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Re: timestamp_t bit width


Hi JP,

I’m afraid I just move the decl (and its comment) from another file.  It appears the author
was Henner Zeller in 3f57fa5d2443a085c9fa243c615d71dc470a0107.  

Commit comment was: 

    Change time_t in the functions that deal with timestamps to a new 
    typedef timestamp_t (defined as a long).
    that makes sure the c++ side and swigged Python side agree on the 
    type, because time_t create problems in Python scripts.


> On 25 Mar 2019, at 15:51, jp charras <jp.charras@xxxxxxxxxx> wrote:
> Le 25/03/2019 à 16:22, Wayne Stambaugh a écrit :
>> On 3/24/2019 2:34 PM, Seth Hillbrand wrote:
>>> Am 2019-03-24 13:23, schrieb Jon Evans:
>>>> Hi all,
>>>> Another question from this forum thread:
>>>> https://forum.kicad.info/t/before-giving-up-on-kicad-one-last-attempt-erc-misery/15933/67
>>>> timestamp_t is defined as "long", with a note that swig can't handle
>>>> int32_t.
>>> I don't understand this comment.  SWIG includes stdint.i which
>>> explicitly defines the exact integral types.  Maybe Jeff can shed some
>>> light here?
>>>> This means that timestamp_t will be 32-bit on many platforms, but
>>>> 64-bit on Linux and MacOS running on 64-bit hardware.  Apparently
>>>> there is at least one bug here involving the Eagle importer writing
>>>> out library files with 64-bit timestamps, which 32-bit KiCad cannot
>>>> open.
>>> This is a problem in ParseHex().  If it gets a hex value that overflows,
>>> it throws an error, stopping the processing.  So this isn't specific to
>>> the Eagle plugin but rather a 32-bit/64-bit issue.  We allow 64-bit to
>>> be written to file but only generate a time_t (32-bit) value for new,
>>> internal stamps.
>>> The Eagle processor creates its own "timestamp" by hash which is 64 bits
>>> on a 64 bit machine.
>> Do you mean our Eagle plugins are not truncating 64 bit time stamps in
>> Eagle files?  If so, the problem needs to be fixed here.  AFAIK, KiCad
>> has always used 32 bit time stamps.
> The issue is the fact the legacy plugin currently uses a long as time
> stamp, but do not truncate if to 32 bits when writing a .sch file.
> So because Eagle importer generate a long value, the legacy plugin
> writes 8 hexa chars on 32 bits platform, but can write more than 8 chars
> on 64 bits platforms
>>>> Q1: Is there actually a bug here? maybe someone more familiar with the
>>>> Eagle importer can take a look.
>>> Yes.  Definitely bug.  We should be trimming the hash-based timestamp to
>>> 32-bits.
>> You would also have to add checking for duplicate time stamps due to the
>> truncation of the upper 32 bits.
>>>> Q2: Shouldn't we change the type of timestamp_t to be either "int" (if
>>>> we want it to be 32-bit) or "long long" (if we want it to be 64-bit)?
>>> I think 32-bits is the correct way to go here and using uint32_t should
>>> work but I may be missing an important detail.
>>>> My first thought is that we should change timestamp_t to be 32-bit on
>>>> all platforms, but I'm not sure the best way to handle existing files
>>>> that have been written out with 64-bit timestamps.
>>> This is problematic.  I think we could patch the reader to handle 64-bit
>>> values but store 32-bit.
>>> -Seth
> I have a fix for that (it forces 32 bits in timestamp_t and allows 64
> bits when reading a file).
> Annotation should already take care of duplicate timestamps (and replace
> duplicates if any) unless bug.
> The right fix is to use uint32_t for timestamps, at least for the
> current file format.
> @Jeff, you added a comment in common.h about an issue with Swig.
> What is this issue you encountered when using uint32_t as typedef for
> timestamp_t with swig (I did not see an issue during my tests)?
> -- 
> Jean-Pierre CHARRAS

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