[Buildroot] [PATCH] package/racehound: fix comment

[Buildroot] [PATCH] package/racehound: fix comment

[Yann E. MORIN]

racehound requires a kernel >= 3.14 to be built and to run.

However, the current conditions on the corresponding comments are wrong:
  - the comment about the kernel has a dependency on the requested
    headers
  - the comment on the toolchain features does not have this condition.

Thus, the comments are not shown/hidden under the appropriate
conditions, like in this situation:
  - toolchain with headers < 3.14 (e.g. Sourcery CodeBench x86/x86_64
    2012.09 with headers 3.5)
  - kernel 4.5 enabled

this comment is shown:
    racehound needs an Linux kernel >= 3.14 to be built

So, this is incorrect, because:
 1- a kernel >= 3.14 is indeed to be built
 2- the headers version mismatch is not reported

Fix that by moving the dependency on the kernel headers to the
appropriate comment and enhance it.

Since there is no way we can know the kernel version to be built, we can
not add such a condition; still, we leave the kernel message as-is.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
---
 package/racehound/Config.in | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/package/racehound/Config.in b/package/racehound/Config.in
index 9f1011b..53e39a8 100644
--- a/package/racehound/Config.in
+++ b/package/racehound/Config.in
@@ -27,10 +27,11 @@ config BR2_PACKAGE_RACEHOUND
 	  https://github.com/winnukem/racehound
 
 comment "racehound needs an Linux kernel >= 3.14 to be built"
-	depends on !BR2_LINUX_KERNEL || !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14
+	depends on !BR2_LINUX_KERNEL
 	depends on BR2_i386 || BR2_x86_64
 
-comment "racehound needs a uClibc or (e)glibc toolchain w/ C++, wchar, dynamic library"
+comment "racehound needs a uClibc or (e)glibc toolchain w/ C++, wchar, dynamic library, headers >= 3.14"
 	depends on BR2_i386 || BR2_x86_64
 	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || BR2_STATIC_LIBS \
-		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC)
+		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC) \
+		|| !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14
-- 
1.9.1

[Buildroot] [PATCH] package/racehound: fix comment

[Arnout Vandecappelle]

On 04/12/16 19:20, Yann E. MORIN wrote:
> racehound requires a kernel >= 3.14 to be built and to run.

  If I understand correctly, it actually doesn't need kernel headers >= 3.14, 
but only a kernel >= 3.14...

>
> However, the current conditions on the corresponding comments are wrong:
>    - the comment about the kernel has a dependency on the requested
>      headers
>    - the comment on the toolchain features does not have this condition.
>
> Thus, the comments are not shown/hidden under the appropriate
> conditions, like in this situation:
>    - toolchain with headers < 3.14 (e.g. Sourcery CodeBench x86/x86_64
>      2012.09 with headers 3.5)
>    - kernel 4.5 enabled

  So in this configuration, it should actually be possible to build racehound.

  If this is true, I would remove the dependency on kernel headers.

>
> this comment is shown:
>      racehound needs an Linux kernel >= 3.14 to be built

  But I would keep this comment if !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14, to make 
sure the user realizes that he needs a >= 3.14 kernel. He can still select the 
package if the headers ar < 3.14, so if he knows what he's doing it will be fine.

  Even better would be
	depends on !BR2_LINUX_KERNEL || \
		(BR2_PACKAGE_RACEHOUND && !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14)
i.e. only show the >= 3.14 warning in case you actually selected racehound.

>
> So, this is incorrect, because:
>   1- a kernel >= 3.14 is indeed to be built
>   2- the headers version mismatch is not reported
>
> Fix that by moving the dependency on the kernel headers to the
> appropriate comment and enhance it.
>
> Since there is no way we can know the kernel version to be built, we can
> not add such a condition; still, we leave the kernel message as-is.

  It can be tested in a pre-configure hook. But the cmake rules already check 
for that, so there's no need to do it again in buildroot.

