error when generating Vitis HLS in 2020.1: declaration of 'resize_accel' has a different language linkage

[jancumps]

I get errors when making the Vitis HLS project, with the 2020.1 toolchain:
https://github.com/Xilinx/PYNQ-HelloWorld/blob/master/boards/ip/hls/resize/Makefile

ERROR: [HLS 207-2542] declaration of 'resize_accel' has a different language linkage: xf_resize_accel.cpp:68:53

The function is declared as C in the cpp file:
extern "C" {
void resize_accel ...

When I try to declare it the same in xf_config_params.h, I get different issues:

INFO: [HLS 214-178] Inlining function 'xf::cv::Mat<9, 2160, 3840, 1>::read(int)' into 'void resizeNNBilinear<9, 2160, 3840, 1, 1080, 1920, 1, 2>(xf::cv::Mat<9, 2160, 3840, 1>&, xf::cv::Mat<9, 1080, 1920, 1>&)' (../vitis_lib/vision/L1/include\imgproc/xf_resize_nn_bilinear.hpp:277:0)
INFO: [HLS 214-178] Inlining function 'xf::cv::Mat<9, 1080, 1920, 1>::write(int, ap_uint<24>)' into 'void resizeNNBilinear<9, 2160, 3840, 1, 1080, 1920, 1, 2>(xf::cv::Mat<9, 2160, 3840, 1>&, xf::cv::Mat<9, 1080, 1920, 1>&)' (../vitis_lib/vision/L1/include\imgproc/xf_resize_nn_bilinear.hpp:277:0)
ERROR: [HLS 214-194] in function 'resize_accel': Undefined function xf::cv::_ssdm_op_alloc (../vitis_lib/vision/L1/include\common/xf_structs.hpp:527:9)
ERROR: [HLS 214-134] in function 'axis2xfMat(axis_t*, xf::cv::Mat<9, 2160, 3840, 1>&, int, int)': Pointer to pointer is not supported
ERROR: [HLS 214-134] in function 'void resizeNNBilinear<9, 2160, 3840, 1, 1080, 1920, 1, 2>(xf::cv::Mat<9, 2160, 3840, 1>&, xf::cv::Mat<9, 1080, 1920, 1>&)': Pointer to pointer is not supported
ERROR: [HLS 214-134] in function 'xfMat2axis(xf::cv::Mat<9, 1080, 1920, 1>&, axis_t*, int, int)': Pointer to pointer is not supported
ERROR: [HLS 214-135] Syn check fail!
Pre-synthesis failed.
    while executing
"source D:/users/jancu/git_pynq/PYNQ-HelloWorld/boards/ip/hls/resize/resize/solution1/csynth.tcl"
    invoked from within
"hls::main D:/users/jancu/git_pynq/PYNQ-HelloWorld/boards/ip/hls/resize/resize/solution1/csynth.tcl"
    ("uplevel" body line 1)
    invoked from within
"uplevel 1 hls::main {*}$args"
    (procedure "hls_proc" line 5)
    invoked from within
"hls_proc $argv"

I used this command to check out the GIT rep:
git clone --recursive https://github.com/Xilinx/PYNQ-HelloWorld.git

Then created the Vivado project using the resize.tcl script.
Then created the Vitis HCL project using the make script PYNQ-HelloWorld/blob/master/boards/ip/hls/resize/Makefile