cherry-pick from trunk: Remove one unnecesary call to Tcl_SetErrno() in DoReadChars().

1 files changed, 10 insertions, 8 deletions

diff --git a/generic/tclIO.c b/generic/tclIO.c
index 6ec93f2..92ad97e 100644
--- a/generic/tclIO.c
+++ b/generic/tclIO.c
@@ -6091,11 +6091,7 @@ DoReadChars(
 
 	    if (GotFlag(statePtr, CHANNEL_ENCODING_ERROR)
 		    && !GotFlag(statePtr, CHANNEL_STICKY_EOF)
-		    && !GotFlag(statePtr, CHANNEL_NONBLOCKING)) {
-		/* Channel is blocking.  Return an error so that callers
-		 * like [read] can return an error.
-		*/
-		Tcl_SetErrno(EILSEQ);
+		    && (!GotFlag(statePtr, CHANNEL_NONBLOCKING))) {
 		goto finish;
 	    }
 	}
@@ -6138,7 +6134,7 @@ finish:
     }
 
     /*
-     * Regenerate the top channel, in case it was changed due to
+     * Regenerate chanPtr in case it was changed due to
      * self-modifying reflected transforms.
      */
 
@@ -6160,8 +6156,14 @@ finish:
     assert(!(GotFlag(statePtr, CHANNEL_EOF|CHANNEL_BLOCKED)
             == (CHANNEL_EOF|CHANNEL_BLOCKED)));
     UpdateInterest(chanPtr);
+
+    /* This must comes after UpdateInterest(), which may set errno */
     if (GotFlag(statePtr, CHANNEL_ENCODING_ERROR)
 	    && (!copied || !GotFlag(statePtr, CHANNEL_NONBLOCKING))) {
+	/* Channel either is blocking or is nonblocking with no data
+	 * succesfully red before the error.  Return an error so that callers
+	 * like [read] can also return an error.
+	*/
 	Tcl_SetErrno(EILSEQ);
 	copied = -1;
     }
@@ -6200,7 +6202,7 @@ ReadBytes(
 				 * been allocated to hold data, not how many
 				 * bytes of data have been stored in the
 				 * object. */
-    int bytesToRead)		/* Maximum number of bytes to store, or < 0 to
+    int bytesToRead)		/* Maximum number of bytes to store, or -1 to
 				 * get all available bytes. Bytes are obtained
 				 * from the first buffer in the queue - even
 				 * if this number is larger than the number of
@@ -6597,7 +6599,7 @@ ReadChars(
 	     * precautions.
 	     */
 
-	    if (nextPtr->nextRemoved - srcLen < 0) {
+	    if (nextPtr->nextRemoved < srcLen) {
 		Tcl_Panic("Buffer Underflow, BUFFER_PADDING not enough");
 	    }