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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - lldb doesn't find locationless variables in abstract origin of inlined functions"
href="https://bugs.llvm.org/show_bug.cgi?id=50076">50076</a>
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<th>Summary</th>
<td>lldb doesn't find locationless variables in abstract origin of inlined functions
</td>
</tr>
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<th>Product</th>
<td>lldb
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>lldb-dev@lists.llvm.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>jeremy.morse.llvm@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>cristianassaiante@outlook.com, dblaikie@gmail.com, jdevlieghere@apple.com, llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Hi lldb folks,
I believe lldb isn't "seeing" variables that appear only in the abstract
origins of DW_TAG_inlined_subroutines. Over in <a href="https://reviews.llvm.org/D95617">https://reviews.llvm.org/D95617</a>
we started omitting variables that have no location, i.e. never emitting things
like:
DW_TAG_formal_parameter
DW_AT_abstract_origin (0x0000005a "bar")
by themselves, instead expecting the consumer to look in the
DW_TAG_inlined_subroutine's abstract origin for it. It appears that lldb
doesn't do this, while gdb does. Specifically, if you take the reproducer for
<a class="bz_bug_link
bz_status_NEW "
title="NEW - Missing variables after inlining pass at O3"
href="show_bug.cgi?id=49973">bug 49973</a> and revert D95617, lldb produces different error messages when it
can't find an optimised out variable, here's a long script:
$ clang --version
clang version 13.0.0 (<a href="mailto:git@github.com">git@github.com</a>:llvm/llvm-project
e6eaacbf0bd0c76a4fbfbd30c6159f57a89b3480)
Target: x86_64-unknown-linux-gnu
$ clang -o a.out -g -O3 lib/test.c a.c
[some warnings]
$ lldb --version
lldb version 13.0.0 (<a href="mailto:git@github.com">git@github.com</a>:llvm/llvm-project revision
e6eaacbf0bd0c76a4fbfbd30c6159f57a89b3480)
clang revision e6eaacbf0bd0c76a4fbfbd30c6159f57a89b3480
llvm revision e6eaacbf0bd0c76a4fbfbd30c6159f57a89b3480
$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/tmp/faces/a.out' (x86_64).
(lldb) b main
Breakpoint 1: where = a.out`main + 11 [inlined] c + 10 at a.c:9:1, address =
0x000000000040056b
(lldb) process launch
Process 14037 launched: '/tmp/faces/a.out' (x86_64)
Process 14037 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x000000000040056b a.out`main [inlined] c at a.c:9:1
6 int l_128 = b = 4;
7 for (; b ; b = 0)
8 l_128 = 1;
-> 9 test_nop();
10 test_support_3008(l_128);
11 }
12 int main ()
(lldb) p l_128
error: <user expression 0>:1:1: use of undeclared identifier 'l_128'
l_128
^
(lldb) ^D
$ git revert 1d68e0a0756476ceee1e62a778021e339c631940
$ ninja ./bin/clang ./bin/opt ./bin/llc ./bin/lldb
$ clang -o a.out -g -O3 lib/test.c a.c
[some warnings]
$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/tmp/faces/a.out' (x86_64).
(lldb) b main
Breakpoint 1: where = a.out`main + 11 [inlined] c + 10 at a.c:9:1, address =
0x000000000040056b
(lldb) process launch
Process 14683 launched: '/tmp/faces/a.out' (x86_64)
Process 14683 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x000000000040056b a.out`main [inlined] c at a.c:9:1
6 int l_128 = b = 4;
7 for (; b ; b = 0)
8 l_128 = 1;
-> 9 test_nop();
10 test_support_3008(l_128);
11 }
12 int main ()
(lldb) print l_128
error: Couldn't materialize: couldn't get the value of variable l_128: no
location, value may have been optimized out
error: errored out in DoExecute, couldn't PrepareToExecuteJITExpression
(lldb)
~
tl;dr: lldb produces "value may have been optimized out" before D95617 lands,
"undeclared identifier" afterwards. gdb produces "optimized out" in all
scenarios.
We were pretty confident in
<a href="https://lists.llvm.org/pipermail/llvm-dev/2021-January/148165.html">https://lists.llvm.org/pipermail/llvm-dev/2021-January/148165.html</a> that the
DWARF is fine.</pre>
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