kernel/bounds.c is recompiled on every build, and shows the following
warning when compiling with W=1:
CC kernel/bounds.s
linux/kernel/bounds.c:16:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
void foo(void)
^~~
Provide a prototype to satisfy the compiler.
Signed-off-by: Kieran Bingham <[email protected]>
Cc: [email protected]
---
I compile all of my incremental builds with W=1, which allows me to know
instantly if I add a new compiler warning in code I generate.
This warning always comes up and seems trivial to clean up.
---
kernel/bounds.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/kernel/bounds.c b/kernel/bounds.c
index c373e887c066..60136d937800 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -13,6 +13,8 @@
#include <linux/log2.h>
#include <linux/spinlock_types.h>
+void foo(void);
+
void foo(void)
{
/* The enum constants to put into include/generated/bounds.h */
--
2.17.1
On Fri, Sep 21, 2018 at 03:22:33PM +0100, Kieran Bingham wrote:
> kernel/bounds.c is recompiled on every build, and shows the following
> warning when compiling with W=1:
Don't do that, you will get a lot of warnings that really don't make
much sense. Like this one :)
>
> CC kernel/bounds.s
> linux/kernel/bounds.c:16:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
> void foo(void)
> ^~~
>
> Provide a prototype to satisfy the compiler.
>
> Signed-off-by: Kieran Bingham <[email protected]>
> Cc: [email protected]
>
> ---
> I compile all of my incremental builds with W=1, which allows me to know
> instantly if I add a new compiler warning in code I generate.
>
> This warning always comes up and seems trivial to clean up.
> ---
> kernel/bounds.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index c373e887c066..60136d937800 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -13,6 +13,8 @@
> #include <linux/log2.h>
> #include <linux/spinlock_types.h>
>
> +void foo(void);
> +
> void foo(void)
This file is a userspace tool that is used to later generate the
include/generated/bounds.h file.
If you really want to track this down and fix it properly, put the
prototype in the .c file that ends up calling this function. That's a
fun task to dig through the build system to find :)
good luck!
greg k-h
Hi Greg,
Thank you for quick response!
On 21/09/18 15:45, Greg Kroah-Hartman wrote:
> On Fri, Sep 21, 2018 at 03:22:33PM +0100, Kieran Bingham wrote:
>> kernel/bounds.c is recompiled on every build, and shows the following
>> warning when compiling with W=1:
So it turns out after a bit more checking that my statement above was a
small lie :)
My local build scripts were *causing* kernel/bounds.s to be rebuilt on
every build, which is why this stood out to me - because of two
competing compiles for the kernel image, and the dtb.
One with W=1 and the other without... (kbuild detected different flags,
and thus rebuilt the common objects)
And that's why I saw this warning on every build... and thought this was
a hot-path.
> Don't do that, you will get a lot of warnings that really don't make
> much sense. Like this one :)
I know - but I can ignore all on my first build, then on incremental
builds where only files I change are compiled - it's much quieter :)
I see it as a benefit to compile *my* code with a higher warning level,
to prevent /me/ adding further warnings.
I realise of course this patch is just pandering to the compiler to shut
it up, as this is essentially an 'unused' dummy function from it's
perspective.
But in this instance, it's because the output is being compiled to an
assembly output (kernel/bounds.s) which is then later parsed, so there
isn't anywhere else to define the prototype, and the object code is only
referenced from the assembly output.
>>
>> CC kernel/bounds.s
>> linux/kernel/bounds.c:16:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
>> void foo(void)
>> ^~~
>>
>> Provide a prototype to satisfy the compiler.
>>
>> Signed-off-by: Kieran Bingham <[email protected]>
>> Cc: [email protected]
>>
>> ---
>> I compile all of my incremental builds with W=1, which allows me to know
>> instantly if I add a new compiler warning in code I generate.
>>
>> This warning always comes up and seems trivial to clean up.
>> ---
>> kernel/bounds.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/kernel/bounds.c b/kernel/bounds.c
>> index c373e887c066..60136d937800 100644
>> --- a/kernel/bounds.c
>> +++ b/kernel/bounds.c
>> @@ -13,6 +13,8 @@
>> #include <linux/log2.h>
>> #include <linux/spinlock_types.h>
>>
>> +void foo(void);
>> +
>> void foo(void)
>
> This file is a userspace tool that is used to later generate the
> include/generated/bounds.h file.
