Merge pull request #8517 from vali0901/issue_13893

Fix Issue 13893 - rawRead must take a non-empty buffer

std/stdio.d

@@ -1132,10 +1132,9 @@ each item is inferred from the size and type of the input array, respectively.
 
 Returns: The slice of `buffer` containing the data that was actually read.
 This will be shorter than `buffer` if EOF was reached before the buffer
-could be filled.
+could be filled. If the buffer is empty, it will be returned.
 
-Throws: `Exception` if `buffer` is empty.
-        `ErrnoException` if the file is not opened or the call to `fread` fails.
+Throws: `ErrnoException` if the file is not opened or the call to `fread` fails.
 
 `rawRead` always reads in binary mode on Windows.
  */
@@ -1144,7 +1143,7 @@ Throws: `Exception` if `buffer` is empty.
         import std.exception : enforce, errnoEnforce;
 
         if (!buffer.length)
-            throw new Exception("rawRead must take a non-empty buffer");
+            return buffer;
         enforce(isOpen, "Attempting to read from an unopened file");
         version (Windows)
         {
@@ -1211,6 +1210,16 @@ Throws: `Exception` if `buffer` is empty.
         }
     }
 
+    // https://issues.dlang.org/show_bug.cgi?id=13893
+    @system unittest
+    {
+        import std.exception : assertNotThrown;
+
+        File f;
+        ubyte[0] u;
+        assertNotThrown(f.rawRead(u));
+    }
+
 /**
 Calls $(HTTP cplusplus.com/reference/clibrary/cstdio/fwrite.html, fwrite) for the file
 handle. The number of items to write and the size of each