[libc] Fix accidental inclusion of system libc headers.
authorPaula Toth <paulatoth@google.com>
Thu, 21 May 2020 08:21:07 +0000 (01:21 -0700)
committerPaula Toth <paulatoth@google.com>
Thu, 21 May 2020 08:21:37 +0000 (01:21 -0700)
commitb2a485e37edf6415701c472d93afa7fa26dbcccb
tree321dfada318b997dcbede602394517cd67830957
parentdedcefe09d18f1e9d60336541fb6ad03dae551ba
[libc] Fix accidental inclusion of system libc headers.

Summary:
I found that because `--system-headers` flag was not included when running clang-tidy, errors produced from compiler provided headers were being suppressed. After passing this flag I realized that by including headers like stdint.h we were indirectly including headers from the system libc. To prevent this we pass `-ffreestanding`.
We don't want to pass `--system-headers` for all checks just the `llvmlibc-restrict-system-libc-headers` therefore we do a separate invocation of clang-tidy for this check.

Reviewers: abrachet, sivachandra

Reviewed By: sivachandra

Subscribers: mgorny, aheejin, tschuett, ecnelises, libc-commits

Tags: #libc-project

Differential Revision: https://reviews.llvm.org/D80178
libc/cmake/modules/LLVMLibCObjectRules.cmake
libc/src/.clang-tidy