Well more accurately it is a file compiled directly to assembly which is
then later parsed to help generate the bounds.h file. It's not itself a
userspace tool, nothing executes this code...
It's just a compilation object to allow utilisation of the preprocessor
and compiler in ways that couldn't be done otherwise as far as I
understand it.
> If you really want to track this down and fix it properly, put the
> prototype in the .c file that ends up calling this function. That's a
> fun task to dig through the build system to find :)
This is the only location.
The compilation output from V=1 (https://paste.debian.net/1043598/ for
the full output) shows the command generating this warning as:
(with many flags redacted for readability)
aarch64-linux-gnu-gcc -Wp,-MD,kernel/.bounds.s.d -nostdinc -Wall
-Wstrict-prototypes -DKBUILD_BASENAME='"bounds"'
-DKBUILD_MODNAME='"bounds"' -fverbose-asm -S -o kernel/bounds.s
kernel/bounds.c
I still feel this patch has 'some' merit with the inaccurate leading
statement regarding this being output on every build removed from the
commit log.
What do you think ?
Worth a v2 with commit message fixed?
Or should I just drop this ?
> good luck!
>
> greg k-h
--
Cheers
Kieran
On 21/09/18 16:58, Kieran Bingham wrote:
> Hi Greg,
>
> Thank you for quick response!
Ahem; s/for quick/for your quick/
I hate re-reading mails after I hit send and spotting things like this.
Sigh :-)
Regards
--
Kieran
Building any configuration with 'make W=1' produces a warning:
kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
When also passing -Werror, this prevents us from building any
other files. Nobody ever calls the function, but we can't make
it 'static' either since we want the compiler output.
Calling it 'main' instead however avoids the warning, because gcc
does not insist on having a declaration for main.
Reported-by: Kieran Bingham <[email protected]>
Cc: [email protected]
Signed-off-by: Arnd Bergmann <[email protected]>
---
I have run into this problem several times before, and thought I had
sent a fix at some point. Looking in the archives, I came across
the suggested fix from Kieran, so I'm following up on that here.
---
kernel/bounds.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/kernel/bounds.c b/kernel/bounds.c
index c373e887c066..9795d75b09b2 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -13,7 +13,7 @@
#include <linux/log2.h>
#include <linux/spinlock_types.h>
-void foo(void)
+int main(void)
{
/* The enum constants to put into include/generated/bounds.h */
DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
@@ -23,4 +23,6 @@ void foo(void)
#endif
DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
/* End of constants */
+
+ return 0;
}
--
2.18.0
Hi Arnd,
On 05/10/18 09:33, Arnd Bergmann wrote:
> Building any configuration with 'make W=1' produces a warning:
>
> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
>
s/warnign/warning/ but I don't think that's too important :D
> When also passing -Werror, this prevents us from building any
> other files. Nobody ever calls the function, but we can't make
> it 'static' either since we want the compiler output.
>
> Calling it 'main' instead however avoids the warning, because gcc
> does not insist on having a declaration for main.
Aha - even better! (and annoyingly fairly obvious, from the
Why-didn't-I-think-of-that department).
> Reported-by: Kieran Bingham <[email protected]>
> Cc: [email protected]
> Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Kieran Bingham <[email protected]>
> ---
> I have run into this problem several times before, and thought I had
> sent a fix at some point. Looking in the archives, I came across
> the suggested fix from Kieran, so I'm following up on that here.
> ---
> kernel/bounds.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index c373e887c066..9795d75b09b2 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -13,7 +13,7 @@
> #include <linux/log2.h>
> #include <linux/spinlock_types.h>
>
> -void foo(void)
> +int main(void)
> {
> /* The enum constants to put into include/generated/bounds.h */
> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
> @@ -23,4 +23,6 @@ void foo(void)
> #endif
> DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
> /* End of constants */
> +
> + return 0;
> }
>
From: Arnd Bergmann
> Sent: 05 October 2018 09:33
>
> Building any configuration with 'make W=1' produces a warning:
>
> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
>
> When also passing -Werror, this prevents us from building any
> other files. Nobody ever calls the function, but we can't make
> it 'static' either since we want the compiler output.
