2021-03-16 23:00:16

by Victor Erminpour

Subject: [PATCH] btrfs: Use immediate assignment when referencing cc-option

Calling cc-option will use KBUILD_CFLAGS, which when lazy setting
subdir-ccflags-y produces the following build error:

scripts/Makefile.lib:10: *** Recursive variable `KBUILD_CFLAGS' \
references itself (eventually). Stop.

Use := assignment to subdir-ccflags-y when referencing cc-option.
This causes make to also evaluate += immediately, cc-option
calls are done right away and we don't end up with KBUILD_CFLAGS
referencing itself.

Signed-off-by: Victor Erminpour <[email protected]>
---
fs/btrfs/Makefile | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
index b634c42115ea..3dba1336fa95 100644
--- a/fs/btrfs/Makefile
+++ b/fs/btrfs/Makefile
@@ -7,10 +7,10 @@ subdir-ccflags-y += -Wmissing-format-attribute
subdir-ccflags-y += -Wmissing-prototypes
subdir-ccflags-y += -Wold-style-definition
subdir-ccflags-y += -Wmissing-include-dirs
-subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
-subdir-ccflags-y += $(call cc-option, -Wunused-const-variable)
-subdir-ccflags-y += $(call cc-option, -Wpacked-not-aligned)
-subdir-ccflags-y += $(call cc-option, -Wstringop-truncation)
+subdir-ccflags-y := $(call cc-option, -Wunused-but-set-variable)
+subdir-ccflags-y := $(call cc-option, -Wunused-const-variable)
+subdir-ccflags-y := $(call cc-option, -Wpacked-not-aligned)
+subdir-ccflags-y := $(call cc-option, -Wstringop-truncation)
# The following turn off the warnings enabled by -Wextra
subdir-ccflags-y += -Wno-missing-field-initializers
subdir-ccflags-y += -Wno-sign-compare

2021-03-17 02:32:23

by Anand Jain

Subject: Re: [PATCH] btrfs: Use immediate assignment when referencing cc-option

On 17/03/2021 06:46, Victor Erminpour wrote:
> Calling cc-option will use KBUILD_CFLAGS, which when lazy setting
> subdir-ccflags-y produces the following build error:
>
> scripts/Makefile.lib:10: *** Recursive variable `KBUILD_CFLAGS' \
> references itself (eventually). Stop.
>
> Use := assignment to subdir-ccflags-y when referencing cc-option.
> This causes make to also evaluate += immediately, cc-option
> calls are done right away and we don't end up with KBUILD_CFLAGS
> referencing itself.
>

Thanks for the patch.
Reviewed-by: Anand Jain <[email protected]>

> Signed-off-by: Victor Erminpour <[email protected]>
> ---
> fs/btrfs/Makefile | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
> index b634c42115ea..3dba1336fa95 100644
> --- a/fs/btrfs/Makefile
> +++ b/fs/btrfs/Makefile
> @@ -7,10 +7,10 @@ subdir-ccflags-y += -Wmissing-format-attribute
> subdir-ccflags-y += -Wmissing-prototypes
> subdir-ccflags-y += -Wold-style-definition
> subdir-ccflags-y += -Wmissing-include-dirs
> -subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
> -subdir-ccflags-y += $(call cc-option, -Wunused-const-variable)
> -subdir-ccflags-y += $(call cc-option, -Wpacked-not-aligned)
> -subdir-ccflags-y += $(call cc-option, -Wstringop-truncation)


> +subdir-ccflags-y := $(call cc-option, -Wunused-but-set-variable)
> +subdir-ccflags-y := $(call cc-option, -Wunused-const-variable)
> +subdir-ccflags-y := $(call cc-option, -Wpacked-not-aligned)
> +subdir-ccflags-y := $(call cc-option, -Wstringop-truncation)




> # The following turn off the warnings enabled by -Wextra
> subdir-ccflags-y += -Wno-missing-field-initializers
> subdir-ccflags-y += -Wno-sign-compare
>

