[PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Khem Raj]

This helps it compile with clang or any other compilers besides gcc

Signed-off-by: Khem Raj <raj.khem@gmail.com>
---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 1e4b7d1..2c2d396 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 VERSION = 0.96
-CC=$(CROSS_COMPILE)gcc
-AR=$(CROSS_COMPILE)ar
+CC?=$(CROSS_COMPILE)gcc
+AR?=$(CROSS_COMPILE)ar
 
 OBJDIR = bld
 
-- 
2.6.4

Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Jeff Epler]

I believe the patch does not have the desired effect, because make(1)
always sets CC automatically:

$ cat raj.mk
CROSS_COMPILE=x86_64-linux-gnu-
CC?=$(CROSS_COMPILE)gcc
.PHONY: default
default:
	@echo CC=$(CC)
$ make -f raj.mk
CC=cc

With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
are different, will get different (worse) behavior.

I believe this idea has been discussed before, but it is hard to search
for because few search engines will let you search on "CC ?=" and not
just ignore the "?=".

Also I am not sure why you are submitting this patch on -rt-users, it
doesn't seem to be particularly relevant to the RT patchset.

Jeff

Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Clark Williams]

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On Mon, 4 Jan 2016 07:39:04 -0600
Jeff Epler <jepler@unpythonic.net> wrote:
> 
> Also I am not sure why you are submitting this patch on -rt-users, it
> doesn't seem to be particularly relevant to the RT patchset.
> 
> Jeff

linux-rt-users also is for discussion of RT related user-space code, such as the rt-tests collection.

Clark

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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Khem Raj]

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> On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
> 
> I believe the patch does not have the desired effect, because make(1)
> always sets CC automatically:
> 
> $ cat raj.mk
> CROSS_COMPILE=x86_64-linux-gnu-
> CC?=$(CROSS_COMPILE)gcc
> .PHONY: default
> default:
> 	@echo CC=$(CC)
> $ make -f raj.mk
> CC=cc
> 
> With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
> are different, will get different (worse) behavior.

Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
in Makefile then my issue would be fixed too. However this would mean that cross compiling users
now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
acceptable ?

> 
> I believe this idea has been discussed before, but it is hard to search
> for because few search engines will let you search on "CC ?=" and not
> just ignore the "?=".
> 
> Also I am not sure why you are submitting this patch on -rt-users, it
> doesn't seem to be particularly relevant to the RT patchset.

See the MAINTAINERS file, I just followed whats in there.

> 
> Jeff


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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Uwe Kleine-König]

On Mon, Jan 04, 2016 at 08:20:01AM -0800, Khem Raj wrote:
> 
> > On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
> > 
> > I believe the patch does not have the desired effect, because make(1)
> > always sets CC automatically:
> > 
> > $ cat raj.mk
> > CROSS_COMPILE=x86_64-linux-gnu-
> > CC?=$(CROSS_COMPILE)gcc
> > .PHONY: default
> > default:
> > 	@echo CC=$(CC)
> > $ make -f raj.mk
> > CC=cc
> > 
> > With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
> > are different, will get different (worse) behavior.
> 
> Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
> in Makefile then my issue would be fixed too. However this would mean that cross compiling users
> now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
> acceptable ?

You could play with something like:

ifeq($(origin CC),default)
CC=$(CROSS_COMPILE)gcc
endif

but not sure I'd like the result. If you asked me, I'd drop all that
CROSS_COMPILE stuff.

Best regards
Uwe

-- 
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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Arnout Vandecappelle]

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On 04-01-16 17:20, Khem Raj wrote:
>> On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
>> > 
>> > I believe the patch does not have the desired effect, because make(1)
>> > always sets CC automatically:
>> > 
>> > $ cat raj.mk
>> > CROSS_COMPILE=x86_64-linux-gnu-
>> > CC?=$(CROSS_COMPILE)gcc
>> > .PHONY: default
>> > default:
>> > 	@echo CC=$(CC)
>> > $ make -f raj.mk
>> > CC=cc
>> > 
>> > With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
>> > are different, will get different (worse) behavior.
> Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
> in Makefile then my issue would be fixed too. However this would mean that cross compiling users
> now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
> acceptable ?

 But what is really your issue? Even after this patch, you'll have to run

make CC=<path-to-clang> AR=<path-to-clang-ar>

and this will already override it in the current situation.


