[Pkg-pascal-devel] Bug#1141144: fp-utils-3.2.2: fpdoc does not build .chm files reproducibly

[Peter Blackman]

On 27/06/2026 16:02, peter green wrote:
> On 27/06/2026 15:47, Mazen Neifer wrote:
> 
>> I've tried to investigate this issues and came to the following conclusion based on multiple analysis about what is causing the non-reproducibility in the |lcl.chm| build.
>>
>> The Compiled HTML Help (CHM) generation process uses FPC's built-in |chmwriter.pas| (which is compiled into the |fpdoc| utility). It has two runtime calls to |*SysUtils.Now*| that embed timestamps into the binary:
>>
>>  1. *CHM Header:* |*TITSFWriter.InitITSFHeader*| sets |*TimeStamp := NToBE(MilliSecondOfTheDay(Now));*|
>>  2. *System Stream:* |*TChmWriter.WriteSYSTEM*| sets a metadata entry with |*FSection0.WriteDWord(NToLE(MilliSecondOfTheDay(Now)));*|
>>
>> Because these calls use the system clock at runtime, the generated CHM files differ byte-for-byte depending on the exact millisecond they are built. Setting the |*SOURCE_DATE_EPOCH*| environment variable has no effect because |*SysUtils.Now*| is a standard FPC runtime function and does not read it.--
>>
> So presumablly the fix would be to patch said generator so it does understand
> SOURCE_DATE_EPOCH.


Using SOURCE_DATE_EPOCH was part of the solution,
but there were also several instances of uninitialised stack variables,
which caused some random bytes to appear in the .chm files.

Full story here;
https://gitlab.com/freepascal.org/fpc/source/-/work_items/41803