>
> Calling it 'main' instead however avoids the warning, because gcc
> does not insist on having a declaration for main.
Ugg.
main() might be special in other ways too.
It wouldn't surprise me if some linkers don't do special stuff for it.
What is wrong with just putting and extra "void foo(void);" before
the function?
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
On Fri, Oct 5, 2018 at 10:52 AM David Laight <[email protected]> wrote:
>
> From: Arnd Bergmann
> > Sent: 05 October 2018 09:33
> >
> > Building any configuration with 'make W=1' produces a warning:
> >
> > kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
> >
> > When also passing -Werror, this prevents us from building any
> > other files. Nobody ever calls the function, but we can't make
> > it 'static' either since we want the compiler output.
> >
> > Calling it 'main' instead however avoids the warning, because gcc
> > does not insist on having a declaration for main.
>
> Ugg.
> main() might be special in other ways too.
> It wouldn't surprise me if some linkers don't do special stuff for it.
>
> What is wrong with just putting and extra "void foo(void);" before
> the function?
Greg objected to that on the basis that we don't want declarations
in .c files -- they should be in a shared header:
https://lkml.org/lkml/2018/9/21/735
I don't see what could go wrong here with calling it main(), after
all we are just interested in the assembler output, not even
creating an object file.
Arnd
On 05/10/18 10:07, Arnd Bergmann wrote:
> On Fri, Oct 5, 2018 at 10:52 AM David Laight <[email protected]> wrote:
>>
>> From: Arnd Bergmann
>>> Sent: 05 October 2018 09:33
>>>
>>> Building any configuration with 'make W=1' produces a warning:
>>>
>>> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
>>>
>>> When also passing -Werror, this prevents us from building any
>>> other files. Nobody ever calls the function, but we can't make
>>> it 'static' either since we want the compiler output.
>>>
>>> Calling it 'main' instead however avoids the warning, because gcc
>>> does not insist on having a declaration for main.
>>
>> Ugg.
>> main() might be special in other ways too.
>> It wouldn't surprise me if some linkers don't do special stuff for it.
I worried about this but didn't think it would be too much of an issue.
But perhaps we should check...
<compile bounds.s in both configurations> as bounds.s.foo and bounds.s.main:
diff -Nurp bounds.s.*
--- bounds.s.foo 2018-10-05 10:20:53.269941404 +0100
+++ bounds.s.main 2018-10-05 10:20:31.375891260 +0100
@@ -108,11 +108,12 @@
.global _mcount
#NO_APP
+ .section .text.startup,"ax",@progbits
.align 2
.p2align 3,,7
- .global foo
- .type foo, %function
-foo:
+ .global main
+ .type main, %function
+main:
stp x29, x30, [sp, -16]! //,,,
add x29, sp, 0 //,,
// /home/linuxembedded/iob/renesas/vsp1/sources/linux/kernel/bounds.c:17: {
@@ -139,10 +140,11 @@ foo:
.ascii "->SPINLOCK_SIZE 56 sizeof(spinlock_t)" //
// 0 "" 2
-// /home/linuxembedded/iob/renesas/vsp1/sources/linux/kernel/bounds.c:26: }
+// /home/linuxembedded/iob/renesas/vsp1/sources/linux/kernel/bounds.c:28: }
#NO_APP
+ mov w0, 0 //,
ldp x29, x30, [sp], 16 //,,,
ret
- .size foo, .-foo
+ .size main, .-main
.ident "GCC: (Ubuntu/Linaro 7.3.0-16ubuntu3) 7.3.0"
.section .note.GNU-stack,"",@progbits
compiled with aarch64-linux-gnu-gcc, and with no debug enabled.
Other than the entry point rename (and section name) and the return
value being added, I can't see anything problematic here.
And as far as I know - this file gets processed after to extract
definitions which should be independent. This file is not executed or
further compiled as far as I am aware.
--
Kieran
>>
>> What is wrong with just putting and extra "void foo(void);" before
>> the function?
>
> Greg objected to that on the basis that we don't want declarations
> in .c files -- they should be in a shared header:
>
> https://lkml.org/lkml/2018/9/21/735
>
> I don't see what could go wrong here with calling it main(), after
> all we are just interested in the assembler output, not even
> creating an object file.
