> On 14 Feb 2018, at 14:35, Christophe Fergeau <cferg...@redhat.com> wrote:
> 
> This one sounds more like an RFC to me

Well, this is really a bug fix in the documentation more than a RFC.

> , as from a quick look in server/,
> this is not the style currently in use.

As I pointed out in earlier discussions, this section of the style guide, as 
written currently, is mostly backwards compared to industry best practices.

Most projects today put project headers first for a reason: it catches the 
frequent case where a header change makes it not self-contained (therefore 
making it possible to break third-party code using that header).

Examples of explicit recommendations to that effect from various heavyweights:

1. LLVM: https://llvm.org/docs/CodingStandards.html:
> 
> We prefer these #includes to be listed in this order:
> 
>       • Main Module Header
>       • Local/Private Headers
>       • LLVM project/subproject headers (clang/..., lldb/..., llvm/..., etc)
>       • System #includes
> 


2. Google: 
https://google.github.io/styleguide/cppguide.html#Names_and_Order_of_Includes

> In dir/foo.cc or dir/foo_test.cc, whose main purpose is to implement or test 
> the stuff in dir2/foo2.h, order your includes as follows:
> 
>       • dir2/foo2.h.
>       • C system files.
>       • C++ system files.
>       • Other libraries' .h files.
>       • Your project's .h files.
> With the preferred ordering, if dir2/foo2.h omits any necessary includes, the 
> build of dir/foo.cc or dir/foo_test.cc will break. Thus, this rule ensures 
> that build breaks show up first for the people working on these files, not 
> for innocent people in other packages.
> 


3. Mozilla: 
https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Coding_Style#CC_practices
>       • Includes are split into three blocks, and sorted alphabetically in 
> each block:
>               • The main header: #include "Foo.h" in Foo.cpp
>               • Standard library includes: #include <map>
>               • Mozilla includes: #include "mozilla/dom/Element.h”



I prefer the LLVM order personally, because it tends to catch errors slightly 
faster and with a little less noise in the middle (system headers being assumed 
“good”).

For example, let’s say I forget a closing } in a namespace in 
frame-capture.hpp. With the proposed order, the error message is:

—————— 8< ————————————————————————
spice-streaming-agent.cpp:562:2: error: expected '}'
}
 ^
../include/spice-streaming-agent/frame-capture.hpp:13:17: note: to match this 
'{'
namespace spice {
—————— 8< ————————————————————————


With the current order or the Google order, the error message is:
 
