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[lldb] Handle a byte size of zero in CompilerType::GetValueAsScalar (#123107)

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A bit or byte size of 0 is not a bug. It can legitimately (and
frequently) happen in Swift and C, just not in C++. However, it doesn't
make sense to read a scalar of zero bytes.

Currently, when this happens, we trigger an `lldb_assert` in the data
extractor and return 0, which isn't accurate. I have a bunch of reports
of the assert triggering, but nobody has been able to provide me with a
reproducer that I can turn into a test and I wasn't able to concoct a
test case by reverse-engineering the code.

rdar://141630334
This commit is contained in:
Jonas Devlieghere
2025-01-16 09:33:59 -08:00
committed by GitHub
parent 60e4d24963
commit 8965dd40c6
1 changed files with 4 additions and 1 deletions
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5
lldb/source/Symbol/CompilerType.cpp
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@@ -1105,8 +1105,11 @@ bool CompilerType::GetValueAsScalar(const lldb_private::DataExtractor &data,
return false;
std::optional<uint64_t> byte_size = GetByteSize(exe_scope);
if (!byte_size)
// A bit or byte size of 0 is not a bug, but it doesn't make sense to read a
// scalar of zero size.
if (!byte_size || *byte_size == 0)
return false;
lldb::offset_t offset = data_byte_offset;
switch (encoding) {
case lldb::eEncodingInvalid: