GeneralPurpose-LinkageMismatch

Do not include C header files into C++ without ‘extern “C”’

Required inputs: IR

Declarations included in C and C++ (without extern "C") may have incompatible meanings, i.e. functions have different calling conventions.

Bad code (mixed linkage):

// foo.h
int foo(int);  // ERROR: This declaration has different meanings in C and C++
               // (name mangling used only when included from C++)

// foo.cpp
#include "foo.h"

// foo.c
#include "foo.h"

Good code:

// foo.h
#ifdef __cplusplus
extern "C" {
#endif
int foo(int);  // OK: extern "C" ensures that this declaration has the same meaning
               // in C and C++
#ifdef __cplusplus
}
#endif

Good code:

// foo.h
int foo(int);

// foo.cpp
extern "C" {
    // OK: extern "C" ensures that this declaration has the same meaning in C and C++
    #include "foo.h"
}

// foo.c
#include "foo.h"

Possible Messages

Key	Text	Severity	Disabled
linkage_mismatch	This declaration has different meanings in C and C++ (name mangling used only when included from C++. Did you forget to add ‘extern “C”’ when including C headers into C++?	None	False

Options

• This rule shares the following common options: exclude_in_macros, exclude_messages_in_system_headers, excludes, extend_exclude_to_macro_invocations, includes, justification_checker, languages, post_processing, provider, report_at, severity

• The following places define options that affect this rule: Stylechecks, Analysis-GlobalOptions

• This rule has no individual options.