Fix QSslSocket::constructing autotest failure

The optimizations in d0645d1792e1cbdf417a923ea071975e4390fccd did not
take into account 0-length reads, used in network programming to check
connected state.

By not returning early in the case where lastReadChunkSize == maxSize
and maxSize == 0, we allow the underlying device to report error
conditions on 0-length reads.

This reverts commit aea71e2e02fa966842b094244bc3f5fc88f50f41, while
still ensuring that QIODevice::read() returns -1 on a closed device.

Reviewed-by: mread
Reviewed-by: Thiago Macieira

1 files changed, 6 insertions, 7 deletions

diff --git a/src/corelib/io/qiodevice.cpp b/src/corelib/io/qiodevice.cpp
index f2cef4e1..bb11d6b 100644
--- a/src/corelib/io/qiodevice.cpp
+++ b/src/corelib/io/qiodevice.cpp
@@ -755,7 +755,6 @@ qint64 QIODevice::bytesToWrite() const
 qint64 QIODevice::read(char *data, qint64 maxSize)
 {
     Q_D(QIODevice);
-    CHECK_READABLE(read, qint64(-1));
 
 #if defined QIODEVICE_DEBUG
     printf("%p QIODevice::read(%p, %d), d->pos = %d, d->buffer.size() = %d\n",
@@ -786,13 +785,13 @@ qint64 QIODevice::read(char *data, qint64 maxSize)
     do {
         // Try reading from the buffer.
         int lastReadChunkSize = d->buffer.read(data, maxSize);
-        *d->pPos += lastReadChunkSize;
-        readSoFar += lastReadChunkSize;
-        // fast exit when satisfied by buffer
-        if (lastReadChunkSize == maxSize && !(d->openMode & Text))
-            return readSoFar;
-
         if (lastReadChunkSize > 0) {
+            *d->pPos += lastReadChunkSize;
+            readSoFar += lastReadChunkSize;
+            // fast exit when satisfied by buffer
+            if (lastReadChunkSize == maxSize && !(d->openMode & Text))
+                return readSoFar;
+
             data += lastReadChunkSize;
             maxSize -= lastReadChunkSize;
 #if defined QIODEVICE_DEBUG