—————— 8< ————————————————————————

In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:535:35:
 error: unknown class name 'false_type'; did you mean '::std::false_type'?
struct __is_tree_value_type_imp : false_type {};
                                  ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:526:38:
 note: '::std::false_type' declared here
typedef _LIBCPP_BOOL_CONSTANT(false) false_type;
                                     ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:538:63:
 error: unknown class name 'true_type'; did you mean '::std::true_type'?
struct __is_tree_value_type_imp<__value_type<_Key, _Value>> : true_type {};
                                                              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:525:38:
 note: '::std::true_type' declared here
typedef _LIBCPP_BOOL_CONSTANT(true)  true_type;
                                     ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:541:31:
 error: unknown class name 'false_type'; did you mean '::std::false_type'?
struct __is_tree_value_type : false_type {};
                              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:526:38:
 note: '::std::false_type' declared here
typedef _LIBCPP_BOOL_CONSTANT(false) false_type;
                                     ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:544:71:
 error: no template named '__uncvref'; did you mean '::std::__uncvref'?
struct __is_tree_value_type<_One> : __is_tree_value_type_imp<typename 
__uncvref<_One>::type> {};
                                                                      ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1121:8:
 note: '::std::__uncvref' declared here
struct __uncvref  {
       ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:564:12:
 error: no member named 'addressof' in namespace 'spice::std::__1'; did you 
mean '::std::addressof'?
    return _VSTD::addressof(__n);
           ^~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__config:392:15:
 note: expanded from macro '_VSTD'
#define _VSTD std::_LIBCPP_NAMESPACE
              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:434:1:
 note: '::std::addressof' declared here
addressof(_Tp& __x) _NOEXCEPT
^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:570:12:
 error: no member named 'move' in namespace 'spice::std::__1'; did you mean 
'::std::move'?
    return _VSTD::move(__v);
           ^~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__config:392:15:
 note: expanded from macro '_VSTD'
#define _VSTD std::_LIBCPP_NAMESPACE
              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:2178:1:
 note: '::std::move' declared here
move(_Tp&& __t) _NOEXCEPT
^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:580:11:
 error: no template named 'pair'; did you mean '::std::pair'?
  typedef pair<const _Key, _Tp>                        __container_value_type;
          ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/utility:309:29:
 note: '::std::pair' declared here
struct _LIBCPP_TEMPLATE_VIS pair
                            ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:581:11:
 error: no template named 'pair'; did you mean '::std::pair'?
  typedef pair<_Key, _Tp>                              __nc_value_type;
          ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/utility:309:29:
 note: '::std::pair' declared here
struct _LIBCPP_TEMPLATE_VIS pair
                            ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:593:19:
 error: no template named 'enable_if'; did you mean '::std::enable_if'?
  static typename enable_if<__is_same_uncvref<_Up, 
__container_value_type>::value,
                  ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:420:63:
 note: '::std::enable_if' declared here
template <bool, class _Tp = void> struct _LIBCPP_TEMPLATE_VIS enable_if {};
                                                              ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:593:29:
 error: no template named '__is_same_uncvref'; did you mean 
'::std::__is_same_uncvref'?
  static typename enable_if<__is_same_uncvref<_Up, 
__container_value_type>::value,
                            ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1138:8:
 note: '::std::__is_same_uncvref' declared here
struct __is_same_uncvref : is_same<typename __uncvref<_Tp>::type,
       ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:607:19:
 error: no template named 'enable_if'; did you mean '::std::enable_if'?
  static typename enable_if<__is_same_uncvref<_Up, 
__container_value_type>::value,
                  ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:420:63:
 note: '::std::enable_if' declared here
template <bool, class _Tp = void> struct _LIBCPP_TEMPLATE_VIS enable_if {};
                                                              ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:607:29:
 error: no template named '__is_same_uncvref'; did you mean 
'::std::__is_same_uncvref'?
  static typename enable_if<__is_same_uncvref<_Up, 
__container_value_type>::value,
                            ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:1138:8:
 note: '::std::__is_same_uncvref' declared here
struct __is_same_uncvref : is_same<typename __uncvref<_Tp>::type,
       ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:615:12:
 error: no member named 'addressof' in namespace 'spice::std::__1'; did you 
mean '::std::addressof'?
    return _VSTD::addressof(__n.__cc);
           ^~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__config:392:15:
 note: expanded from macro '_VSTD'
#define _VSTD std::_LIBCPP_NAMESPACE
              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:434:1:
 note: '::std::addressof' declared here
addressof(_Tp& __x) _NOEXCEPT
^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:621:12:
 error: no member named 'move' in namespace 'spice::std::__1'; did you mean 
'::std::move'?
    return _VSTD::move(__v.__nc);
           ^~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__config:392:15:
 note: expanded from macro '_VSTD'
#define _VSTD std::_LIBCPP_NAMESPACE
              ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:2178:1:
 note: '::std::move' declared here
move(_Tp&& __t) _NOEXCEPT
^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:631:20:
 error: no template named '__rebind_pointer'; did you mean 
'::std::__rebind_pointer'?
  typedef typename __rebind_pointer<_VoidPtr, __node_base_type>::type
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory:974:8:
 note: '::std::__rebind_pointer' declared here
struct __rebind_pointer {
       ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:635:20:
 error: no template named '__rebind_pointer'; did you mean 
'::std::__rebind_pointer'?
  typedef typename __rebind_pointer<_VoidPtr, __end_node_type>::type
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/memory:974:8:
 note: '::std::__rebind_pointer' declared here
struct __rebind_pointer {
       ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:640:20:
 error: no template named 'conditional'; did you mean '::std::conditional'?
  typedef typename conditional<
                   ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:409:33:
 note: '::std::conditional' declared here
    struct _LIBCPP_TEMPLATE_VIS conditional {typedef _If type;};
                                ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:641:7:
 error: no template named 'is_pointer'; did you mean '::std::is_pointer'?
      is_pointer<__end_node_pointer>::value,
      ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:747:50:
 note: '::std::is_pointer' declared here
template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pointer
                                                 ^
In file included from spice-streaming-agent.cpp:38:
In file included from ./concrete-agent.hpp:10:
In file included from 
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/set:389:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/__tree:647:18:
 error: no template named 'is_same'; did you mean '::std::is_same'?
  static_assert((is_same<typename pointer_traits<_VoidPtr>::element_type, 
void>::value),
                 ^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/type_traits:828:61:
 note: '::std::is_same' declared here
template <class _Tp, class _Up> struct _LIBCPP_TEMPLATE_VIS is_same           : 
public false_type {};
                                                            ^
fatal error: too many errors emitted, stopping now [-ferror-limit=]
—————— 8< ————————————————————————