 Regards,
 Arnout


-- 
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Senior Embedded Software Architect . . . . . . +32-478-010353 (mobile)
Essensium, Mind division . . . . . . . . . . . . . . http://www.mind.be
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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Khem Raj]

On Mon, Jan 4, 2016 at 11:21 AM, Arnout Vandecappelle
<arnout.vandecappelle@essensium.com> wrote:
> On 04-01-16 17:20, Khem Raj wrote:
>>> On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
>>> >
>>> > I believe the patch does not have the desired effect, because make(1)
>>> > always sets CC automatically:
>>> >
>>> > $ cat raj.mk
>>> > CROSS_COMPILE=x86_64-linux-gnu-
>>> > CC?=$(CROSS_COMPILE)gcc
>>> > .PHONY: default
>>> > default:
>>> >    @echo CC=$(CC)
>>> > $ make -f raj.mk
>>> > CC=cc
>>> >
>>> > With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
>>> > are different, will get different (worse) behavior.
>> Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
>> in Makefile then my issue would be fixed too. However this would mean that cross compiling users
>> now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
>> acceptable ?
>
>  But what is really your issue? Even after this patch, you'll have to run
>
> make CC=<path-to-clang> AR=<path-to-clang-ar>
>
> and this will already override it in the current situation.

currently it ignores CC from environment. So there is no way to
specify a compiler which is not called {something}gcc

>

Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Jeff Epler]

On Mon, Jan 04, 2016 at 08:40:16AM -0600, Clark Williams wrote:
> linux-rt-users also is for discussion of RT related user-space code, such as the rt-tests collection.
> 
> Clark

I apologize.  I didn't read the original patch closely enough and 
incorrectly believed it was a proposed patch for the top-level Makefile
in the linux kernel source tree.

Jeff

Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Henrik Austad]

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On Mon, Jan 04, 2016 at 05:25:07PM +0100, Uwe Kleine-König wrote:
> On Mon, Jan 04, 2016 at 08:20:01AM -0800, Khem Raj wrote:
> > 
> > > On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
> > > 
> > > I believe the patch does not have the desired effect, because make(1)
> > > always sets CC automatically:
> > > 
> > > $ cat raj.mk
> > > CROSS_COMPILE=x86_64-linux-gnu-
> > > CC?=$(CROSS_COMPILE)gcc
> > > .PHONY: default
> > > default:
> > > 	@echo CC=$(CC)
> > > $ make -f raj.mk
> > > CC=cc
> > > 
> > > With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
> > > are different, will get different (worse) behavior.
> > 
> > Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
> > in Makefile then my issue would be fixed too. However this would mean that cross compiling users
> > now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
> > acceptable ?
> 
> You could play with something like:
> 
> ifeq($(origin CC),default)
> CC=$(CROSS_COMPILE)gcc
> endif
> 
> but not sure I'd like the result. If you asked me, I'd drop all that
> CROSS_COMPILE stuff.

Why? Isn't this the normal way of triggering cross-compile? AFIAK, that's 
how the kernel does it, and that seems like a pretty sane way.

And yes, I compile rt-tests to several architectures, so I'm quite fond of 
the CROSS_COMPILE switch. In fact, I might get cross if you cross it out :)

-- 
Henrik Austad

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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Khem Raj]

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> On Jan 5, 2016, at 1:15 PM, Henrik Austad <henrik@austad.us> wrote:
> 
> On Mon, Jan 04, 2016 at 05:25:07PM +0100, Uwe Kleine-König wrote:
>> On Mon, Jan 04, 2016 at 08:20:01AM -0800, Khem Raj wrote:
>>> 
>>>> On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
>>>> 
>>>> I believe the patch does not have the desired effect, because make(1)
>>>> always sets CC automatically:
>>>> 
>>>> $ cat raj.mk
>>>> CROSS_COMPILE=x86_64-linux-gnu-
>>>> CC?=$(CROSS_COMPILE)gcc
>>>> .PHONY: default
>>>> default:
>>>> 	@echo CC=$(CC)
>>>> $ make -f raj.mk
>>>> CC=cc
>>>> 
>>>> With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
>>>> are different, will get different (worse) behavior.
>>> 
>>> Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
>>> in Makefile then my issue would be fixed too. However this would mean that cross compiling users
>>> now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
>>> acceptable ?
>> 
>> You could play with something like:
>> 
>> ifeq($(origin CC),default)
>> CC=$(CROSS_COMPILE)gcc
>> endif
>> 
>> but not sure I'd like the result. If you asked me, I'd drop all that
>> CROSS_COMPILE stuff.
> 
> Why? Isn't this the normal way of triggering cross-compile? AFIAK, that's
> how the kernel does it, and that seems like a pretty sane way.

except, kernel lets you override CC if you want to.

