Hi,

I am on ubuntu 20.04, I have GCC9.4 and 10.3 and 11.1 installed.

I found that when set "-std=c++20", with gcc11, boost.gil will failed to build.

Here is the simple test cpp to reproduce the issue:

#include <sstream>

#include <boost/gil.hpp>

#include <boost/gil/extension/io/png.hpp>

namespace gil = boost::gil;

int main()

{

  gil::rgb8_image_t img;

  std::stringstream buf(std::ios::in | std::ios::out | std::ios::binary);

  gil::read_and_convert_image(buf, img, gil::png_tag{});

 

  return 0;

}

the build command is:

g++ -o test test_gcc11_gil.cc -std=c++20 -I${THIRD_PARTY}/boost/boost_1_78_0 -L${THIRD_PARTY}/libpng/1.6.37/lib/ -lpng

If replaced '-std=c++20' with '-std=c++17', the build would be OK,  but with 'c++20', gcc 11 failed with the following errors:

In file included from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/read.hpp:13,

from /data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png.hpp:11,

from test_gcc11_gil.cc:3:

/data/lin/ThirdParty/boost/boost_1_78_0/boost/gil/extension/io/png/tags.hpp:576:32: error: expected unqualified-id before ‘)’ token

576 |     image_read_info< png_tag >()

|                                ^