RE: [PATCH] kbuild: single-quote the format string of printf

2023-08-30 Thread David Laight
...
> All of "\\n", "\n", '\n' are the same.

and \\n (without any quote characters at all).

Personally I'd use 'format' for printf.
To make it obvious that nothing is to be expanded.
But it isn't really worth changing existing 'stuff'.

David

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Re: [PATCH] kbuild: single-quote the format string of printf

2023-08-30 Thread Masahiro Yamada
On Wed, Aug 30, 2023 at 10:00 AM Nicolas Schier  wrote:
>
> On Tue 29 Aug 2023 20:35:31 GMT, Masahiro Yamada wrote:
> > Use single-quotes to avoid escape sequences (\\n).
> >
> > Signed-off-by: Masahiro Yamada 
> > ---
>
> Is this really necessary?  Testing w/ GNU Make 4.3, bash 5.2.15 or
> dash 0.5.12-6 and a stupid Makefile snippet I cannot see any difference
> between these three:
>
> print:
> @printf "hello med single-backslash and double quotes\n"
> @printf 'hello med single-backslash and single quotes\n'
> @printf "hello med double-backslash and double quotes\\n"
>
> Only double-backslash+n in single-quotes does not work, for obvious
> reasons.


You are right.

I was misunderstanding the backslash-escaping in double-quotes.

I always used single-quotes when I wanted to avoid
escape sequences.

The following POSIX spec applies here:


  2.2.3 Double-Quotes

  The  shall retain its special meaning as an escape character
  (see Escape Character (Backslash)) only when followed by one of the
  following characters when considered special:

  $   `   "   \   




https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html


All of "\\n", "\n", '\n' are the same.



-- 
Best Regards
Masahiro Yamada


Re: [PATCH] kbuild: single-quote the format string of printf

2023-08-29 Thread Nicolas Schier
On Tue 29 Aug 2023 20:35:31 GMT, Masahiro Yamada wrote:
> Use single-quotes to avoid escape sequences (\\n).
> 
> Signed-off-by: Masahiro Yamada 
> ---

Is this really necessary?  Testing w/ GNU Make 4.3, bash 5.2.15 or
dash 0.5.12-6 and a stupid Makefile snippet I cannot see any difference 
between these three:

print:
@printf "hello med single-backslash and double quotes\n"
@printf 'hello med single-backslash and single quotes\n'
@printf "hello med double-backslash and double quotes\\n"

Only double-backslash+n in single-quotes does not work, for obvious 
reasons.

Is this some compatibility to older make versions or other shells?

Iff it is, we should have several cases that are actually broken right 
now:

$ git grep -Hrne 'printf.*".*\\n' '**/Makefile*' '**/Kbuild*' 
arch/mips/Makefile:480:   printf "  %-24s - Build generic kernel for $(call 
describe_generic_defconfig,$(cfg))\n" $(cfg);)
arch/mips/Makefile:486:   printf "  %-24s - Build $($(cfg)-y)\n" $(cfg);)
samples/bpf/Makefile:238:HDR_PROBE := $(shell printf "$(pound)include 
\n struct list_head { int a; }; int main() { return 0; }" | \
samples/hid/Makefile:76:HDR_PROBE := $(shell printf "$(pound)include 
\n struct list_head { int a; }; int main() { return 0; }" | \
scripts/Makefile.compiler:41:   printf "%b\n" "$(1)" | $(CC) -Werror 
$(CLANG_FLAGS) $(KBUILD_AFLAGS) -c -x assembler-with-cpp -o "$$TMP" -,$(2),$(3))
scripts/Makefile.lib:437:printf "%08x\n" $$dec_size |   
\
scripts/Makefile.modfinal:43:   printf "Skipping BTF generation for %s 
due to unavailability of vmlinux\n" $@ 1>&2; \
scripts/Makefile.modfinal:45:   printf "Skipping BTF generation for %s 
because it's a Rust module\n" $@ 1>&2; \
security/tomoyo/Makefile:11:printf '\t"";\n';) \
tools/testing/selftests/Makefile:263:   [ ! -d $(INSTALL_PATH)/$$TARGET 
] && printf "Skipping non-existent dir: $$TARGET\n" && continue; \
tools/testing/selftests/Makefile:264:   printf "Emit Tests for 
$$TARGET\n"; \
tools/testing/selftests/nolibc/Makefile:136: if (s+f > 0) printf(" 
See all results in %s\n", ARGV[1]); else print; }' \
tools/testing/selftests/nolibc/Makefile:155: if (s+f > 0) printf(" 
See all results in %s\n", ARGV[1]); else print; }' \
tools/testing/selftests/nolibc/Makefile:163: if (s+f > 0) printf(" 
See all results in %s\n", ARGV[1]); else print; }' \
tools/testing/selftests/wireguard/qemu/Makefile:335:printf 
'CONFIG_NR_CPUS=$(NR_CPUS)\nCONFIG_INITRAMFS_SOURCE="$(BUILD_PATH)/init-cpio-spec.txt"\n'
 >> $(KERNEL_BUILD_PATH)/minimal.config

I assume, that changing '\\n' occurrences in all Makefiles to '\n' 
should be enough; but only a cosmetic change.  Or did I miss some
point?

Kind regards,
Nicolas


> 
>  Makefile  | 8 
>  arch/powerpc/Makefile | 2 +-
>  2 files changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 87a9eef3fb4b..d09600f7a036 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -1643,12 +1643,12 @@ help:
>   @echo  ''
>   @$(if $(boards), \
>   $(foreach b, $(boards), \
> - printf "  %-27s - Build for %s\\n" $(b) $(subst 
> _defconfig,,$(b));) \
> + printf '  %-27s - Build for %s\n' $(b) $(subst 
> _defconfig,,$(b));) \
>   echo '')
>   @$(if $(board-dirs), \
>   $(foreach b, $(board-dirs), \
> - printf "  %-16s - Show %s-specific targets\\n" help-$(b) $(b);) 
> \
> - printf "  %-16s - Show all of the above\\n" help-boards; \
> + printf '  %-16s - Show %s-specific targets\n' help-$(b) $(b);) \
> + printf '  %-16s - Show all of the above\n' help-boards; \
>   echo '')
>  
>   @echo  '  make V=n   [targets] 1: verbose build'
> @@ -1684,7 +1684,7 @@ $(help-board-dirs): help-%:
>   @echo  'Architecture specific targets ($(SRCARCH) $*):'
>   @$(if $(boards-per-dir), \
>   $(foreach b, $(boards-per-dir), \
> - printf "  %-24s - Build for %s\\n" $*/$(b) $(subst 
> _defconfig,,$(b));) \
> + printf '  %-24s - Build for %s\n' $*/$(b) $(subst 
> _defconfig,,$(b));) \
>   echo '')
>  
>  
> diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
> index dac7ca153886..f49ac05eae20 100644
> --- a/arch/powerpc/Makefile
> +++ b/arch/powerpc/Makefile
> @@ -353,7 +353,7 @@ define archhelp
>echo '  (minus the .dts extension).'
>echo
>$(foreach cfg,$(generated_configs),
> -printf "  %-27s - Build for %s\\n" $(cfg) $(subst _defconfig,,$(cfg));)
> +printf '  %-27s - Build for %s\n' $(cfg) $(subst _defconfig,,$(cfg));)
>  endef
>  
>  PHONY += install
> -- 
> 2.39.2


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