> 
> And yes, I compile rt-tests to several architectures, so I'm quite fond of
> the CROSS_COMPILE switch. In fact, I might get cross if you cross it out :)

All you would need is to add

CC = ${CROSS_COMPILE}gcc in one place in your Make env

> 
> --
> Henrik Austad


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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[Uwe Kleine-König]

Hello Henrik,

On Tue, Jan 05, 2016 at 10:15:56PM +0100, Henrik Austad wrote:
> On Mon, Jan 04, 2016 at 05:25:07PM +0100, Uwe Kleine-König wrote:
> > On Mon, Jan 04, 2016 at 08:20:01AM -0800, Khem Raj wrote:
> > > 
> > > > On Jan 4, 2016, at 5:39 AM, Jeff Epler <jepler@unpythonic.net> wrote:
> > > > 
> > > > I believe the patch does not have the desired effect, because make(1)
> > > > always sets CC automatically:
> > > > 
> > > > $ cat raj.mk
> > > > CROSS_COMPILE=x86_64-linux-gnu-
> > > > CC?=$(CROSS_COMPILE)gcc
> > > > .PHONY: default
> > > > default:
> > > > 	@echo CC=$(CC)
> > > > $ make -f raj.mk
> > > > CC=cc
> > > > 
> > > > With your patch, those who specify CROSS_COMPILE, or for whom gcc and cc
> > > > are different, will get different (worse) behavior.
> > > 
> > > Right. I think if CC was used as such with out constructing out of CROSS_COMPILE
> > > in Makefile then my issue would be fixed too. However this would mean that cross compiling users
> > > now have to pass CC = <cross-compiler> themselves instead of CROSS_COMPILE prefix. Is that
> > > acceptable ?
> > 
> > You could play with something like:
> > 
> > ifeq($(origin CC),default)
> > CC=$(CROSS_COMPILE)gcc
> > endif
> > 
> > but not sure I'd like the result. If you asked me, I'd drop all that
> > CROSS_COMPILE stuff.
> 
> Why? Isn't this the normal way of triggering cross-compile? AFIAK, that's 
> how the kernel does it, and that seems like a pretty sane way.

No, the normal thing to trigger a cross-compile is

	./configure --build=amd64 --host=mips-elf

:-)

For plain make project with no special support for cross compiling
(which is the norm today), the right incarnation is:

	make CC=arm-v5te-linux-gnueabi-gcc

and IMHO that's good enough. (Sometimes you also have to pass CXX, in
rare cases even more.)

> And yes, I compile rt-tests to several architectures, so I'm quite fond of 
> the CROSS_COMPILE switch. In fact, I might get cross if you cross it out :)

I don't care much, because if I cross compile rt-tests someone else
already found out for me how to do it, I only have to enable it in my
config :-)

Best regards
Uwe

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Re: [PATCH] Makefile: Set CC/AR variable only if it doesn't have a value

[John Kacur]

On Sun, 3 Jan 2016, Khem Raj wrote:

> This helps it compile with clang or any other compilers besides gcc
> 
> Signed-off-by: Khem Raj <raj.khem@gmail.com>
> ---
>  Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 1e4b7d1..2c2d396 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1,6 +1,6 @@
>  VERSION = 0.96
> -CC=$(CROSS_COMPILE)gcc
> -AR=$(CROSS_COMPILE)ar
> +CC?=$(CROSS_COMPILE)gcc
> +AR?=$(CROSS_COMPILE)ar
>  
>  OBJDIR = bld
>  
> -- 

Signed-off-by: John Kacur <jkacur@gmail.com>

I added this to the next build.

Note, I read everything in the thread, and I think there was a bit of 
confusion over thinking this was a kernel Makefile and not
the rt-tests one. As clark said, this is indeed the appropriate place to
discuss user space tools that are to do with real-time.
Perhaps after [PATCH] add rt-tests: to make it clear.

This patch is fine, it changes nothing other than letting the Khem and 
others specify CC and AR from the command line when typing make.

Thanks