include missing on Ubuntu 20.04

[joga111]

When building on Ubuntu 20.04 I got a broken build:

g++ -DHAVE_CONFIG_H -I. -I../../src -I../common    -O2 -Wall -Wno-unknown-pragmas   -MT CupsPrintEnvironment.o -MD -MP -MF .deps/CupsPrintEnvironment.Tpo -c -o CupsPrintEnvironment.o `test -f '../common/CupsPrintEnvironment.cpp' || echo './'`../common/CupsPrintEnvironment.cpp
../common/CupsPrintEnvironment.cpp: In member function ‘virtual void DymoPrinterDriver::CCupsPrintEnvironmentForLM::ReadData(DymoPrinterDriver::buffer_t&)’:
../common/CupsPrintEnvironment.cpp:139:23: error: ‘cupsBackChannelRead’ was not declared in this scope
  139 |   ssize_t bytesRead = cupsBackChannelRead((char*)buf, sizeof(buf), 2.5);
      |                       ^~~~~~~~~~~~~~~~~~~

An additional include

#include <cups/sidechannel.h>

Seems to fix it.
Thank you for providing this updated dymo sdk!

[JJTechman68]

Where do I add the missing include?

[joga111]

In src/common/CupsPrintEnvironment.cpp, I should have added the diff:

diff --git a/src/common/CupsPrintEnvironment.cpp b/src/common/CupsPrintEnvironment.cpp
index 1bee24d..e9034a5 100644
--- a/src/common/CupsPrintEnvironment.cpp
+++ b/src/common/CupsPrintEnvironment.cpp
@@ -23,6 +23,7 @@
 #include "CupsPrintEnvironment.h"
 #include <errno.h>
 #include <cups/cups.h>
+#include <cups/sidechannel.h>
 #include <cassert>
 
 namespace DymoPrinterDriver