Can't build on Ubuntu 20.04 with latest libplacebo

[lcksk]

The default GCC compiler version 9.4.0 in Ubuntu 20.04 does not support C++20 features perfectly, the latest version of libplacebo on Ubuntu 20.04 encounters the following errors during compilation:

FAILED: src/libplacebo.a.p/convert.cc.o 
ccache c++ -Isrc/libplacebo.a.p -Isrc -I../src -Isrc/include -I../src/include -I../3rdparty/Vulkan-Headers/include -I../3rdparty/fast_float/include -Isrc/opengl/include -I../src/opengl/include -Isrc/shaders -Isrc/vulkan -Isrc/opengl/include/glad -I/usr/include/x86_64-linux-gnu -fvisibility=hidden -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=c++2a -O2 -g -Wundef -Wshadow -Wparentheses -Wpointer-arith -fPIC -pthread -DPL_HAVE_PTHREAD -DPTHREAD_HAS_SETCLOCK -MD -MQ src/libplacebo.a.p/convert.cc.o -MF src/libplacebo.a.p/convert.cc.o.d -o src/libplacebo.a.p/convert.cc.o -c ../src/convert.cc
../src/convert.cc:34:1: error: 'concept' does not name a type
   34 | concept has_std_to_chars = requires(char *begin, char *end, T &n)
      | ^~~~~~~
../src/convert.cc:34:1: note: 'concept' only available with '-fconcepts'
../src/convert.cc: In function 'int {anonymous}::to_chars(char*, size_t, T, Args ...)':
../src/convert.cc:42:19: error: 'has_std_to_chars' was not declared in this scope
   42 |     if constexpr (has_std_to_chars<T>) {
      |                   ^~~~~~~~~~~~~~~~
../src/convert.cc:42:37: error: expected primary-expression before '>' token
   42 |     if constexpr (has_std_to_chars<T>) {
      |                                     ^
../src/convert.cc:42:38: error: expected primary-expression before ')' token
   42 |     if constexpr (has_std_to_chars<T>) {
      |                                      ^
../src/convert.cc: At global scope:
../src/convert.cc:56:1: error: 'concept' does not name a type
   56 | concept has_std_from_chars = requires(const char *begin, const char *end, T &n)
      | ^~~~~~~
../src/convert.cc:56:1: note: 'concept' only available with '-fconcepts'
../src/convert.cc: In function 'bool {anonymous}::from_chars(pl_str, T&, Args ...)':
../src/convert.cc:64:19: error: 'has_std_from_chars' was not declared in this scope
   64 |     if constexpr (has_std_from_chars<T>) {
      |                   ^~~~~~~~~~~~~~~~~~
../src/convert.cc:64:39: error: expected primary-expression before '>' token
   64 |     if constexpr (has_std_from_chars<T>) {
      |                                       ^
../src/convert.cc:64:40: error: expected primary-expression before ')' token
   64 |     if constexpr (has_std_from_chars<T>) {
      |                                        ^
../src/convert.cc: In instantiation of 'int {anonymous}::to_chars(char*, size_t, T, Args ...) [with T = short unsigned int; Args = {int}; size_t = long unsigned int]':
../src/convert.cc:99:1:   required from here
../src/convert.cc:46:48: error: static assertion failed: Not implemented!
   46 |         static_assert(std::is_same_v<float, T> || std::is_same_v<double, T>,
      |                       ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
../src/convert.cc: In instantiation of 'bool {anonymous}::from_chars(pl_str, T&, Args ...) [with T = short unsigned int; Args = {int}; pl_str = pl_str]':
../src/convert.cc:99:1:   required from here
../src/convert.cc:71:23: error: static assertion failed: Not implemented!
   71 |         static_assert(is_fp, "Not implemented!");
      |                       ^~~~~
../src/convert.cc:79:48: error: no matching function for call to 'from_chars(const char*, const char*, short unsigned int&, int&)'
   79 |         auto [ptr, ec] = fast_float::from_chars((const char *) str.buf,
      |                          ~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
   80 |                                                 (const char *) str.buf + str.len,
      |                                                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   81 |                                                 n, args...);
      |                                                 ~~~~~~~~~~~
In file included from ../3rdparty/fast_float/include/fast_float/fast_float.h:41,

build.log

[kasper93]

Duplicate of haasn/libplacebo#199