[PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

[PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

[Paolo Bonzini]

qemu/osdep.h is quite special in that, despite being part of QEMU sources,
it is included by C++ source files as well.

disas/nanomips.cpp is doing so within an 'extern "C"' block, which breaks
with latest glib due to the inclusion of templates in glib.h.

These patches implement Daniel Berrangé's idea of pushing the 'extern "C"'
block within glib.h and including system headers (including glib.h,
and in fact QEMU's own glib-compat.h too) *outside* the block.

(CI has not finished running yet, but it seems encouraging).

Paolo

Paolo Bonzini (2):
  osdep: include glib-compat.h before other QEMU headers
  osdep: protect qemu/osdep.h with extern "C"

 disas/nanomips.cpp      |  2 +-
 include/qemu/compiler.h |  6 ++++++
 include/qemu/osdep.h    | 13 +++++++++++--
 3 files changed, 18 insertions(+), 3 deletions(-)

-- 
2.30.1

[PATCH 1/2] osdep: include glib-compat.h before other QEMU headers

[Paolo Bonzini]

glib-compat.h is sort of like a system header, and it needs to include
system headers (glib.h) that may dislike being included under
'extern "C"'.  Move it right after all system headers and before
all other QEMU headers.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/osdep.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index ba15be9c56..b67b0a1e8c 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -111,6 +111,8 @@ extern int daemon(int, int);
 #define WEXITSTATUS(x) (x)
 #endif
 
+#include "glib-compat.h"
+
 #ifdef _WIN32
 #include "sysemu/os-win32.h"
 #endif
@@ -123,7 +125,6 @@ extern int daemon(int, int);
 #include <AvailabilityMacros.h>
 #endif
 
-#include "glib-compat.h"
 #include "qemu/typedefs.h"
 
 /*
-- 
2.30.1

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

[Paolo Bonzini]

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
@@ -723,4 +727,8 @@ static inline int platform_does_not_support_system(const char *command)
 }
 #endif /* !HAVE_SYSTEM_FUNCTION */
 
+#ifdef __cplusplus
+}
+#endif
+
 #endif
-- 
2.30.1

Re: [PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

[no-reply]

Patchew URL: https://patchew.org/QEMU/20210413113741.214867-1-pbonzini@redhat.com/



Hi,

This series seems to have some coding style problems. See output below for
more information:

Type: series
Message-id: 20210413113741.214867-1-pbonzini@redhat.com
Subject: [PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

=== TEST SCRIPT BEGIN ===
#!/bin/bash
git rev-parse base > /dev/null || exit 0
git config --local diff.renamelimit 0
git config --local diff.renames True
git config --local diff.algorithm histogram
./scripts/checkpatch.pl --mailback base..
=== TEST SCRIPT END ===

Updating 3c8cf5a9c21ff8782164d1def7f44bd888713384
From https://github.com/patchew-project/qemu
 - [tag update]      patchew/20210408195534.647895-1-antonkuchin@yandex-team.ru -> patchew/20210408195534.647895-1-antonkuchin@yandex-team.ru
 * [new tag]         patchew/20210413113741.214867-1-pbonzini@redhat.com -> patchew/20210413113741.214867-1-pbonzini@redhat.com
Switched to a new branch 'test'
992fa52 osdep: protect qemu/osdep.h with extern "C"
bc2310f osdep: include glib-compat.h before other QEMU headers

=== OUTPUT BEGIN ===
1/2 Checking commit bc2310f731a5 (osdep: include glib-compat.h before other QEMU headers)
2/2 Checking commit 992fa52da413 (osdep: protect qemu/osdep.h with extern "C")
WARNING: architecture specific defines should be avoided
#51: FILE: include/qemu/compiler.h:14:
+#ifdef __cplusplus

ERROR: storage class should be at the beginning of the declaration
#52: FILE: include/qemu/compiler.h:15:
+#define QEMU_EXTERN_C extern "C"

ERROR: storage class should be at the beginning of the declaration
#54: FILE: include/qemu/compiler.h:17:
+#define QEMU_EXTERN_C extern

WARNING: architecture specific defines should be avoided
#77: FILE: include/qemu/osdep.h:116:
+#ifdef __cplusplus

WARNING: architecture specific defines should be avoided
#88: FILE: include/qemu/osdep.h:730:
+#ifdef __cplusplus

total: 2 errors, 3 warnings, 47 lines checked

Patch 2/2 has style problems, please review.  If any of these errors
are false positives report them to the maintainer, see
CHECKPATCH in MAINTAINERS.