>
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> ---
>   package/racehound/Config.in | 7 ++++---
>   1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/package/racehound/Config.in b/package/racehound/Config.in
> index 9f1011b..53e39a8 100644
> --- a/package/racehound/Config.in
> +++ b/package/racehound/Config.in
> @@ -27,10 +27,11 @@ config BR2_PACKAGE_RACEHOUND
>   	  https://github.com/winnukem/racehound
>
>   comment "racehound needs an Linux kernel >= 3.14 to be built"
> -	depends on !BR2_LINUX_KERNEL || !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14
> +	depends on !BR2_LINUX_KERNEL
>   	depends on BR2_i386 || BR2_x86_64
>
> -comment "racehound needs a uClibc or (e)glibc toolchain w/ C++, wchar, dynamic library"
> +comment "racehound needs a uClibc or (e)glibc toolchain w/ C++, wchar, dynamic library, headers >= 3.14"
>   	depends on BR2_i386 || BR2_x86_64
>   	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || BR2_STATIC_LIBS \
> -		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC)
> +		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC) \
> +		|| !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14

  Just to be clear: I think this comment shouldn't be changed at all.

  Assuming, of course, that my assumption is correct that it has no particular 
dependency on kernel headers.

  Regards,
  Arnout

>


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] package/racehound: fix comment

[Peter Korsgaard]

>>>>> "Yann" == Yann E MORIN <yann.morin.1998@free.fr> writes:

 > racehound requires a kernel >= 3.14 to be built and to run.
 > However, the current conditions on the corresponding comments are wrong:
 >   - the comment about the kernel has a dependency on the requested
 >     headers
 >   - the comment on the toolchain features does not have this condition.

 > Thus, the comments are not shown/hidden under the appropriate
 > conditions, like in this situation:
 >   - toolchain with headers < 3.14 (e.g. Sourcery CodeBench x86/x86_64
 >     2012.09 with headers 3.5)
 >   - kernel 4.5 enabled

 > this comment is shown:
 >     racehound needs an Linux kernel >= 3.14 to be built

 > So, this is incorrect, because:
 >  1- a kernel >= 3.14 is indeed to be built
 >  2- the headers version mismatch is not reported

 > Fix that by moving the dependency on the kernel headers to the
 > appropriate comment and enhance it.

 > Since there is no way we can know the kernel version to be built, we can
 > not add such a condition; still, we leave the kernel message as-is.

 > Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

Committed, thanks.

-- 
Bye, Peter Korsgaard

[Buildroot] [PATCH] package/racehound: fix comment

[Peter Korsgaard]

>>>>> "Arnout" == Arnout Vandecappelle <arnout@mind.be> writes:

 > On 04/12/16 19:20, Yann E. MORIN wrote:
 >> racehound requires a kernel >= 3.14 to be built and to run.

 >  If I understand correctly, it actually doesn't need kernel headers >=
 > 3.14, but only a kernel >= 3.14...

Ups, sorry - I somehow missed your mail until after applying and pushing
Yanns change. Lets see what Yann says.

-- 
Bye, Peter Korsgaard

[Buildroot] [PATCH] package/racehound: fix comment

[Arnout Vandecappelle]

On 04/13/16 00:00, Peter Korsgaard wrote:
>>>>>> "Yann" == Yann E MORIN <yann.morin.1998@free.fr> writes:
>
>   > racehound requires a kernel >= 3.14 to be built and to run.
>   > However, the current conditions on the corresponding comments are wrong:
>   >   - the comment about the kernel has a dependency on the requested
>   >     headers
>   >   - the comment on the toolchain features does not have this condition.
>
>   > Thus, the comments are not shown/hidden under the appropriate
>   > conditions, like in this situation:
>   >   - toolchain with headers < 3.14 (e.g. Sourcery CodeBench x86/x86_64
>   >     2012.09 with headers 3.5)
>   >   - kernel 4.5 enabled
>
>   > this comment is shown:
>   >     racehound needs an Linux kernel >= 3.14 to be built
>
>   > So, this is incorrect, because:
>   >  1- a kernel >= 3.14 is indeed to be built
>   >  2- the headers version mismatch is not reported
>
>   > Fix that by moving the dependency on the kernel headers to the
>   > appropriate comment and enhance it.
>
>   > Since there is no way we can know the kernel version to be built, we can
>   > not add such a condition; still, we leave the kernel message as-is.
>
>   > Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
>
> Committed, thanks.

