OpenCL runtime error -42 (CL_INVALID_BINARY) trying to instantiate cl::Program object.

I created a simple OpenCL application with a trivial FPGA kernel to verify the build/run process, but am getting a -42 error code returned from the cl::Program constructor. Here's a snippet of the host:

// Read kernel binary (compiled with "aoc -v -board=a10gx_hostpipe pipes.cl"):
   std::ifstream aocx_stream("pipes.aocx", std::ios::in|std::ios::binary);
   checkErr(aocx_stream.is_open() ? CL_SUCCESS:-1, "Opening pipes.aocx");
   std::string progBuf(std::istreambuf_iterator<char>(aocx_stream),
                       (std::istreambuf_iterator<char>()));
   cl::Program::Binaries binaries;
   binaries.push_back(std::make_pair((const void*)progBuf.c_str(), progBuf.length()));
 
   // Create the Program from the AOCX binary:
   cl::Program program(context, DeviceList, binaries, NULL, &err); // RETURNS err=-42
   checkErr(err, "Program Constructor"); // THROWS EXCEPTION
 

When I use the emulation platform/device with the aocx binary compiled for that target, the code above works. But when I try it using the h/w platform/device, it fails with -42. I compiled pipes.cl with the command:

aoc -v -board=a10gx_hostpipe pipes.cl

I was successful programming the device from the command line with

$ aocl program acl0 ./pipes.aocx
aocl program: Running program from /home/okramer/intelFPGA_pro/19.3/hld/board/a10_ref/linux64/libexec
Programming device: a10gx : Arria 10 Reference Platform (acla10_ref0)
MMD INFO : [acla10_ref0] Quartus versions for base and import compile do not match
MMD INFO : [acla10_ref0] Board is currently programmed with sof from Quartus 19.3.0 171
MMD INFO : [acla10_ref0] PR import was compiled with Quartus 19.3.0 222
MMD INFO : [acla10_ref0] Reprogram the device with data saving and restoring
MMD INFO : [acla10_ref0] Trying Partial Reconfiguration
MMD INFO : [acla10_ref0] Quartus versions for base and import compile do not match
MMD INFO : [acla10_ref0] Board is currently programmed with sof from Quartus 19.3.0 171
MMD INFO : [acla10_ref0] PR import was compiled with Quartus 19.3.0 222
MMD INFO : [acla10_ref0] Trying Full-Chip Reconfiguration (JTAG)
MMD INFO : JTAG Autodetect device found Cable:1 , Device Index:1
MMD INFO : setting Cable to autodetect value 1 
MMD INFO : setting Device Index to autodetect value 1
MMD INFO : executing "quartus_pgm -c 1  -m jtag -o "P;reprogram_temp.sof@1""
Info: *******************************************************************
Info: Running Quartus Prime Programmer
    Info: Version 19.3.0 Build 222 09/23/2019 SC Pro Edition
    Info: Copyright (C) 2019  Intel Corporation. All rights reserved.
    Info: Your use of Intel Corporation's design tools, logic functions 
    Info: and other software and tools, and any partner logic 
    Info: functions, and any output files from any of the foregoing 
    Info: (including device programming or simulation files), and any 
    Info: associated documentation or information are expressly subject 
    Info: to the terms and conditions of the Intel Program License 
    Info: Subscription Agreement, the Intel Quartus Prime License Agreement,
    Info: the Intel FPGA IP License Agreement, or other applicable license
    Info: agreement, including, without limitation, that your use is for
    Info: the sole purpose of programming logic devices manufactured by
    Info: Intel and sold by Intel or its authorized distributors.  Please
    Info: refer to the applicable agreement for further details, at
    Info: https://fpgasoftware.intel.com/eula.
    Info: Processing started: Thu Jan  9 17:22:26 2020
    Info: System process ID: 15973
Info: Command: quartus_pgm -c 1 -m jtag -o P;reprogram_temp.sof@1
Info (213045): Using programming cable "USB-BlasterII [1-5]"
Info (213011): Using programming file reprogram_temp.sof with checksum 0x30EEE395 for device 10AX115S2F45@1
Info (209060): Started Programmer operation at Thu Jan  9 17:22:31 2020
Info (209016): Configuring device index 1
Info (209017): Device 1 contains JTAG ID code 0x02E660DD
Info (209007): Configuration succeeded -- 1 device(s) configured
Info (209011): Successfully performed operation(s)
Info (209061): Ended Programmer operation at Thu Jan  9 17:22:46 2020
Info: Quartus Prime Programmer was successful. 0 errors, 0 warnings
    Info: Peak virtual memory: 2527 megabytes
    Info: Processing ended: Thu Jan  9 17:22:46 2020
    Info: Elapsed time: 00:00:20
    Info: System process ID: 15973
Program succeed.

I asked a related question as a follow-up to previous posting here: https://forums.intel.com/s/question/0D70P000006e8m7SAA. I'm not sure it's relevant.