=== OUTPUT END ===

Test command exited with code: 1


The full log is available at
http://patchew.org/logs/20210413113741.214867-1-pbonzini@redhat.com/testing.checkpatch/?type=message.
---
Email generated automatically by Patchew [https://patchew.org/].
Please send your feedback to patchew-devel@redhat.com

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

Re: [PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

[Philippe Mathieu-Daudé]

Cc'ing MediaTek reviewers.

On 4/13/21 1:37 PM, Paolo Bonzini wrote:
> qemu/osdep.h is quite special in that, despite being part of QEMU sources,
> it is included by C++ source files as well.
> 
> disas/nanomips.cpp is doing so within an 'extern "C"' block, which breaks
> with latest glib due to the inclusion of templates in glib.h.
> 
> These patches implement Daniel Berrangé's idea of pushing the 'extern "C"'
> block within glib.h and including system headers (including glib.h,
> and in fact QEMU's own glib-compat.h too) *outside* the block.
> 
> (CI has not finished running yet, but it seems encouraging).
> 
> Paolo
> 
> Paolo Bonzini (2):
>   osdep: include glib-compat.h before other QEMU headers
>   osdep: protect qemu/osdep.h with extern "C"
> 
>  disas/nanomips.cpp      |  2 +-
>  include/qemu/compiler.h |  6 ++++++
>  include/qemu/osdep.h    | 13 +++++++++++--
>  3 files changed, 18 insertions(+), 3 deletions(-)
> 

Re: [PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

[Aleksandar Rikalo]

[-- Attachment #1: Type: text/plain, Size: 2737 bytes --]

Hi Paolo,

Can you specify how to reproduce the issue ? We need more details about environment.

In my case, everything seems to work fine for the newest version of glib (2.68).

Thank you,
Aleksandar

> qemu/osdep.h is quite special in that, despite being part of QEMU sources,
> it is included by C++ source files as well.
>
> disas/nanomips.cpp is doing so within an 'extern "C"' block, which breaks
> with latest glib due to the inclusion of templates in glib.h.
>
> These patches implement Daniel Berrangé's idea of pushing the 'extern "C"'
> block within glib.h and including system headers (including glib.h,
> and in fact QEMU's own glib-compat.h too) *outside* the block.
>
> (CI has not finished running yet, but it seems encouraging).
>
> Paolo
>
> Paolo Bonzini (2):
>   osdep: include glib-compat.h before other QEMU headers
>   osdep: protect qemu/osdep.h with extern "C"
>
>  disas/nanomips.cpp      |  2 +-
>  include/qemu/compiler.h |  6 ++++++
>  include/qemu/osdep.h    | 13 +++++++++++--
>  3 files changed, 18 insertions(+), 3 deletions(-)
>
> --
> 2.30.1
________________________________
From: Philippe Mathieu-Daudé <philippe.mathieu.daude@gmail.com> on behalf of Philippe Mathieu-Daudé <f4bug@amsat.org>
Sent: Tuesday, April 13, 2021 5:58 PM
To: Paolo Bonzini <pbonzini@redhat.com>; qemu-devel@nongnu.org <qemu-devel@nongnu.org>
Cc: peter.maydell@linaro.org <peter.maydell@linaro.org>; berrange@redhat.com <berrange@redhat.com>; Aleksandar Rikalo <Aleksandar.Rikalo@syrmia.com>; Vince.DelVecchio@mediatek.com <Vince.DelVecchio@mediatek.com>; Petar Jovanovic <petar.jovanovic@syrmia.com>; Filip Vidojevic <Filip.Vidojevic@Syrmia.com>
Subject: Re: [PATCH 0/2] osdep: allow including qemu/osdep.h outside extern "C"

Cc'ing MediaTek reviewers.

On 4/13/21 1:37 PM, Paolo Bonzini wrote:
> qemu/osdep.h is quite special in that, despite being part of QEMU sources,
> it is included by C++ source files as well.
>
> disas/nanomips.cpp is doing so within an 'extern "C"' block, which breaks
> with latest glib due to the inclusion of templates in glib.h.
>
> These patches implement Daniel Berrangé's idea of pushing the 'extern "C"'
> block within glib.h and including system headers (including glib.h,
> and in fact QEMU's own glib-compat.h too) *outside* the block.
>
> (CI has not finished running yet, but it seems encouraging).
>
> Paolo
>
> Paolo Bonzini (2):
>   osdep: include glib-compat.h before other QEMU headers
>   osdep: protect qemu/osdep.h with extern "C"
>
>  disas/nanomips.cpp      |  2 +-
>  include/qemu/compiler.h |  6 ++++++
>  include/qemu/osdep.h    | 13 +++++++++++--
>  3 files changed, 18 insertions(+), 3 deletions(-)
>


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