  So, you don't agree with my analysis? :-)

  Regards,
  Arnout


-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] package/racehound: fix comment

[Yann E. MORIN]

Arnout, All,

On 2016-04-12 23:27 +0200, Arnout Vandecappelle spake thusly:
> On 04/12/16 19:20, Yann E. MORIN wrote:
> >racehound requires a kernel >= 3.14 to be built and to run.
> 
>  If I understand correctly, it actually doesn't need kernel headers >= 3.14,
> but only a kernel >= 3.14...

Indeed, the dependency on headerrs >= 3.14 is wrong.

I'll send an updated patch to fix that.

> >However, the current conditions on the corresponding comments are wrong:
> >   - the comment about the kernel has a dependency on the requested
> >     headers
> >   - the comment on the toolchain features does not have this condition.
> >
> >Thus, the comments are not shown/hidden under the appropriate
> >conditions, like in this situation:
> >   - toolchain with headers < 3.14 (e.g. Sourcery CodeBench x86/x86_64
> >     2012.09 with headers 3.5)
> >   - kernel 4.5 enabled
> 
>  So in this configuration, it should actually be possible to build racehound.
>  If this is true, I would remove the dependency on kernel headers.

I just checked those configurations:
  - headers 3.14, kernel 4.5 => OK
  - headers 3.5, kernel 4.5  => OK

> >this comment is shown:
> >     racehound needs an Linux kernel >= 3.14 to be built
> 
>  But I would keep this comment if !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14, to
> make sure the user realizes that he needs a >= 3.14 kernel. He can still
> select the package if the headers ar < 3.14, so if he knows what he's doing
> it will be fine.

I respectfully disagree. There is no corelation between the headers and
the running kernel (except running kernel mnust be more recent than
headers).

Besides, this would be misleading in the other way: if headers are 3.14+
but kernel is 3.13-, the comment wouild not be shown.

>  Even better would be
> 	depends on !BR2_LINUX_KERNEL || \
> 		(BR2_PACKAGE_RACEHOUND && !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14)
> i.e. only show the >= 3.14 warning in case you actually selected racehound.

Again, headers_atl_least_X_Y does not represent the running kernel, so I
find it a bit misleading that we use that option to show/hide the
comment.

> >So, this is incorrect, because:
> >  1- a kernel >= 3.14 is indeed to be built
> >  2- the headers version mismatch is not reported
> >
> >Fix that by moving the dependency on the kernel headers to the
> >appropriate comment and enhance it.
> >
> >Since there is no way we can know the kernel version to be built, we can
> >not add such a condition; still, we leave the kernel message as-is.
> 
>  It can be tested in a pre-configure hook. But the cmake rules already check
> for that, so there's no need to do it again in buildroot.

No, it does not check for it since we pass it -DKERNEL_VERSION_OK=YES

Regards,
Yann E. MORIN.

