AW: RE: Keeping last-modified dates

Steve Fairhead <mailto:steve@fivetrees.com> schrieb am Dienstag, 29. August 2006 18:18:

> Greg Thomas said:
>
>>>
> On Tue, 29 Aug 2006 14:36:24 +0100, "Andrew Webb"
> <andrew.microi@gmail.com> wrote:
>
>> As Steve Fairhead says in a recent, related thread: "one could argue
>> just as hard for timestamps to be preserved *because* of makefiles".
>
> You could try, but I don't think you would be very successful. If you
> preserve modification times, you fall in to the following trap:
>
> 1-Aug: Alice checks out file foo.c, modification date 1-Aug.
> 2-Aug: Bob modifies, commits foo.c
> 3-Aug: Alice does a make. foo.c is compiled,
> creating foo.o timestamped 3-aug.
> 4-Aug: Alice does a 'svn update'. foo.c arrives timestamped 2-Aug
> Alice does a make. foo.c is not compiled, despite being
> changed since the last compilation, as foo.c is timestamped
> 2-Aug (when Bob made the change), which is before foo.o was
> created (3-Aug). <<
>
> This is fairly bogus. So Alice has edited a file, thrown it away, and
> reverted to an earlier version. With or without a VCS, this
> is (as I said
> earlier in another post) the sort of situation that breaks
> makefiles anyway.
> I'd do a make clean.

No, she did neither throw away any changes nor did she revert to an older version. It just happens that the newer version of foo.c was commited bevore she did a build in her working copy. After that she made an svn update, retrieving the newest version of foo.c but as it gets Bobs last-modified date the file is "older" than the compiled version, breaking the contract that "make" relies on. The way subversion behaves now, Alice would get a modification time of 08/04/2006 which honors the contract that make relies on (modified source files are supposed to be newer than the compiled versions).

Running a "make clean" for every build is only possible where build times are small enough or it will impact your productiveness.

>
> Steve
> http://www.sfdesign.co.uk
> http://www.fivetrees.com
>
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felix

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Felix Gilcher
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