[libc] build libc++

[michaelrj-google]

This is the overall tracking bug for building libc++ against LLVM-libc.

[llvmbot]

@llvm/issue-subscribers-libc

Author: Michael Jones (michaelrj-google)

Details

This is the overall tracking bug for building libc++ against LLVM-libc.

[michaelrj-google]

Putting the list in here for now so I can avoid making ~20 issues at once

OS utilities (mostly):

• fdopendir
• realpath
• mkstemp
• system
• tmpfile
• tmpnam
• freopen

Wide character:

• towupper
• towlower

Wide file: (PRs in progress, see #196167)

• getwc
• ungetwc
• fputwc
• fgetwc
• fgetws
• fputws
• fwide

Wide formatting:

• fwprintf
• vfwprintf
• swprintf
• vswprintf
• fwscanf
• vfwscanf
• swscanf
• vswscanf

Threading:

• Various stuff, see https://discourse.llvm.org/t/building-libcxx-with-llvms-libc/90657/ for discussion

Misc:

• mblen should go in stdlib not wchar.
• fpos_t
• Fix __dso_handle setup in the libcxx tests (seems like it should be defined in crtbegin.o, which is being excluded due to -nostartfiles which is added here: libcxx/test/configs/llvm-libc++-llvm-libc.cfg.in

------------------ low priority for unblocking libcxx below here ------------------
Math:

• lgamma_r
• tgamma
• cosh
• sinh
• (various long double math functions)
• HUGE_VALL (macro)

Wide string manipulation:

• wcstoimax
• wcstoumax
• wctrans
• towctrans

uchar:

• mbrtoc16
• c16rtomb
• mbrtoc32