>
> Arnd
>
On Fri, Oct 5, 2018 at 5:34 PM Arnd Bergmann <[email protected]> wrote:
>
> Building any configuration with 'make W=1' produces a warning:
>
> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
>
> When also passing -Werror, this prevents us from building any
> other files. Nobody ever calls the function, but we can't make
> it 'static' either since we want the compiler output.
>
> Calling it 'main' instead however avoids the warning, because gcc
> does not insist on having a declaration for main.
>
> Reported-by: Kieran Bingham <[email protected]>
> Cc: [email protected]
> Signed-off-by: Arnd Bergmann <[email protected]>
> ---
Applied to kbuild/fixes
with 's/warnign/warning/'
Thanks!
> I have run into this problem several times before, and thought I had
> sent a fix at some point. Looking in the archives, I came across
> the suggested fix from Kieran, so I'm following up on that here.
> ---
> kernel/bounds.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index c373e887c066..9795d75b09b2 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -13,7 +13,7 @@
> #include <linux/log2.h>
> #include <linux/spinlock_types.h>
>
> -void foo(void)
> +int main(void)
> {
> /* The enum constants to put into include/generated/bounds.h */
> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
> @@ -23,4 +23,6 @@ void foo(void)
> #endif
> DEFINE(SPINLOCK_SIZE, sizeof(spinlock_t));
> /* End of constants */
> +
> + return 0;
> }
> --
> 2.18.0
>
--
Best Regards
Masahiro Yamada
On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann <[email protected]> wrote:
>
> Building any configuration with 'make W=1' produces a warning:
>
> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
>
> When also passing -Werror, this prevents us from building any
> other files. Nobody ever calls the function, but we can't make
> it 'static' either since we want the compiler output.
>
> Calling it 'main' instead however avoids the warning, because gcc
> does not insist on having a declaration for main.
I think marking the function as static __used should do the trick and
would be less confusing.
Cheers,
Miguel
Hi Miguel,
On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda
<[email protected]> wrote:
>
> On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann <[email protected]> wrote:
> >
> > Building any configuration with 'make W=1' produces a warning:
> >
> > kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
> >
> > When also passing -Werror, this prevents us from building any
> > other files. Nobody ever calls the function, but we can't make
> > it 'static' either since we want the compiler output.
> >
> > Calling it 'main' instead however avoids the warning, because gcc
> > does not insist on having a declaration for main.
>
> I think marking the function as static __used should do the trick and
> would be less confusing.
I tried __used, but I still see the warning.
masahiro@grover:~/ref/linux$ git diff
diff --git a/kernel/bounds.c b/kernel/bounds.c
index c373e88..aee0101 100644
--- a/kernel/bounds.c
+++ b/kernel/bounds.c
@@ -13,7 +13,7 @@
#include <linux/log2.h>
#include <linux/spinlock_types.h>
-void foo(void)
+void __used foo(void)
{
/* The enum constants to put into include/generated/bounds.h */
DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
masahiro@grover:~/ref/linux$ make W=1 prepare
CC kernel/bounds.s
kernel/bounds.c:16:13: warning: no previous prototype for ‘foo’
[-Wmissing-prototypes]
void __used foo(void)
^
CC arch/x86/kernel/asm-offsets.s
--
Best Regards
Masahiro Yamada
On Sun, Oct 7, 2018 at 6:58 AM Masahiro Yamada
<[email protected]> wrote:
>
> Hi Miguel,
>
>
> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda
> <[email protected]> wrote:
> >
> > On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann <[email protected]> wrote:
> > >
> > > Building any configuration with 'make W=1' produces a warning:
> > >
> > > kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
> > >
> > > When also passing -Werror, this prevents us from building any
> > > other files. Nobody ever calls the function, but we can't make
> > > it 'static' either since we want the compiler output.
> > >
> > > Calling it 'main' instead however avoids the warning, because gcc
> > > does not insist on having a declaration for main.
> >
> > I think marking the function as static __used should do the trick and
> > would be less confusing.
>
>
>
>
> I tried __used, but I still see the warning.
