Conditionally-off blocks of code under #ifdefs are challenging for it, yes - it runs a proper C++ compiler on your code and won't get to see code in those block

Conditionally-off blocks of code under #ifdefs are challenging for it, yes - it runs a proper C++ compiler on your code and won't get to see code in those blocks without the right defines. Don't blindly apply its suggestions - test them, skim to see what it got wrong, sprinkle some "// IWYU pragma: keep" to help it out in corner cases. The tool is more like a linter, you don't follow everything that your linter tells you to, no?