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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Variables named `_` should not trigger -Wunused-parameter"
href="http://llvm.org/bugs/show_bug.cgi?id=15859">15859</a>
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<th>Summary</th>
<td>Variables named `_` should not trigger -Wunused-parameter
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>All
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>kenneth@ballenegger.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>It is common convention in other programming languages to use the variable name
`_` for unused parameters. In C, with blocks for callbacks, and in Objective-C
when using the delegation pattern, there are many valid use cases in which one
would not use a parameter (eg. when your block type / method signature is
defined in a third party api).
I think it would be best not to trigger the `unused-parameter` warning for
variables named `_`. That would enable users of the API to specify their
intention to actually not use the variable.
For example:
- (IBAction)someAction:(id)_ { // <- warning, unused parameter
printf("Hello, world!\n");
}
Or:
// In an API:
void calculate_something(MyBlock callback);
typedef void(^MyBlock)(int, char *info_message);
// In end-developer code:
{
calculate_something(^(int i, char *_) { // <- warning
printf("Int is: %d\n", i);
});
}</pre>
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