From mboxrd@z Thu Jan  1 00:00:00 1970
Subject: What is a "NULL" library class?
To: devel@edk2.groups.io
From: wonderfly@waymo.com
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Date: Thu, 28 Jan 2021 10:21:58 -0800
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Hi,

I am super new to EDK2 development so excuse my ignorance.=C2=A0 While bro=
wsing the code base I find a lot places where the keyword "NULL" is used in=
 place of a LibraryClass, specifically in DSC files.=C2=A0 For example,

in edk2/UefiPayloadPkg/UefiPayloadPkgIa32.dsc:
MdeModulePkg/Core/Dxe/DxeMain.inf {
<LibraryClasses>
NULL|MdeModulePkg/Library/LzmaCustomDecompressLib/LzmaCustomDecompressLib.=
inf
}

What does this mean?=C2=A0 Does it mean that the=C2=A0LzmaCustomDecompress=
Lib.inf library instance is unconditionally linked for this package?

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Hi,<br /><br />I am super new to EDK2 development so excuse my ignorance.&n=
bsp; While browsing the code base I find a lot places where the keyword "NU=
LL" is used in place of a LibraryClass, specifically in DSC files.&nbsp; Fo=
r example,<br /><br />
<div>in edk2/UefiPayloadPkg/UefiPayloadPkgIa32.dsc:&nbsp; &nbsp; &nbsp; &n=
bsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; =
&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp=
; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nb=
sp;</div>
<div>&nbsp; MdeModulePkg/Core/Dxe/DxeMain.inf {</div>
<div>&nbsp; &nbsp; &lt;LibraryClasses&gt;</div>
<div>&nbsp; &nbsp; &nbsp; NULL|MdeModulePkg/Library/LzmaCustomDecompressLi=
b/LzmaCustomDecompressLib.inf</div>
<div>&nbsp; }<br /><br />What does this mean?&nbsp; Does it mean that the&=
nbsp;LzmaCustomDecompressLib.inf library instance is unconditionally linked=
 for this package?</div>

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