[Lldb-commits] [lldb] d72c8b0 - [lldb][TypeSystemClang] Create VLAs of explicitly 0-size as ConstantArrayType (#100710)
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lldb-commits at lists.llvm.org
Mon Jul 29 01:35:03 PDT 2024
Author: Michael Buch
Date: 2024-07-29T09:35:00+01:00
New Revision: d72c8b02802c87386f5db3c7de6c79e921618fa3
URL: https://github.com/llvm/llvm-project/commit/d72c8b02802c87386f5db3c7de6c79e921618fa3
DIFF: https://github.com/llvm/llvm-project/commit/d72c8b02802c87386f5db3c7de6c79e921618fa3.diff
LOG: [lldb][TypeSystemClang] Create VLAs of explicitly 0-size as ConstantArrayType (#100710)
Depends on https://github.com/llvm/llvm-project/pull/100674
Currently, we treat VLAs declared as `int[]` and `int[0]` identically.
I.e., we create them as `IncompleteArrayType`s. However, the
`DW_AT_count` for `int[0]` *does* exist, and is retrievable without an
execution context. This patch decouples the notion of "has 0 elements"
from "has no known `DW_AT_count`".
This aligns with how Clang represents `int[0]` in the AST (it treats it
as a `ConstantArrayType` of 0 size).
This issue was surfaced when adapting LLDB to
https://github.com/llvm/llvm-project/issues/93069. There, the
`__compressed_pair_padding` type has a `char[0]` member. If we
previously got the `__compressed_pair_padding` out of a module (where
clang represents `char[0]` as a `ConstantArrayType`), and try to merge
the AST with one we got from DWARF (where LLDB used to represent
`char[0]` as an `IncompleteArrayType`), the AST structural equivalence
check fails, resulting in silent ASTImporter failures. This manifested
in a failure in `TestNonModuleTypeSeparation.py`.
**Implementation**
1. Adjust `ParseChildArrayInfo` to store the element counts of each VLA
dimension as an `optional<uint64_t>`, instead of a regular `uint64_t`.
So when we pass this down to `CreateArrayType`, we have a better
heuristic for what is an `IncompleteArrayType`.
2. In `TypeSystemClang::GetBitSize`, if we encounter a
`ConstantArrayType` simply return the size that it was created with. If
we couldn't determine the authoritative bound from DWARF during parsing,
we would've created an `IncompleteArrayType`. This ensures that
`GetBitSize` on arrays with `DW_AT_count 0x0` returns `0` (whereas
previously it would've returned a `std::nullopt`, causing that
`FieldDecl` to just get dropped during printing)
Added:
lldb/test/Shell/SymbolFile/DWARF/vla.cpp
Modified:
lldb/include/lldb/Symbol/SymbolFile.h
lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.cpp
lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h
lldb/test/API/lang/c/struct_types/main.c
Removed:
################################################################################
diff --git a/lldb/include/lldb/Symbol/SymbolFile.h b/lldb/include/lldb/Symbol/SymbolFile.h
index d20766788192f..8419495da73a2 100644
--- a/lldb/include/lldb/Symbol/SymbolFile.h
+++ b/lldb/include/lldb/Symbol/SymbolFile.h
@@ -211,7 +211,15 @@ class SymbolFile : public PluginInterface {
/// The characteristics of an array type.
struct ArrayInfo {
int64_t first_index = 0;
- llvm::SmallVector<uint64_t, 1> element_orders;
+
+ ///< Each entry belongs to a distinct DW_TAG_subrange_type.
+ ///< For multi-dimensional DW_TAG_array_types we would have
+ ///< an entry for each dimension. An entry represents the
+ ///< optional element count of the subrange.
+ ///
+ ///< The order of entries follows the order of the DW_TAG_subrange_type
+ ///< children of this DW_TAG_array_type.
