Re: [PATCH 2/2] osdep: protect qemu/osdep.h with extern "C"

[Peter Maydell]

On Tue, 13 Apr 2021 at 12:37, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> System headers may include templates if compiled with a C++ compiler,
> which cause the compiler to complain if qemu/osdep.h is included
> within a C++ source file's 'extern "C"' block.  Add
> an 'extern "C"' block directly to qemu/osdep.h, so that
> system headers can be kept out of it.
>
> There is a stray declaration early in qemu/osdep.h, which needs
> to be special cased.  Add a definition in qemu/compiler.h to
> make it look nice.
>
> config-host.h, CONFIG_TARGET, exec/poison.h and qemu/compiler.h
> are included outside the 'extern "C"' block; that is not
> an issue because they consist entirely of preprocessor directives.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  disas/nanomips.cpp      |  2 +-
>  include/qemu/compiler.h |  6 ++++++
>  include/qemu/osdep.h    | 10 +++++++++-
>  3 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/disas/nanomips.cpp b/disas/nanomips.cpp
> index 2b09655271..8ddef897f0 100644
> --- a/disas/nanomips.cpp
> +++ b/disas/nanomips.cpp
> @@ -27,8 +27,8 @@
>   *      Reference Manual", Revision 01.01, April 27, 2018
>   */
>
> -extern "C" {
>  #include "qemu/osdep.h"
> +extern "C" {
>  #include "disas/dis-asm.h"
>  }
>
> diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
> index cf28bb2bcd..091c45248b 100644
> --- a/include/qemu/compiler.h
> +++ b/include/qemu/compiler.h
> @@ -11,6 +11,12 @@
>  #define QEMU_STATIC_ANALYSIS 1
>  #endif
>
> +#ifdef __cplusplus
> +#define QEMU_EXTERN_C extern "C"
> +#else
> +#define QEMU_EXTERN_C extern
> +#endif
> +
>  #define QEMU_NORETURN __attribute__ ((__noreturn__))
>
>  #define QEMU_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index b67b0a1e8c..3f8785a471 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -57,7 +57,7 @@
>  #define daemon qemu_fake_daemon_function
>  #include <stdlib.h>
>  #undef daemon
> -extern int daemon(int, int);
> +QEMU_EXTERN_C int daemon(int, int);
>  #endif
>
>  #ifdef _WIN32
> @@ -113,6 +113,10 @@ extern int daemon(int, int);
>
>  #include "glib-compat.h"
>
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
>  #ifdef _WIN32
>  #include "sysemu/os-win32.h"
>  #endif

There are some system header includes in osdep.h below this point
(sys/shm.h and sys/uio.h) -- don't they need to be moved up
to go with the other system includes first ?

thanks
-- PMM