[all-commits] [llvm/llvm-project] 7e3ea5: [clang-tidy] modernize-deprecated-headers check sh...

[Balazs Benics via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7e3ea55da88a9d7feaa22f29d51f89fd0152a189
      https://github.com/llvm/llvm-project/commit/7e3ea55da88a9d7feaa22f29d51f89fd0152a189
  Author: Balazs Benics <balazs.benics at sigmatechnology.se>
  Date:   2022-05-13 (Fri, 13 May 2022)

  Changed paths:
    M clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.cpp
    M clang-tools-extra/clang-tidy/modernize/DeprecatedHeadersCheck.h
    M clang-tools-extra/docs/ReleaseNotes.rst
    A clang-tools-extra/test/clang-tidy/checkers/Inputs/modernize-deprecated-headers/mylib.h
    A clang-tools-extra/test/clang-tidy/checkers/modernize-deprecated-headers-extern-c.cpp

  Log Message:
  -----------
  [clang-tidy] modernize-deprecated-headers check should respect extern "C" blocks

The check should not report includes wrapped by `extern "C" { ... }` blocks,
such as:

```lang=C++
#ifdef __cplusplus
extern "C" {
#endif

#include "assert.h"

#ifdef __cplusplus
}
#endif
```

This pattern comes up sometimes in header files designed to be consumed
by both C and C++ source files.
The check now reports false reports when the header file is consumed by
a C++ translation unit.

In this change, I'm not emitting the reports immediately from the
`PPCallback`, rather aggregating them for further processing.
After all preprocessing is done, the matcher will be called on the
`TranslationUnitDecl`, ensuring that the check callback is called only
once.

Within that callback, I'm recursively visiting each decls, looking for
`LinkageSpecDecls` which represent the `extern "C"` specifier.
After this, I'm dropping all the reports coming from inside of it.
After the visitation is done, I'm emitting the reports I'm left with.

For performance reasons, I'm sorting the `IncludeMarkers` by their
corresponding locations.
This makes the scan `O(log(N)` when looking up the `IncludeMarkers`
affected by the given `extern "C"` block. For this, I'm using
`lower_bound()` and `upper_bound()`.

Reviewed By: whisperity

Differential Revision: https://reviews.llvm.org/D125209