> >Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> >---
> >  package/racehound/Config.in | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> >diff --git a/package/racehound/Config.in b/package/racehound/Config.in
> >index 9f1011b..53e39a8 100644
> >--- a/package/racehound/Config.in
> >+++ b/package/racehound/Config.in
> >@@ -27,10 +27,11 @@ config BR2_PACKAGE_RACEHOUND
> >  	  https://github.com/winnukem/racehound
> >
> >  comment "racehound needs an Linux kernel >= 3.14 to be built"
> >-	depends on !BR2_LINUX_KERNEL || !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14
> >+	depends on !BR2_LINUX_KERNEL
> >  	depends on BR2_i386 || BR2_x86_64
> >
> >-comment "racehound needs a uClibc or (e)glibc toolchain w/ C++, wchar, dynamic library"
> >+comment "racehound needs a uClibc or (e)glibc toolchain w/ C++, wchar, dynamic library, headers >= 3.14"
> >  	depends on BR2_i386 || BR2_x86_64
> >  	depends on !BR2_INSTALL_LIBSTDCPP || !BR2_USE_WCHAR || BR2_STATIC_LIBS \
> >-		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC)
> >+		|| !(BR2_TOOLCHAIN_USES_UCLIBC || BR2_TOOLCHAIN_USES_GLIBC) \
> >+		|| !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14
> 
>  Just to be clear: I think this comment shouldn't be changed at all.
> 
>  Assuming, of course, that my assumption is correct that it has no
> particular dependency on kernel headers.
> 
>  Regards,
>  Arnout
> 
> >
> 
> 
> -- 
> Arnout Vandecappelle                          arnout at mind be
> Senior Embedded Software Architect            +32-16-286500
> Essensium/Mind                                http://www.mind.be
> G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
> LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
> GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'

[Buildroot] [PATCH] package/racehound: fix comment

[Arnout Vandecappelle]

On 04/13/16 22:18, Yann E. MORIN wrote:
> Arnout, All,
>
> On 2016-04-12 23:27 +0200, Arnout Vandecappelle spake thusly:
>> On 04/12/16 19:20, Yann E. MORIN wrote:
[snip]
>>> this comment is shown:
>>>      racehound needs an Linux kernel >= 3.14 to be built
>>
>>   But I would keep this comment if !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14, to
>> make sure the user realizes that he needs a >= 3.14 kernel. He can still
>> select the package if the headers ar < 3.14, so if he knows what he's doing
>> it will be fine.
>
> I respectfully disagree. There is no corelation between the headers and
> the running kernel (except running kernel mnust be more recent than
> headers).

  Exactly: the running kernel must be more recent than the headers. So if the 
headers are too old, there is a chance that the kernel is too old. So I think 
it's useful in that case to present a warning to the user, when he selects the 
package, that he must make sure his kernel is sufficiently recent. That's what 
the dependency I proposed would do.

>
> Besides, this would be misleading in the other way: if headers are 3.14+
> but kernel is 3.13-, the comment wouild not be shown.

  Er, what did you just say about running kernel must be more recent than headers?

>
>>   Even better would be
>> 	depends on !BR2_LINUX_KERNEL || \
>> 		(BR2_PACKAGE_RACEHOUND && !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14)
>> i.e. only show the >= 3.14 warning in case you actually selected racehound.
>
> Again, headers_atl_least_X_Y does not represent the running kernel, so I
> find it a bit misleading that we use that option to show/hide the
> comment.
>
>>> So, this is incorrect, because:
>>>   1- a kernel >= 3.14 is indeed to be built
>>>   2- the headers version mismatch is not reported
>>>
>>> Fix that by moving the dependency on the kernel headers to the
>>> appropriate comment and enhance it.
>>>
>>> Since there is no way we can know the kernel version to be built, we can
>>> not add such a condition; still, we leave the kernel message as-is.
>>
>>   It can be tested in a pre-configure hook. But the cmake rules already check
>> for that, so there's no need to do it again in buildroot.
>
> No, it does not check for it since we pass it -DKERNEL_VERSION_OK=YES

  Why do we do that?

