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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Optional Parameter Argument Preprocessor trick fails for objc_method_family (init) methods"
href="https://bugs.llvm.org/show_bug.cgi?id=45245">45245</a>
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<th>Summary</th>
<td>Optional Parameter Argument Preprocessor trick fails for objc_method_family (init) methods
</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>Macintosh
</td>
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<th>OS</th>
<td>MacOS X
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>dmaclach@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>Created <span class=""><a href="attachment.cgi?id=23256" name="attach_23256" title="Code for repro case.">attachment 23256</a> <a href="attachment.cgi?id=23256&action=edit" title="Code for repro case.">[details]</a></span>
Code for repro case.
There is a "trick" described at
<a href="https://stackoverflow.com/questions/3046889/optional-parameters-with-c-macros">https://stackoverflow.com/questions/3046889/optional-parameters-with-c-macros</a>
for doing optional parameters with c macros.
It is used by the popular <a href="https://ocmock.org/">https://ocmock.org/</a> library.
Unfortunately it seems to generate a warning for unused-value that it shouldn't
generate when used with an objc_method_family (init) from within an objc method
implementation.
To repro:
Xcode 11.3 (or Xcode 11.4b3)
clang -Werror -Wunused-value -fobjc-arc main.m
Expected Result: Clean compile
Actual Result:
main.m:30:13: error: expression result unused [-Werror,-Wunused-value]
OCMVerify([object init]);
^~~~~~~~~~~~~
main.m:12:64: note: expanded from macro 'OCMVerify'
#define OCMVerify(...) _OCMVerify_X(,##__VA_ARGS__, _OCMVerify(__VA_ARGS__))
^~~~~~~~~~~
main.m:8:5: note: expanded from macro '_OCMVerify'
invocation; \
^~~~~~~~~~
main.m:11:39: note: expanded from macro '_OCMVerify_X'
#define _OCMVerify_X(x,A,FUNC, ...) FUNC</pre>
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