[libcxx-commits] [PATCH] D131441: [libc++] Diagnose when header search paths are set up incorrectly

[Louis Dionne via Phabricator via libcxx-commits]

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An issue I often see in codebases compiled for unusual platforms is
that header search paths are specified manually and are subtly wrong.
For example, people will manually add `-isystem <some-toolchain>/usr/include`,
which ends up messing up the layering of header search paths required by
libc++ (because the C Standard Library now appears *before* libc++ in
the search paths). Without this patch, this will end up causing
compilation errors that are pretty inscrutable. This patch aims to
improve the user experience by diagnosing this issue explicitly.

In all cases I can think of, I would expect that a compilation error
occur if these header search paths are not layered properly. This
should only provide an explicit diagnostic instead of failing due
to seemingly unrelated compilation errors.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D131441

Files:
  libcxx/include/cctype
  libcxx/include/cerrno
  libcxx/include/cfenv
  libcxx/include/cfloat
  libcxx/include/cinttypes
  libcxx/include/climits
  libcxx/include/clocale
  libcxx/include/cmath
  libcxx/include/csetjmp
  libcxx/include/cstddef
  libcxx/include/cstdint
  libcxx/include/cstdio
  libcxx/include/cstdlib
  libcxx/include/cstring
  libcxx/include/cuchar
  libcxx/include/cwchar
  libcxx/include/cwctype

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