modernize-deprecated-headers¶

Some headers from C library were deprecated in C++ and are no longer welcome in C++ codebases. Some have no effect in C++. For more details refer to the C++14 Standard [depr.c.headers] section.

This check replaces C standard library headers with their C++ alternatives and removes redundant ones.

// C++ source file...
#include <assert.h>
#include <stdbool.h>

// becomes

#include <cassert>
// No 'stdbool.h' here.

Important note: the Standard doesn’t guarantee that the C++ headers declare all the same functions in the global namespace. The check in its current form can break the code that uses library symbols from the global namespace.

<assert.h>
<complex.h>
<ctype.h>
<errno.h>
<fenv.h> // deprecated since C++11
<float.h>
<inttypes.h>
<limits.h>
<locale.h>
<math.h>
<setjmp.h>
<signal.h>
<stdarg.h>
<stddef.h>
<stdint.h>
<stdio.h>
<stdlib.h>
<string.h>
<tgmath.h> // deprecated since C++11
<time.h>
<uchar.h> // deprecated since C++11
<wchar.h>
<wctype.h>

If the specified standard is older than C++11 the check will only replace headers deprecated before C++11, otherwise – every header that appeared in the previous list.

These headers don’t have effect in C++:

<iso646.h>
<stdalign.h>
<stdbool.h>

The check ignores include directives within extern "C" { ... } blocks, since a library might want to expose some API for C and C++ libraries.

// C++ source file...
extern "C" {
#include <assert.h>  // Left intact.
#include <stdbool.h> // Left intact.
}

Options¶

CheckHeaderFile¶: clang-tidy cannot know if the header file included by the currently analyzed C++ source file is not included by any other C source files. Hence, to omit false-positives and wrong fixit-hints, we ignore emitting reports into header files. One can set this option to true if they know that the header files in the project are only used by C++ source files. Default is false.