  Regards,
  Arnout


[snip]

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF

[Buildroot] [PATCH] package/racehound: fix comment

[Yann E. MORIN]

Arnout, All,

On 2016-04-13 22:42 +0200, Arnout Vandecappelle spake thusly:
> On 04/13/16 22:18, Yann E. MORIN wrote:
> >Arnout, All,
> >
> >On 2016-04-12 23:27 +0200, Arnout Vandecappelle spake thusly:
> >>On 04/12/16 19:20, Yann E. MORIN wrote:
> [snip]
> >>>this comment is shown:
> >>>     racehound needs an Linux kernel >= 3.14 to be built
> >>
> >>  But I would keep this comment if !BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_14, to
> >>make sure the user realizes that he needs a >= 3.14 kernel. He can still
> >>select the package if the headers ar < 3.14, so if he knows what he's doing
> >>it will be fine.
> >
> >I respectfully disagree. There is no corelation between the headers and
> >the running kernel (except running kernel mnust be more recent than
> >headers).
> 
>  Exactly: the running kernel must be more recent than the headers.

In fact, that's not true (I was wrong). The glibc code will by default
enable workaround for kernels older than the headers, and detect the
version of the kernel it is running on to decide whther to use those
wrokarounds or not.

By default, glibc is *very* conservative, and adds support for kernel
*much* older than the headers (dating back to at least 3.20-or-so IIRC.

This means that, even with headers >= 3.14, a glibc might be able to run
on kernels < 3.14.

In Buildroot, we do configure glibc to not enable those workarounds [0],
utb non-Buildroot toolchains may not do so, like crosstool-Ng which
alows to set an arbitrary value to the oldest supported kernel [1] [2].

So, in fine, we can *not* assume that a toolchain with the appropriate
headers is sufficient to guarantee that the running kernel will be
recent enough.

Note that there were patches (at least a request) floating on the list
that proposed to add such a feature to Buildroot, to be able to specify
the oldest kernel glibc would be able to run under [3].

[0] https://git.buildroot.org/buildroot/tree/package/glibc/glibc.mk#n99
[1] http://crosstool-ng.org/git/crosstool-ng/tree/config/libc/glibc.in.2#n174
[2] http://crosstool-ng.org/git/crosstool-ng/tree/scripts/build/libc/glibc.sh#n501
[3] http://lists.busybox.net/pipermail/buildroot/2016-January/150676.html
and http://lists.busybox.net/pipermail/buildroot/2016-February/thread.html#151640

> So if the
> headers are too old, there is a chance that the kernel is too old. So I
> think it's useful in that case to present a warning to the user, when he
> selects the package, that he must make sure his kernel is sufficiently
> recent. That's what the dependency I proposed would do.

And I don't think that:
 1- it is even correct to begin with, see above;
 2- we should even use the headers_at_least_XXX for that.

> >Besides, this would be misleading in the other way: if headers are 3.14+
> >but kernel is 3.13-, the comment wouild not be shown.
> 
>  Er, what did you just say about running kernel must be more recent than headers?

E.g. the user has a toolchain with 3.14+ headers, but selects a 3.13-
kernel. TRhere is nothing that prevents that in our Kconfig. Not that we
should do it, as it is perfectly possible to run such a kernel, as
explained above (but not with a Buildroot toolchain, however).

> >>>Since there is no way we can know the kernel version to be built, we can
> >>>not add such a condition; still, we leave the kernel message as-is.
> >>  It can be tested in a pre-configure hook. But the cmake rules already check
> >>for that, so there's no need to do it again in buildroot.
> >No, it does not check for it since we pass it -DKERNEL_VERSION_OK=YES
>  Why do we do that?

I guess because otherwise the CMakefile does a test on the host kernel?
It uses ${CMAKE_SYSTEM_VERSION} which is set by CMake to `uname -r`.

Regards,
Yann E. MORIN.

-- 
.-----------------.--------------------.------------------.--------------------.
|  Yann E. MORIN  | Real-Time Embedded | /"\ ASCII RIBBON | Erics' conspiracy: |
| +33 662 376 056 | Software  Designer | \ / CAMPAIGN     |  ___               |
| +33 223 225 172 `------------.-------:  X  AGAINST      |  \e/  There is no  |
| http://ymorin.is-a-geek.org/ | _/*\_ | / \ HTML MAIL    |   v   conspiracy.  |
'------------------------------^-------^------------------^--------------------'