[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 only a bunch of reports of the lldb_assert triggering but no actual example that I could turn into a test. rdar://141630334
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@llvm/pr-subscribers-lldb Author: Jonas Devlieghere (JDevlieghere) ChangesA 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 rdar://141630334 Full diff: https://github.com/llvm/llvm-project/pull/123107.diff 1 Files Affected:
diff --git a/lldb/source/Symbol/CompilerType.cpp b/lldb/source/Symbol/CompilerType.cpp
index e9e6e3bf2600ce..3c4390b89a125a 100644
--- a/lldb/source/Symbol/CompilerType.cpp
+++ b/lldb/source/Symbol/CompilerType.cpp
@@ -1105,7 +1105,7 @@ bool CompilerType::GetValueAsScalar(const lldb_private::DataExtractor &data,
return false;
std::optional<uint64_t> byte_size = GetByteSize(exe_scope);
- if (!byte_size)
+ if (!byte_size || *byte_size == 0)
return false;
lldb::offset_t offset = data_byte_offset;
switch (encoding) {
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Jlalond
approved these changes
Jan 15, 2025
| @@ -1105,7 +1105,7 @@ bool CompilerType::GetValueAsScalar(const lldb_private::DataExtractor &data, | |||
| return false; | |||
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|||
| std::optional<uint64_t> byte_size = GetByteSize(exe_scope); | |||
| if (!byte_size) | |||
| if (!byte_size || *byte_size == 0) | |||
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Nit: I would add a comment with brief context on how this appears invalid. Otherwise LGTM
adrian-prantl
approved these changes
Jan 16, 2025
JDevlieghere
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Jan 16, 2025
…lvm#123107) 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 (cherry picked from commit 8965dd4)
adrian-prantl
added a commit
to swiftlang/llvm-project
that referenced
this pull request
Jan 16, 2025
…8965dd40c63c [🍒 swift/release/6.1] [lldb] Handle a byte size of zero in CompilerType::GetValueAsScalar (llvm#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_assertin 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