[Buildroot] [PATCH 03/16 v3] core/pkg-utils: add macro to hardlink-or-copy

[Arnout Vandecappelle <arnout@mind.be>]

On 01-02-16 11:13, Luca Ceresoli wrote:
> Hi,
> 
> Arnout Vandecappelle wrote:
>> On 28-01-16 19:15, Yann E. MORIN wrote:
>>> This macro will try to copy a source file into a destination fdirectory,
>>> by first atempting a hard-link, and falling back to a plain copy.
>>>
>>> In some situations, it will be necessary that the destination file is
>>> named differently than the source (e.g. due to a re-numbering), so if a
>>> third argument is specified, it is treated as the basename of the
>>> destination file.
>>>
>>> Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
>>> Cc: Luca Ceresoli <luca@lucaceresoli.net>
>>>
>>> ---
>>> Changes v2 -> v3;
>>>    - use "ln" instead of "cp -l"
>>>    - accept third argument, as the basename of the destination file
>>>    - drop reviewed-by and tested-by tags given in v2, due to the above
>>>      two changes
>>>
>>> Changes RFC -> v1:
>>>    - move to pkg-utils  (Luca)
>>> ---
>>>   package/pkg-utils.mk | 25 +++++++++++++++++++++++++
>>>   1 file changed, 25 insertions(+)
>>>
>>> diff --git a/package/pkg-utils.mk b/package/pkg-utils.mk
>>> index 44bd2c9..6479cd8 100644
>>> --- a/package/pkg-utils.mk
>>> +++ b/package/pkg-utils.mk
>>> @@ -113,6 +113,31 @@ $$(error Package error: use $(2) instead of $(1). Please
>>> fix your .mk file)
>>>   endif
>>>   endef
>>>
>>> +################################################################################
>>>
>>> +# hardlink-copy -- hardlink source and destination if possible, otherwise
>>> +# do a simple copy
>>> +#
>>> +# argument 1 is the source *file*
>>> +# argument 2 is the destination *directory*
>>> +# argument 3 is the basename of the destination file (optional, defaults to
>>> +#            the basename of the source file.
>>> +#
>>> +# examples:
>>> +#   $(call hardlink-copy,/path/to/source/file,/path/to/destination/dir/)
>>> +#   $(call
>>> hardlink-copy,/path/to/source/file,/path/to/destination/dir/,new-name)
>>> +#
>>> +# Note: we make that a single command, so se can:
>>> +#  - use '$(Q)' in front of it and properly silence the whole macro,
>>> +#  - use '|| exit 1' after it, so we can exit on error in compound commands.
>>> +################################################################################
>>>
>>> +define hardlink-copy
>>> +    { mkdir -p $(2) && \
>>> +        { ln $(1) $(2)$(if $(3),/$(strip $(3))) 2>/dev/null || \
>>
>>   Shouldn't this be ln -f (and maybe cp -f) to make sure it behaves the same when
>> you run it a second time?
> 
> Indeed it's true. Not an issue for 'make legal-info' since it wipes the
> output dir before copying file in it, but the macro is generic so it
> has to handle this case.
> 
> This definitely applies to ln. cp normally doesn't need it, but it does
> not hurt.

 With -f, cp will indeed only unlink if it can't write; if the target is a
symlink, it will still not remove the symlink but instead it will overwrite the
file pointed to. So an explicit rm -f is probably better.

 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
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