#6 configure: error: your version of g++ seems to be too old.

[Chuck Coleman]

This probably has to do with using a Mac. I had to use homebrew to install the latest versions of gcc, etc., then use aliases to point to them: Here's the transcript:

Coleman-iMac:pstoedit-3.75 Common$ ./configure
checking for a BSD-compatible install... /usr/bin/install -c
checking whether build environment is sane... yes
checking for a thread-safe mkdir -p... ./install-sh -c -d
checking for gawk... gawk
checking whether make sets $(MAKE)... yes
checking whether make supports nested variables... yes
checking for gcc... gcc
checking whether the C compiler works... yes
checking for C compiler default output file name... a.out
checking for suffix of executables...
checking whether we are cross compiling... no
checking for suffix of object files... o
checking whether we are using the GNU C compiler... yes
checking whether gcc accepts -g... yes
checking for gcc option to accept ISO C89... none needed
checking whether gcc understands -c and -o together... yes
checking for style of include used by make... GNU
checking dependency style of gcc... gcc3
checking for g++... g++
checking whether we are using the GNU C++ compiler... yes
checking whether g++ accepts -g... yes
checking dependency style of g++... gcc3
checking for g++ std... configure: error: your version of g++ seems to be too old.
Coleman-iMac:pstoedit-3.75 Common$ gcc --version
gcc-9 (Homebrew GCC 9.3.0_1) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Coleman-iMac:pstoedit-3.75 Common$ g++ --version
g++-9 (Homebrew GCC 9.3.0_1) 9.3.0
Copyright (C) 2019 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[Wolfgang Glunz]

Hi Chuck,

could you please do a small test.
Put this line into a new file, e.g. test.cpp

constexpr int ce = 10; int * p = nullptr;

And then run
g++ -c test.cpp

What is the output ?

Thanks
Wolfgang

[Chuck Coleman]

test.cpp:1:1: error: unknown type name 'constexpr'
constexpr int ce = 10; int * p = nullptr;
^
test.cpp:1:11: error: expected unqualified-id
constexpr int ce = 10; int * p = nullptr;
^
test.cpp:1:34: error: use of undeclared identifier 'nullptr'
constexpr int ce = 10; int * p = nullptr;
^
3 errors generated.

[Wolfgang Glunz]

But that confirms that your compiler version is too old.
But g++ 9 accepts this file. So you seem to call still the older version somehow.