Thanks
Christophe

> 
> Christophe
> 
> On Thu, Feb 08, 2018 at 12:25:31PM +0100, Christophe de Dinechin wrote:
>> From: Christophe de Dinechin <dinec...@redhat.com>
>> 
>> As written, the headers style guide looks quite wrong. In particular,
>> it places headers in an order that makes it hard to detect hidden
>> dependencies in SPICE headers.
>> 
>> These rules can be enforced by the .clang-format proposed in earlier patch,
>> locally if you use the Emacs clang-format.el integration supplied with LLVM.
>> 
>> Signed-off-by: Christophe de Dinechin <dinec...@redhat.com>
>> ---
>> docs/spice_style.txt | 44 +++++++++++++++++++++++++++++---------------
>> 1 file changed, 29 insertions(+), 15 deletions(-)
>> 
>> diff --git a/docs/spice_style.txt b/docs/spice_style.txt
>> index 108a57a5..ff505b2a 100644
>> --- a/docs/spice_style.txt
>> +++ b/docs/spice_style.txt
>> @@ -407,34 +407,48 @@ Historically, some headers added underscores 
>> liberally, e.g. MY_MODULE_H_. This
>> Header inclusion
>> ----------------
>> 
>> -Headers should be included in this order
>> +Headers should be included in this order:
>> +- config.h, which should only be included from C source files
>> +- [module].h, where [module].c is the corresponding implementation file
>> +- [module]-xyz.h, which are support headers for [module]
>> +- Other application headers, using #include "file.h"
>> +- System headers, using #include <file.h>
>> +- If necessary, C++ system headers, using #include <file>
>> +
>> +This order is designed to maximize chances of catching missing headers in 
>> headers (i.e. headers that are not self-contained).
>> +
>> +In summary, Headers should be included in this order
>> 
>> [source,c]
>> ----
>> -#include <system_headers.h>
>> -#include <no_spice_no_system_libraries.h>
>> +#include "config.h"
>> +#include "source.h"
>> +#include "source-support.h"
>> +#include "some-other-source.h"
>> +
>> #include <spice_protocol.h>
>> #include <spice_common.h>
>> -
>> -#include "spice_server.h"
>> +#include <no_spice_no_system_libraries.h>
>> +#include <system_headers.h>
>> +#include <vector>
>> +#include <cstdio>
>> ----
>> 
>> -(note the empty line between no spice-server and spice-server headers)
>> +(note the empty line between application headers included with "" and 
>> system headers included with <>
>> 
>> -Also in source (no header) files you must include `config.h` at the 
>> beginning so should start (beside comments and copyright) with
>> +Headers should include only the headers required to process the header 
>> itself, and otherwise include as little as possible.
>> 
>> [source,c]
>> ----
>> -#ifdef HAVE_CONFIG_H
>> -#include <config.h>
>> -#endif
>> +#ifndef SOURCE_H
>> +#define SOURCE_H
>> +#include "application-header-required-for-header.h"
>> 
>> -#include <system_headers.h>
>> -#include <no_spice_no_system_libraries.h>
>> -#include <spice_protocol.h>
>> -#include <spice_common.h>
>> +#include <system-header-required-for-header.h>
>> +
>> +...
>> 
>> -#include "spice_server.h"
>> +#endif /* SOURCE_H */
>> ----
>> 
>> 
>> -- 
>> 2.13.5 (Apple Git-94)
>> 
>> _______________________________________________
>> Spice-devel mailing list
>> Spice-devel@lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/spice-devel
> _______________________________________________
> Spice-devel mailing list
> Spice-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/spice-devel

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