizeBitsOnFailure(this);
+
     QVERIFY( largeFile.seek(position) );
     QCOMPARE( largeFile.pos(), position );
 
     QCOMPARE( largeFile.write(block), (qint64)blockSize );
     QCOMPARE( largeFile.pos(), position + blockSize );
     QVERIFY( largeFile.flush() );
+
+    resetMaxSizeBitsOnFailure.failed = false;
 }
 
 void tst_LargeFile::fileCreated()