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

6 files changed, 86 insertions, 51 deletions

diff --git a/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp b/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp
index 0f6fb54e838..6a41ff84e0b 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/CxxStringTypes.cpp
@@ -100,8 +100,11 @@ bool lldb_private::formatters::WCharStringSummaryProvider(
   if (!wchar_compiler_type)
     return false;
 
-  const uint32_t wchar_size = wchar_compiler_type.GetBitSize(
-      nullptr); // Safe to pass NULL for exe_scope here
+  // Safe to pass nullptr for exe_scope here.
+  auto size = wchar_compiler_type.GetBitSize(nullptr);
+  if (!size)
+    return false;
+  const uint32_t wchar_size = *size;
 
   StringPrinter::ReadStringAndDumpToStreamOptions options(valobj);
   options.SetLocation(valobj_addr);
@@ -194,8 +197,11 @@ bool lldb_private::formatters::WCharSummaryProvider(
   if (!wchar_compiler_type)
     return false;
 
-  const uint32_t wchar_size = wchar_compiler_type.GetBitSize(
-      nullptr); // Safe to pass NULL for exe_scope here
+    // Safe to pass nullptr for exe_scope here.
+  auto size = wchar_compiler_type.GetBitSize(nullptr);
+  if (!size)
+    return false;
+  const uint32_t wchar_size = *size;
 
   StringPrinter::ReadBufferAndDumpToStreamOptions options(valobj);
   options.SetData(data);
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
index 5a560683f0e..af118a71d09 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxx.cpp
@@ -225,9 +225,14 @@ bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::Update() {
         m_pair_ptr = nullptr;
         return false;
       }
-      CompilerType pair_type(__i_->GetCompilerType().GetTypeTemplateArgument(0));
-      std::string name; uint64_t bit_offset_ptr; uint32_t bitfield_bit_size_ptr; bool is_bitfield_ptr;
-      pair_type = pair_type.GetFieldAtIndex(0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
+      CompilerType pair_type(
+          __i_->GetCompilerType().GetTypeTemplateArgument(0));
+      std::string name;
+      uint64_t bit_offset_ptr;
+      uint32_t bitfield_bit_size_ptr;
+      bool is_bitfield_ptr;
+      pair_type = pair_type.GetFieldAtIndex(
+          0, name, &bit_offset_ptr, &bitfield_bit_size_ptr, &is_bitfield_ptr);
       if (!pair_type) {
         m_pair_ptr = nullptr;
         return false;
@@ -235,27 +240,38 @@ bool lldb_private::formatters::LibCxxMapIteratorSyntheticFrontEnd::Update() {
 
       auto addr(m_pair_ptr->GetValueAsUnsigned(LLDB_INVALID_ADDRESS));
       m_pair_ptr = nullptr;
-      if (addr && addr!=LLDB_INVALID_ADDRESS) {
-        ClangASTContext *ast_ctx = llvm::dyn_cast_or_null<ClangASTContext>(pair_type.GetTypeSystem());
+      if (addr && addr != LLDB_INVALID_ADDRESS) {
+        ClangASTContext *ast_ctx =
+            llvm::dyn_cast_or_null<ClangASTContext>(pair_type.GetTypeSystem());
         if (!ast_ctx)
           return false;
-        CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(ConstString(), {
-          {"ptr0",ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-          {"ptr1",ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-          {"ptr2",ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
-          {"cw",ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
-          {"payload",pair_type}
-        });
-        DataBufferSP buffer_sp(new DataBufferHeap(tree_node_type.GetByteSize(nullptr),0));
+        CompilerType tree_node_type = ast_ctx->CreateStructForIdentifier(
+            ConstString(),
+            {{"ptr0",
+              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
+             {"ptr1",
+              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
+             {"ptr2",
+              ast_ctx->GetBasicType(lldb::eBasicTypeVoid).GetPointerType()},
+             {"cw", ast_ctx->GetBasicType(lldb::eBasicTypeBool)},
+             {"payload", pair_type}});
+        auto size = tree_node_type.GetByteSize(nullptr);
+        if (!size)
+          return false;
+        DataBufferSP buffer_sp(new DataBufferHeap(*size, 0));
         ProcessSP process_sp(target_sp->GetProcessSP());
         Status error;
-        process_sp->ReadMemory(addr, buffer_sp->GetBytes(), buffer_sp->GetByteSize(), error);
+        process_sp->ReadMemory(addr, buffer_sp->GetBytes(),
+                               buffer_sp->GetByteSize(), error);
         if (error.Fail())
           return false;
-        DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(), process_sp->GetAddressByteSize());
-        auto pair_sp = CreateValueObjectFromData("pair", extractor, valobj_sp->GetExecutionContextRef(), tree_node_type);
+        DataExtractor extractor(buffer_sp, process_sp->GetByteOrder(),
+                                process_sp->GetAddressByteSize());
+        auto pair_sp = CreateValueObjectFromData(
+            "pair", extractor, valobj_sp->GetExecutionContextRef(),
+            tree_node_type);
         if (pair_sp)
-          m_pair_sp = pair_sp->GetChildAtIndex(4,true);
+          m_pair_sp = pair_sp->GetChildAtIndex(4, true);
       }
     }
   }
@@ -560,6 +576,8 @@ bool lldb_private::formatters::LibcxxWStringSummaryProvider(
                           ->GetScratchClangASTContext()
                           ->GetBasicType(lldb::eBasicTypeWChar)
                           .GetByteSize(nullptr);
+  if (!wchar_t_size)
+    return false;
 
   options.SetData(extractor);
   options.SetStream(&stream);
@@ -568,7 +586,7 @@ bool lldb_private::formatters::LibcxxWStringSummaryProvider(
   options.SetSourceSize(size);
   options.SetBinaryZeroIsTerminator(false);
 
