compile error: use of overloaded operator '<<' is ambiguous

[xingx1]

I'm using Ubuntu 18.04.4 LTS (Bionic Beaver), clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final), cmake version 3.10.2.
I cloned, compiled, installed the project, and trying to use it in my own project.
But once I included the header "glog/logging.h", I got an compile error like:

_/usr/local/include/glog/logging.h:649:9: error: use of overloaded operator '<<' is ambiguous 
(with operand types 'std::ostream' (aka 'basic_ostream<char>') and 'const nullptr_t')
  (*os) << v;_

Did this because the use of the operator is really ambiguous or there's implicit incompatible with some cmake settings I made?

---

I found it is because that CHECK_NE() is not suitable to estimate a pointer to nullptr.
Try following code:

#include "glog/logging.h"
#include <iostream>

int main() {
    int i = 0;
    CHECK_NE(&i, nullptr);
    return 0;
}

[Mizux]

Got this bug on Google OR-Tools too. It may come from the version of the gcc compiler

Result I got:

• alpine, archlinux, fedora OK (gcc 10.2)
• ubuntu OK (gcc 9.3)
• centos FAIL (gcc 8.3.1)
• debian FAIL (gcc 8.3.0)

ref: https://github.com/google/or-tools/actions/runs/315808746

• runner ubuntu github FAIL (gcc 7.5.0)

ref: https://github.com/google/or-tools/runs/1276111332?check_suite_focus=true

[Mizux]

FYI, a simple workaround, is to replace:

• CHECK_NE(..., nullptr) by CHECK(... != nullptr) and
• CHECK_EQ(..., nullptr) by CHECK(... == nullptr)

Otherwise you may also cherry pick the PR #342