[PATCH] D78952: [LangRef] Describe linkage types, allocation size of declarations for global variables

[Matthias Schiffer via Phabricator via llvm-commits]

NeoRaider created this revision.
NeoRaider added reviewers: jdoerfert, efriedma.
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Linkage type was only referenced for functions, not for global variables.

      

Clarify that LLVM doesn't make assumption about the allocation size when no definitive initializer for a global variable is known.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D78952

Files:
  llvm/docs/LangRef.rst


Index: llvm/docs/LangRef.rst
===================================================================
--- llvm/docs/LangRef.rst
+++ llvm/docs/LangRef.rst
@@ -272,8 +272,8 @@
     visible, meaning that it participates in linkage and can be used to
     resolve external symbol references.
 
-It is illegal for a function *declaration* to have any linkage type
-other than ``external`` or ``extern_weak``.
+It is illegal for a global variable or function *declaration* to have any
+linkage type other than ``external`` or ``extern_weak``.
 
 .. _callingconv:
 
@@ -615,6 +615,8 @@
 Global variables in other translation units can also be declared, in which
 case they don't have an initializer.
 
+Global variables can optionally specify a :ref:`linkage type <linkage>`.
+
 Either global variable definitions or declarations may have an explicit section
 to be placed in and may have an optional explicit alignment specified. If there
 is a mismatch between the explicit or inferred section information for the
@@ -686,6 +688,11 @@
 iterate over them as an array, alignment padding would break this
 iteration. The maximum alignment is ``1 << 29``.
 
+For global variables *declarations*, as well as definitions that may be
+replaced at link time (``linkonce``, ``weak``, ``extern_weak`` and ``common``
+linkage types), LLVM makes no assumptions whatsoever regarding the allocation
+size of the variable.
+
 Globals can also have a :ref:`DLL storage class <dllstorageclass>`,
 an optional :ref:`runtime preemption specifier <runtime_preemption_model>`,
 an optional :ref:`global attributes <glattrs>` and


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