>
>
> masahiro@grover:~/ref/linux$ git diff
> diff --git a/kernel/bounds.c b/kernel/bounds.c
> index c373e88..aee0101 100644
> --- a/kernel/bounds.c
> +++ b/kernel/bounds.c
> @@ -13,7 +13,7 @@
> #include <linux/log2.h>
> #include <linux/spinlock_types.h>
>
> -void foo(void)
> +void __used foo(void)
> {
> /* The enum constants to put into include/generated/bounds.h */
> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
> masahiro@grover:~/ref/linux$ make W=1 prepare
> CC kernel/bounds.s
> kernel/bounds.c:16:13: warning: no previous prototype for ‘foo’
> [-Wmissing-prototypes]
> void __used foo(void)
> ^
> CC arch/x86/kernel/asm-offsets.s
Sorry, I forgot to add 'static'.
Adding both static and __used worked for me,
and I like the idea.
--
Best Regards
Masahiro Yamada
Hi Masahiro,
On Sat, Oct 6, 2018 at 11:59 PM Masahiro Yamada
<[email protected]> wrote:
>
> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda
> <[email protected]> wrote:
> >
> > I think marking the function as static __used should do the trick and
> > would be less confusing.
>
> I tried __used, but I still see the warning.
It has to be static __used, not only __used! :-)
Cheers,
Miguel
On 06/10/18 23:06, Masahiro Yamada wrote:
> On Sun, Oct 7, 2018 at 6:58 AM Masahiro Yamada
> <[email protected]> wrote:
>>
>> Hi Miguel,
>>
>>
>> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda
>> <[email protected]> wrote:
>>>
>>> On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann <[email protected]> wrote:
>>>>
>>>> Building any configuration with 'make W=1' produces a warning:
>>>>
>>>> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
>>>>
>>>> When also passing -Werror, this prevents us from building any
>>>> other files. Nobody ever calls the function, but we can't make
>>>> it 'static' either since we want the compiler output.
>>>>
>>>> Calling it 'main' instead however avoids the warning, because gcc
>>>> does not insist on having a declaration for main.
>>>
>>> I think marking the function as static __used should do the trick and
>>> would be less confusing.
>>
>>
>>
>>
>> I tried __used, but I still see the warning.
>>
>>
>> masahiro@grover:~/ref/linux$ git diff
>> diff --git a/kernel/bounds.c b/kernel/bounds.c
>> index c373e88..aee0101 100644
>> --- a/kernel/bounds.c
>> +++ b/kernel/bounds.c
>> @@ -13,7 +13,7 @@
>> #include <linux/log2.h>
>> #include <linux/spinlock_types.h>
>>
>> -void foo(void)
>> +void __used foo(void)
>> {
>> /* The enum constants to put into include/generated/bounds.h */
>> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
>> masahiro@grover:~/ref/linux$ make W=1 prepare
>> CC kernel/bounds.s
>> kernel/bounds.c:16:13: warning: no previous prototype for ‘foo’
>> [-Wmissing-prototypes]
>> void __used foo(void)
>> ^
>> CC arch/x86/kernel/asm-offsets.s
>
>
>
> Sorry, I forgot to add 'static'.
>
> Adding both static and __used worked for me,
> and I like the idea.
>
Aha - I'd also tried converting to static in my earlier attempts, but
didn't realise we had __used!
updating as "static __used" causes the following diff:
diff -Nurp bounds.s.foo bounds.s.static-used
--- bounds.s.foo 2018-10-05 10:20:53.269941404 +0100
+++ bounds.s.static-used 2018-10-08 10:51:18.079309049 +0100
@@ -110,7 +110,6 @@
#NO_APP
.align 2
.p2align 3,,7
- .global foo
.type foo, %function
foo:
stp x29, x30, [sp, -16]! //,,,
I'd say this is a pretty good alternative fix - however I see Arnd's
version is already on it's way though akpm's tree...
https://ozlabs.org/~akpm/mmots/broken-out/kbuild-fix-kernel-boundsc-w%3D1-warning.patch
Anyway, as long as one of the variants gets there I'll be happy :)
--
Regards
Kieran
On Mon, Oct 8, 2018 at 7:01 PM Kieran Bingham
<[email protected]> wrote:
>
> On 06/10/18 23:06, Masahiro Yamada wrote:
> > On Sun, Oct 7, 2018 at 6:58 AM Masahiro Yamada
> > <[email protected]> wrote:
> >>
> >> Hi Miguel,
> >>
> >>
> >> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda
> >> <[email protected]> wrote:
> >>>
> >>> On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann <[email protected]> wrote:
> >>>>
> >>>> Building any configuration with 'make W=1' produces a warning:
> >>>>
> >>>> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
> >>>>
> >>>> When also passing -Werror, this prevents us from building any
> >>>> other files. Nobody ever calls the function, but we can't make
> >>>> it 'static' either since we want the compiler output.
