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clarify linkonce/weak linkage

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llvm-svn: 33201
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Chris Lattner 2007-01-14 06:51:48 +00:00
parent 69b1c31416
commit ad0711b2eb
1 changed files with 10 additions and 7 deletions
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@ -424,23 +424,26 @@ All Global Variables and Functions have one of the following types of linkage:
an internal global value may cause the internal to be renamed as necessary to an internal global value may cause the internal to be renamed as necessary to
avoid collisions. Because the symbol is internal to the module, all avoid collisions. Because the symbol is internal to the module, all
references can be updated. This corresponds to the notion of the references can be updated. This corresponds to the notion of the
'<tt>static</tt>' keyword in C, or the idea of "anonymous namespaces" in C++. '<tt>static</tt>' keyword in C.
</dd> </dd>
<dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt> <dt><tt><b><a name="linkage_linkonce">linkonce</a></b></tt>: </dt>
<dd>"<tt>linkonce</tt>" linkage is similar to <tt>internal</tt> linkage, with <dd>Globals with "<tt>linkonce</tt>" linkage are merged with other globals of
the twist that linking together two modules defining the same the same name when linkage occurs. This is typically used to implement
<tt>linkonce</tt> globals will cause one of the globals to be discarded. This inline functions, templates, or other code which must be generated in each
is typically used to implement inline functions. Unreferenced translation unit that uses it. Unreferenced <tt>linkonce</tt> globals are
<tt>linkonce</tt> globals are allowed to be discarded. allowed to be discarded.
</dd> </dd>
<dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt> <dt><tt><b><a name="linkage_weak">weak</a></b></tt>: </dt>
<dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage, <dd>"<tt>weak</tt>" linkage is exactly the same as <tt>linkonce</tt> linkage,
except that unreferenced <tt>weak</tt> globals may not be discarded. This is except that unreferenced <tt>weak</tt> globals may not be discarded. This is
used to implement constructs in C such as "<tt>int X;</tt>" at global scope. used for globals that may be emitted in multiple translation units, but that
are not guaranteed to be emitted into every translation unit that uses them.
One example of this are common globals in C, such as "<tt>int X;</tt>" at
global scope.
</dd> </dd>
<dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt> <dt><tt><b><a name="linkage_appending">appending</a></b></tt>: </dt>