-  switch (wchar_t_size) {
+  switch (*wchar_t_size) {
   case 1:
     StringPrinter::ReadBufferAndDumpToStream<
         lldb_private::formatters::StringPrinter::StringElementType::UTF8>(
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp
index 0cdb0b26cf3..0d39e5a57cf 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxBitset.cpp
@@ -79,17 +79,22 @@ ValueObjectSP BitsetFrontEnd::GetChildAtIndex(size_t idx) {
   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);
 
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxInitializerList.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxInitializerList.cpp
index b000410aef8..a692c120b35 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxxInitializerList.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxInitializerList.cpp
@@ -94,12 +94,11 @@ bool lldb_private::formatters::LibcxxInitializerListSyntheticFrontEnd::
   if (!m_element_type.IsValid())
     return false;
 
-  m_element_size = m_element_type.GetByteSize(nullptr);
-
-  if (m_element_size > 0)
-    m_start =
-        m_backend.GetChildMemberWithName(g___begin_, true)
-            .get(); // store raw pointers or end up with a circular dependency
+  if (auto size = m_element_type.GetByteSize(nullptr)) {
+    m_element_size = *size;
+    // Store raw pointers or end up with a circular dependency.
+    m_start = m_backend.GetChildMemberWithName(g___begin_, true).get();
+  }
 
   return false;
 }
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp
index c05e84fa0d3..9cde54b4f4f 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibCxxVector.cpp
@@ -145,14 +145,16 @@ bool lldb_private::formatters::LibcxxStdVectorSyntheticFrontEnd::Update() {
   if (!data_type_finder_sp)
     return false;
   m_element_type = data_type_finder_sp->GetCompilerType().GetPointeeType();
-  m_element_size = m_element_type.GetByteSize(nullptr);
-
-  if (m_element_size > 0) {
-    // store raw pointers or end up with a circular dependency
-    m_start =
-        m_backend.GetChildMemberWithName(ConstString("__begin_"), true).get();
-    m_finish =
-        m_backend.GetChildMemberWithName(ConstString("__end_"), true).get();
+  if (auto size = m_element_type.GetByteSize(nullptr)) {
+    m_element_size = *size;
+
+    if (m_element_size > 0) {
+      // store raw pointers or end up with a circular dependency
+      m_start =
+          m_backend.GetChildMemberWithName(ConstString("__begin_"), true).get();
+      m_finish =
+          m_backend.GetChildMemberWithName(ConstString("__end_"), true).get();
+    }
   }
   return false;
 }
@@ -192,27 +194,29 @@ lldb_private::formatters::LibcxxVectorBoolSyntheticFrontEnd::GetChildAtIndex(
   if (iter != end)
     return iter->second;
   if (idx >= m_count)
-    return ValueObjectSP();
+    return {};
   if (m_base_data_address == 0 || m_count == 0)
-    return ValueObjectSP();
+    return {};
   if (!m_bool_type)
-    return ValueObjectSP();
+    return {};
   size_t byte_idx = (idx >> 3); // divide by 8 to get byte index
   size_t bit_index = (idx & 7); // efficient idx % 8 for bit index
   lldb::addr_t byte_location = m_base_data_address + byte_idx;
   ProcessSP process_sp(m_exe_ctx_ref.GetProcessSP());
   if (!process_sp)
-    return ValueObjectSP();
+    return {};
   uint8_t byte = 0;
   uint8_t mask = 0;
   Status err;
   size_t bytes_read = process_sp->ReadMemory(byte_location, &byte, 1, err);
   if (err.Fail() || bytes_read == 0)
-    return ValueObjectSP();
+    return {};
   mask = 1 << bit_index;
   bool bit_set = ((byte & mask) != 0);
-  DataBufferSP buffer_sp(
-      new DataBufferHeap(m_bool_type.GetByteSize(nullptr), 0));
+  auto size = m_bool_type.GetByteSize(nullptr);
+  if (!size)
+    return {};
+  DataBufferSP buffer_sp(new DataBufferHeap(*size, 0));
   if (bit_set && buffer_sp && buffer_sp->GetBytes()) {
     // regardless of endianness, anything non-zero is true
     *(buffer_sp->GetBytes()) = 1;
diff --git a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
index 2827feb9741..f25391f9512 100644
--- a/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
+++ b/lldb/source/Plugins/Language/CPlusPlus/LibStdcpp.cpp
@@ -297,8 +297,11 @@ bool lldb_private::formatters::LibStdcppWStringSummaryProvider(
       if (!wchar_compiler_type)
         return false;
 
-      const uint32_t wchar_size = wchar_compiler_type.GetBitSize(
-          nullptr); // Safe to pass NULL for exe_scope here
+      // Safe to pass nullptr for exe_scope here.
+      auto size = wchar_compiler_type.GetBitSize(nullptr);
+      if (!size)
+        return false;
+      const uint32_t wchar_size = *size;
 
       StringPrinter::ReadStringAndDumpToStreamOptions options(valobj);
       Status error;