> >>>>
> >>>> Calling it 'main' instead however avoids the warning, because gcc
> >>>> does not insist on having a declaration for main.
> >>>
> >>> I think marking the function as static __used should do the trick and
> >>> would be less confusing.
> >>
> >>
> >>
> >>
> >> I tried __used, but I still see the warning.
> >>
> >>
> >> masahiro@grover:~/ref/linux$ git diff
> >> diff --git a/kernel/bounds.c b/kernel/bounds.c
> >> index c373e88..aee0101 100644
> >> --- a/kernel/bounds.c
> >> +++ b/kernel/bounds.c
> >> @@ -13,7 +13,7 @@
> >> #include <linux/log2.h>
> >> #include <linux/spinlock_types.h>
> >>
> >> -void foo(void)
> >> +void __used foo(void)
> >> {
> >> /* The enum constants to put into include/generated/bounds.h */
> >> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
> >> masahiro@grover:~/ref/linux$ make W=1 prepare
> >> CC kernel/bounds.s
> >> kernel/bounds.c:16:13: warning: no previous prototype for ‘foo’
> >> [-Wmissing-prototypes]
> >> void __used foo(void)
> >> ^
> >> CC arch/x86/kernel/asm-offsets.s
> >
> >
> >
> > Sorry, I forgot to add 'static'.
> >
> > Adding both static and __used worked for me,
> > and I like the idea.
> >
>
> Aha - I'd also tried converting to static in my earlier attempts, but
> didn't realise we had __used!
>
> updating as "static __used" causes the following diff:
>
> diff -Nurp bounds.s.foo bounds.s.static-used
> --- bounds.s.foo 2018-10-05 10:20:53.269941404 +0100
> +++ bounds.s.static-used 2018-10-08 10:51:18.079309049 +0100
> @@ -110,7 +110,6 @@
> #NO_APP
> .align 2
> .p2align 3,,7
> - .global foo
> .type foo, %function
> foo:
> stp x29, x30, [sp, -16]! //,,,
>
>
> I'd say this is a pretty good alternative fix - however I see Arnd's
> version is already on it's way though akpm's tree...
>
> https://ozlabs.org/~akpm/mmots/broken-out/kbuild-fix-kernel-boundsc-w%3D1-warning.patch
>
> Anyway, as long as one of the variants gets there I'll be happy :)
I will leave it to Arnd.
When we fix arch/{mips,sparc}/kernel/asm-offsets.c,
'static __used' is just additions.
The 'main(void)' solution would require a little bit restructuring.
FWIW, with my quick analysis, the following should be fixed as well:
arch/alpha/kernel/asm-offsets.c
arch/c6x/kernel/asm-offsets.c
arch/ia64/kernel/asm-offsets.c
arch/ia64/kernel/nr-irqs.c
arch/mips/kernel/asm-offsets.c
arch/riscv/kernel/asm-offsets.c
arch/sparc/kernel/asm-offsets.c
arch/x86/kernel/asm-offsets.c
arch/x86/um/shared/sysdep/kernel-offsets.h
samples/bpf/syscall_nrs.c
--
Best Regards
Masahiro Yamada
On Mon, Oct 8, 2018 at 4:33 PM Masahiro Yamada
<[email protected]> wrote:
> On Mon, Oct 8, 2018 at 7:01 PM Kieran Bingham
> <[email protected]> wrote:
> > On 06/10/18 23:06, Masahiro Yamada wrote:
> > > On Sun, Oct 7, 2018 at 6:58 AM Masahiro Yamada
> > > <[email protected]> wrote:
> > >>
> > >> Hi Miguel,
> > >>
> > >>
> > >> On Sun, Oct 7, 2018 at 6:18 AM Miguel Ojeda
> > >> <[email protected]> wrote:
> > >>>
> > >>> On Fri, Oct 5, 2018 at 10:35 AM Arnd Bergmann <[email protected]> wrote:
> > >>>>
> > >>>> Building any configuration with 'make W=1' produces a warning:
> > >>>>
> > >>>> kernel/bounds.c:16:6: warnign: no previous prototype for 'foo' [-Wmissing-prototypes]
> > >>>>
> > >>>> When also passing -Werror, this prevents us from building any
> > >>>> other files. Nobody ever calls the function, but we can't make
> > >>>> it 'static' either since we want the compiler output.
