- Prefer cstddef over cstdlib for size_t definition - fewer overall definitions
- Include cstdlib where used, and note which definitions are used
I used iwyu and the following regex to check for usage:
stdlib\.h|\bEXIT_SUCCESS\b|\bEXIT_FAILURE\b|\bMB_CUR_MAX\b|\bRAND_MAX\b|\bdiv_t\b|\bldiv_t\b|\blldiv_t\b|\babort\(|[^.]exit\(|\bquick_exit\(|\b_Exit\(|\batexit\(|\bat_quick_exit\(|\bsystem\(|[^.]getenv\(|\bmalloc\(|\bcalloc\(|\brealloc\(|[^.]free\(|\batof\(|\batoi\(|\batol\(|\batoll\(|\bstrtol\(|\bstrtoll\(|\bstrtoul\(|\bstrtoull\(|\bstrtof\(|\bstrtod\(|\bstrtold\(|\bmblen\(|\bmbtowc\(|\bwctomb\(|\bmbstowcs\(|\bwcstombs\(|\brand\(|\bsrand\(|\bqsort\(|\bbsearch\(|\babs\(|\blabs\(|\bllabs\(|\bdiv\(|\bldiv\(|\blldiv\(
Prompted by initial look at include-what-you-use tool.