Re: [edk2-devel] [PATCH edk2-InfSpecification] Drop statement on package ordering

["Leif Lindholm" <leif@nuviainc.com>]

Hi Mike,

Ok, I'm happy to hear that.

I agree that the overriding behaviour is useful, and it would be good
to document it. The problem is that the current wording does not say
that (in a way that is useful to anyone who does not already know what
it means). And the MdePkg/MdeModulePkg example sounds positively
horrific when interpreted in this light.

Clearly, my proposed modification is not the right thing to do here.

The problem with the document implying that the order should reflect
some sort of hierarchy *apart from when explicitly overriding* is that
this is asking a human to do the thing that humans are bad at and
computers are good at. It can't scale where humans are reviewing ports
that they understand less well than the people contributing them.

I think we should find a wording that explains the behaviour instead
of explaining some potential derivative of the behaviour, as well as
providing a realistic example instead of the MdePkg/MdeModulePkg
statament.

My suggestion is to keep it simple: say something like "where there is
a need to override an include file provided by one package with one
provided by another package, know that the compiler invocation will
list the include directories in the same order as the .dec files are
listed in the .inf".

Regards,

Leif

On Sun, May 31, 2020 at 22:19:24 +0000, Michael D Kinney wrote:
> Hi Leif,
> 
> The reason for this statement is not for performance.
> 
> It is if the same include file exists in the same path
> in more than one package.  Defining this behavior makes
> the build system deterministic.
> 
> There is use case where a platform package can provide
> an include override of a common package and the platform
> modules list the platform package before the common
> package in the [Packages] section.
> 
> So deterministic build when there are include file 
> name collisions and overrides are 2 reasons to keep
> the currently defined behavior.
> 
> With this background, perhaps some clarification or
> rewording of the spec is required?  Do you have suggestions?
> 
> Thanks,
> 
> Mike
> 
>   This is not a common use case,
> but one that does apply is a platform module that wants
> to use an override of a standard include file in a platform
> package.
> 
> For the build system autogen stage, this statement 
> 
> Mike
> 
> > -----Original Message-----
> > From: Leif Lindholm <leif@nuviainc.com>
> > Sent: Friday, May 29, 2020 7:03 AM
> > To: devel@edk2.groups.io
> > Cc: Kinney, Michael D <michael.d.kinney@intel.com>;
> > Andrew Fish <afish@apple.com>; Laszlo Ersek
> > <lersek@redhat.com>; Pankaj Bansal
> > <pankaj.bansal@oss.nxp.com>
> > Subject: [PATCH edk2-InfSpecification] Drop statement
> > on package ordering
> > 
> > The description of [Packages] sections stated that
> > "Packages must be listed in the order that may be
> > required for specifying
> >  include path statements for a compiler. For example,
> > the
> >  MdePkg/MdePkg.dec file must be listed before the
> >  MdeModulePkg/MdeModulePkg.dec file."
> > 
> > Drop it.
> > 
> > Signed-off-by: Leif Lindholm <leif@nuviainc.com>
> > ---
> > 
> > Surely this isn't something we take seriously?
> > If there is a measurable performance impact to the
> > order of -I option
> > on the compiler command line, we should approach this
> > programmatically.
> > 
> >  3_edk_ii_inf_file_format/37_[packages]_sections.md | 7
> > ++-----
> >  1 file changed, 2 insertions(+), 5 deletions(-)
> > 
> > diff --git
> > a/3_edk_ii_inf_file_format/37_[packages]_sections.md
> > b/3_edk_ii_inf_file_format/37_[packages]_sections.md
> > index 17a8d91..c09112b 100644
> > ---
> > a/3_edk_ii_inf_file_format/37_[packages]_sections.md
> > +++
> > b/3_edk_ii_inf_file_format/37_[packages]_sections.md
> > @@ -42,11 +42,8 @@ Defines the `[Packages]` section tag
> > that is used in EDK II module INF files.
> >  Each entry in this section contains a directory name,
> > forward slash character
> >  and the name of the DEC file contained in the
> > directory name.
> > 
> > -Packages must be listed in the order that may be
> > required for specifying
> > -include path statements for a compiler. For example,
> > the _MdePkg/MdePkg.dec_
> > -file must be listed before the
> > `MdeModulePkg/MdeModulePkg.dec` file. If there
> > -are PCDs listed in the generated "As Built" INF, the
> > packages that declare any
> > -PCDs must be listed in this section.
> > +If there are PCDs listed in the generated "As Built"
> > INF, the packages that
> > +declare any PCDs must be listed in this section.
> > 
> >  Each package filename must be listed only once per
> > section. Package filenames
> >  listed in architectural sections are not permitted to
> > be listed in the common
> > --
> > 2.20.1
> 
> 
> 
>