> > >>>>
> > >>>> Calling it 'main' instead however avoids the warning, because gcc
> > >>>> does not insist on having a declaration for main.
> > >>>
> > >>> I think marking the function as static __used should do the trick and
> > >>> would be less confusing.
> > >>
> > >>
> > >>
> > >>
> > >> I tried __used, but I still see the warning.
> > >>
> > >>
> > >> masahiro@grover:~/ref/linux$ git diff
> > >> diff --git a/kernel/bounds.c b/kernel/bounds.c
> > >> index c373e88..aee0101 100644
> > >> --- a/kernel/bounds.c
> > >> +++ b/kernel/bounds.c
> > >> @@ -13,7 +13,7 @@
> > >> #include <linux/log2.h>
> > >> #include <linux/spinlock_types.h>
> > >>
> > >> -void foo(void)
> > >> +void __used foo(void)
> > >> {
> > >> /* The enum constants to put into include/generated/bounds.h */
> > >> DEFINE(NR_PAGEFLAGS, __NR_PAGEFLAGS);
> > >> masahiro@grover:~/ref/linux$ make W=1 prepare
> > >> CC kernel/bounds.s
> > >> kernel/bounds.c:16:13: warning: no previous prototype for ‘foo’
> > >> [-Wmissing-prototypes]
> > >> void __used foo(void)
> > >> ^
> > >> CC arch/x86/kernel/asm-offsets.s
> > >
> > >
> > >
> > > Sorry, I forgot to add 'static'.
> > >
> > > Adding both static and __used worked for me,
> > > and I like the idea.
> > >
> >
> > Aha - I'd also tried converting to static in my earlier attempts, but
> > didn't realise we had __used!
> >
> > updating as "static __used" causes the following diff:
> >
> > diff -Nurp bounds.s.foo bounds.s.static-used
> > --- bounds.s.foo 2018-10-05 10:20:53.269941404 +0100
> > +++ bounds.s.static-used 2018-10-08 10:51:18.079309049 +0100
> > @@ -110,7 +110,6 @@
> > #NO_APP
> > .align 2
> > .p2align 3,,7
> > - .global foo
> > .type foo, %function
> > foo:
> > stp x29, x30, [sp, -16]! //,,,
> >
> >
> > I'd say this is a pretty good alternative fix - however I see Arnd's
> > version is already on it's way though akpm's tree...
> >
> > https://ozlabs.org/~akpm/mmots/broken-out/kbuild-fix-kernel-boundsc-w%3D1-warning.patch
> >
> > Anyway, as long as one of the variants gets there I'll be happy :)
>
>
> I will leave it to Arnd.
>
>
> When we fix arch/{mips,sparc}/kernel/asm-offsets.c,
> 'static __used' is just additions.
>
> The 'main(void)' solution would require a little bit restructuring.
>
>
>
> FWIW, with my quick analysis, the following should be fixed as well:
>
> arch/alpha/kernel/asm-offsets.c
> arch/c6x/kernel/asm-offsets.c
> arch/ia64/kernel/asm-offsets.c
> arch/ia64/kernel/nr-irqs.c
> arch/mips/kernel/asm-offsets.c
> arch/riscv/kernel/asm-offsets.c
> arch/sparc/kernel/asm-offsets.c
> arch/x86/kernel/asm-offsets.c
> arch/x86/um/shared/sysdep/kernel-offsets.h
> samples/bpf/syscall_nrs.c
All the other asm-offsets.c files already use "int main(void)" ;-)
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds