One drawback here. Imagine the following setup:

#include "colmap/util/logging.h"

#include <ExternalLibraryThatUsesGlogInHeader.h>

This will blow up when that external library uses glog's check macros in a way that our overrides don't support (e.g., CHECK(condition) << "message";.

This can also happen when colmap is installed as a library and other code uses glog. The v1 version of your PR added more code but does not have that problem?

As opposed to the previous PR, this one actually retains the syntax of glog by only overriding the internals. So CHECK(condition) << "message"; remains valid and any library using it in headers will simply throw an exception instead of aborting. If you think that this is confusing, we can:

1. Make this behavior optional with a CMake option, or
2. Name the macros differently to retain the behavior of glog's original checks

If option (2) is possible, then that sounds great to me and nobody sees unexpected behavior when using glog macros?

Done, PTAL.

Great, thanks!