2021-03-17 06:42:31

by Nikolay Borisov

Subject: Re: [PATCH] btrfs: Use immediate assignment when referencing cc-option

On 17.03.21 г. 0:46 ч., Victor Erminpour wrote:
> Calling cc-option will use KBUILD_CFLAGS, which when lazy setting
> subdir-ccflags-y produces the following build error:
>
> scripts/Makefile.lib:10: *** Recursive variable `KBUILD_CFLAGS' \
> references itself (eventually). Stop.
>
> Use := assignment to subdir-ccflags-y when referencing cc-option.
> This causes make to also evaluate += immediately, cc-option
> calls are done right away and we don't end up with KBUILD_CFLAGS
> referencing itself.
>
> Signed-off-by: Victor Erminpour <[email protected]>
> ---
> fs/btrfs/Makefile | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
> index b634c42115ea..3dba1336fa95 100644
> --- a/fs/btrfs/Makefile
> +++ b/fs/btrfs/Makefile
> @@ -7,10 +7,10 @@ subdir-ccflags-y += -Wmissing-format-attribute
> subdir-ccflags-y += -Wmissing-prototypes
> subdir-ccflags-y += -Wold-style-definition
> subdir-ccflags-y += -Wmissing-include-dirs
> -subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
> -subdir-ccflags-y += $(call cc-option, -Wunused-const-variable)
> -subdir-ccflags-y += $(call cc-option, -Wpacked-not-aligned)
> -subdir-ccflags-y += $(call cc-option, -Wstringop-truncation)
> +subdir-ccflags-y := $(call cc-option, -Wunused-but-set-variable)
> +subdir-ccflags-y := $(call cc-option, -Wunused-const-variable)
> +subdir-ccflags-y := $(call cc-option, -Wpacked-not-aligned)
> +subdir-ccflags-y := $(call cc-option, -Wstringop-truncation)
> # The following turn off the warnings enabled by -Wextra
> subdir-ccflags-y += -Wno-missing-field-initializers
> subdir-ccflags-y += -Wno-sign-compare
>

Why does this patch change only some assignments and others are left as
they were?

2021-03-17 08:44:54

by David Sterba

Subject: Re: [PATCH] btrfs: Use immediate assignment when referencing cc-option

On Tue, Mar 16, 2021 at 03:46:10PM -0700, Victor Erminpour wrote:
> Calling cc-option will use KBUILD_CFLAGS, which when lazy setting
> subdir-ccflags-y produces the following build error:
>
> scripts/Makefile.lib:10: *** Recursive variable `KBUILD_CFLAGS' \
> references itself (eventually). Stop.
>
> Use := assignment to subdir-ccflags-y when referencing cc-option.
> This causes make to also evaluate += immediately, cc-option
> calls are done right away and we don't end up with KBUILD_CFLAGS
> referencing itself.
>
> Signed-off-by: Victor Erminpour <[email protected]>
> ---
> fs/btrfs/Makefile | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/Makefile b/fs/btrfs/Makefile
> index b634c42115ea..3dba1336fa95 100644
> --- a/fs/btrfs/Makefile
> +++ b/fs/btrfs/Makefile
> @@ -7,10 +7,10 @@ subdir-ccflags-y += -Wmissing-format-attribute
> subdir-ccflags-y += -Wmissing-prototypes
> subdir-ccflags-y += -Wold-style-definition
> subdir-ccflags-y += -Wmissing-include-dirs
> -subdir-ccflags-y += $(call cc-option, -Wunused-but-set-variable)
> -subdir-ccflags-y += $(call cc-option, -Wunused-const-variable)
> -subdir-ccflags-y += $(call cc-option, -Wpacked-not-aligned)
> -subdir-ccflags-y += $(call cc-option, -Wstringop-truncation)
> +subdir-ccflags-y := $(call cc-option, -Wunused-but-set-variable)
> +subdir-ccflags-y := $(call cc-option, -Wunused-const-variable)
> +subdir-ccflags-y := $(call cc-option, -Wpacked-not-aligned)
> +subdir-ccflags-y := $(call cc-option, -Wstringop-truncation)

But this overwrites all the previously accumulated values from += so
effectively there's only the last one, no? That's not what we want.