Make CompilerType::getBitSize() / getByteSize() return an optional result. NFC
The code in LLDB assumes that CompilerType and friends use the size 0
as a sentinel value to signal an error. This works for C++, where no
zero-sized type exists, but in many other programming languages
(including I believe C) types of size zero are possible and even
common. This is a particular pain point in swift-lldb, where extra
code exists to double-check that a type is *really* of size zero and
not an error at various locations.
To remedy this situation, this patch starts by converting
CompilerType::getBitSize() and getByteSize() to return an optional
result. To avoid wasting space, I hand-rolled my own optional data
type assuming that no type is larger than what fits into 63
bits. Follow-up patches would make similar changes to the ValueObject
hierarchy.
rdar://problem/47178964
Differential Revision: https://reviews.llvm.org/D56688
llvm-svn: 351214
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp
index 0cdb0b2..0d39e5a 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp
@@ -79,17 +79,22 @@
CompilerType type;
ValueObjectSP chunk;
// For small bitsets __first_ is not an array, but a plain size_t.
- if (m_first->GetCompilerType().IsArrayType(&type, nullptr, nullptr))
- chunk = m_first->GetChildAtIndex(
- idx / type.GetBitSize(ctx.GetBestExecutionContextScope()), true);
- else {
+ if (m_first->GetCompilerType().IsArrayType(&type, nullptr, nullptr)) {
+ auto bit_size = type.GetBitSize(ctx.GetBestExecutionContextScope());
+ if (!bit_size || *bit_size == 0)
+ return {};
+ chunk = m_first->GetChildAtIndex(idx / *bit_size, true);
+ } else {
type = m_first->GetCompilerType();
chunk = m_first;
}
if (!type || !chunk)
- return ValueObjectSP();
+ return {};
- size_t chunk_idx = idx % type.GetBitSize(ctx.GetBestExecutionContextScope());
+ auto bit_size = type.GetBitSize(ctx.GetBestExecutionContextScope());
+ if (!bit_size || *bit_size == 0)
+ return {};
+ size_t chunk_idx = idx % *bit_size;
uint8_t value = !!(chunk->GetValueAsUnsigned(0) & (uint64_t(1) << chunk_idx));
DataExtractor data(&value, sizeof(value), m_byte_order, m_byte_size);