This is an occasional re-reminder that anything in the C standard library that is locale-sensitive is fundamentally broken and should not be used.
Today's example is strerr(), which returns a string that is meant to be rendered to the user, but the string isn't guaranteed to be UTF-8. On Mon, Aug 27, 2018 at 3:04 PM Henri Sivonen <hsivo...@mozilla.com> wrote: > > Please don't use the functions from ctype.h and strings.h. > > See: > https://daniel.haxx.se/blog/2018/01/30/isalnum-is-not-my-friend/ > https://daniel.haxx.se/blog/2008/10/15/strcasecmp-in-turkish/ > https://stackoverflow.com/questions/2898228/can-isdigit-legitimately-be-locale-dependent-in-c > > In addition to these being locale-sensitive, the functions from > ctype.h are defined to take (signed) int with the value space of > *unsigned* char or EOF and other argument values are Undefined > Behavior. Therefore, on platforms where char is signed, passing a char > sign-extends to int and invokes UB if the most-significant bit of the > char was set! Bug filed 15 years ago! > https://bugzilla.mozilla.org/show_bug.cgi?id=216952 (I'm not aware of > implementations doing anything surprising with this UB but there > exists precedent for *compiler* writers looking at the standard > *library* UB language and taking calls into standard library functions > as optimization-guiding assertions about the values of their > arguments, so better not risk it.) > > For isfoo(), please use mozilla::IsAsciiFoo() from mozilla/TextUtils.h. > > For tolower() and toupper(), please use ToLowerCaseASCII() and > ToUpperCaseASCII() from nsUnicharUtils.h > > For strcasecmp() and strncasecmp(), please use their nsCRT::-prefixed > versions from nsCRT.h. > > (Ideally, we should scrub these from vendored C code, too, since being > in third-party code doesn't really make the above problems go away.) > > -- > Henri Sivonen > hsivo...@mozilla.com -- Henri Sivonen hsivo...@mozilla.com _______________________________________________ dev-platform mailing list dev-platform@lists.mozilla.org https://lists.mozilla.org/listinfo/dev-platform
