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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -fdebug-prefix-map is not applied to lambda template arguments"
href="https://bugs.llvm.org/show_bug.cgi?id=42237">42237</a>
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<th>Summary</th>
<td>-fdebug-prefix-map is not applied to lambda template arguments
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>All
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>ncalexander@gmail.com
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<pre>With -fdebug-prefix-map specified, I witnessed some paths in debug output that
weren't remapped. I'm not really expert in C++, so it's easiest for me to tell
what my debugging revealed and then try to explain what I think the issue is
and what a test case might look like.
The issue is at
<a href="https://github.com/llvm-mirror/clang/blob/15d397ff14e322428f9d7cda7b9a8d4087ef1b62/lib/CodeGen/CGDebugInfo.cpp#L263">https://github.com/llvm-mirror/clang/blob/15d397ff14e322428f9d7cda7b9a8d4087ef1b62/lib/CodeGen/CGDebugInfo.cpp#L263</a>.
If `printName` includes a type that is itself a C++ lambda, that lambda has a
source location printed. Since `printName` doesn't take a `PrintingPolicy`,
the default `PrintingPolicy` is used, and the default doesn't have the
`RemapFilePaths` flag set.
I think a a minimal test case is a function parameterized by a type that is
itself a lambda with a source location.
In practice, I see this with entries like:
```
operator mozilla::detail::RunnableFunction<(lambda at
/home/nalexander/Mozilla/gecko/dom/audiochannel/AudioChannelService.cpp:745:9)>
*
```
while building Firefox. The code in question can be viewed here:
<a href="https://searchfox.org/mozilla-central/rev/0da35261b6789eec65476dbdd4913df6e235af6d/dom/audiochannel/AudioChannelService.cpp#745">https://searchfox.org/mozilla-central/rev/0da35261b6789eec65476dbdd4913df6e235af6d/dom/audiochannel/AudioChannelService.cpp#745</a>.
It's not trivial to build Firefox so I am happy to dig in to answer follow-up
questions.
I did look at addressing this issue. I see two options:
1) add an optional `PrintingPolicy` parameter to `printName`. I worked up a
patch and used this variant only in `CGDebugInfo.cpp`; it appears to work fine.
2) Make the default `PrintingPolicy` have `RemapFilePaths`. I'm assuming
that's hard due to the rewriting lambda?
2) Make all invocations of `printName` take a `PrintingPolicy`. This seems the
most sensible -- the default policy opens the door to tickets like this -- but
would require somebody with familiarity with clang's codebase to do properly.</pre>
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