+ llvm::SmallVector<std::optional<uint64_t>, 1> element_orders;
uint32_t byte_stride = 0;
uint32_t bit_stride = 0;
};
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.cpp
index 409e9bb37ab28..4ed523bbb9e76 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParser.cpp
@@ -37,7 +37,7 @@ DWARFASTParser::ParseChildArrayInfo(const DWARFDIE &parent_die,
if (attributes.Size() == 0)
continue;
- uint64_t num_elements = 0;
+ std::optional<uint64_t> num_elements;
uint64_t lower_bound = 0;
uint64_t upper_bound = 0;
bool upper_bound_valid = false;
@@ -91,7 +91,7 @@ DWARFASTParser::ParseChildArrayInfo(const DWARFDIE &parent_die,
}
}
- if (num_elements == 0) {
+ if (!num_elements || *num_elements == 0) {
if (upper_bound_valid && upper_bound >= lower_bound)
num_elements = upper_bound - lower_bound + 1;
}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index 85c59a605c675..a4dcde1629fc2 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -1395,20 +1395,20 @@ DWARFASTParserClang::ParseArrayType(const DWARFDIE &die,
uint64_t array_element_bit_stride = byte_stride * 8 + bit_stride;
CompilerType clang_type;
if (array_info && array_info->element_orders.size() > 0) {
- uint64_t num_elements = 0;
auto end = array_info->element_orders.rend();
for (auto pos = array_info->element_orders.rbegin(); pos != end; ++pos) {
- num_elements = *pos;
- clang_type = m_ast.CreateArrayType(array_element_type, num_elements,
- attrs.is_vector);
+ clang_type = m_ast.CreateArrayType(
+ array_element_type, /*element_count=*/*pos, attrs.is_vector);
+
+ uint64_t num_elements = pos->value_or(0);
array_element_type = clang_type;
array_element_bit_stride = num_elements
? array_element_bit_stride * num_elements
: array_element_bit_stride;
}
} else {
- clang_type =
- m_ast.CreateArrayType(array_element_type, 0, attrs.is_vector);
+ clang_type = m_ast.CreateArrayType(
+ array_element_type, /*element_count=*/std::nullopt, attrs.is_vector);
}
ConstString empty_name;
TypeSP type_sp =
diff --git a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
index 0386e3b261c55..484ca04fe04c9 100644
--- a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
+++ b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
@@ -2233,30 +2233,31 @@ TypeSystemClang::CreateBlockPointerType(const CompilerType &function_type) {
#pragma mark Array Types
-CompilerType TypeSystemClang::CreateArrayType(const CompilerType &element_type,
- size_t element_count,
- bool is_vector) {
- if (element_type.IsValid()) {
- ASTContext &ast = getASTContext();
+CompilerType
+TypeSystemClang::CreateArrayType(const CompilerType &element_type,
+ std::optional<size_t> element_count,
+ bool is_vector) {
+ if (!element_type.IsValid())
+ return {};
- if (is_vector) {
- return GetType(ast.getExtVectorType(ClangUtil::GetQualType(element_type),
- element_count));
- } else {
+ ASTContext &ast = getASTContext();
- llvm::APInt ap_element_count(64, element_count);
- if (element_count == 0) {
- return GetType(
- ast.getIncompleteArrayType(ClangUtil::GetQualType(element_type),
- clang::ArraySizeModifier::Normal, 0));
- } else {
- return GetType(ast.getConstantArrayType(
- ClangUtil::GetQualType(element_type), ap_element_count, nullptr,
- clang::ArraySizeModifier::Normal, 0));
- }
- }
- }
- return CompilerType();
+ // Unknown number of elements; this is an incomplete array
+ // (e.g., variable length array with non-constant bounds, or
+ // a flexible array member).
+ if (!element_count)
+ return GetType(
+ ast.getIncompleteArrayType(ClangUtil::GetQualType(element_type),
+ clang::ArraySizeModifier::Normal, 0));
+
+ if (is_vector)
+ return GetType(ast.getExtVectorType(ClangUtil::GetQualType(element_type),
+ *element_count));
+
+ llvm::APInt ap_element_count(64, *element_count);
+ return GetType(ast.getConstantArrayType(ClangUtil::GetQualType(element_type),
+ ap_element_count, nullptr,
+ clang::ArraySizeModifier::Normal, 0));
}
CompilerType TypeSystemClang::CreateStructForIdentifier(
@@ -4767,6 +4768,7 @@ TypeSystemClang::GetBitSize(lldb::opaque_compiler_type_t type,
clang::QualType qual_type(GetCanonicalQualType(type));
const clang::Type::TypeClass type_class = qual_type->getTypeClass();
switch (type_class) {
+ case clang::Type::ConstantArray:
case clang::Type::FunctionProto:
case clang::Type::Record:
return getASTContext().getTypeSize(qual_type);
@@ -5457,9 +5459,9 @@ TypeSystemClang::GetNumChildren(lldb::opaque_compiler_type_t type,
case clang::Type::IncompleteArray:
if (auto array_info =
GetDynamicArrayInfo(*this, GetSymbolFile(), qual_type, exe_ctx))
- // Only 1-dimensional arrays are supported.
+ // FIXME: Only 1-dimensional arrays are supported.
num_children = array_info->element_orders.size()
- ? array_info->element_orders.back()
+ ? array_info->element_orders.back().value_or(0)
: 0;
break;
diff --git a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h
index 70722eb375ab7..56a5c0a516706 100644
--- a/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h
+++ b/lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.h
@@ -498,7 +498,8 @@ class TypeSystemClang : public TypeSystem {
// Array Types
CompilerType CreateArrayType(const CompilerType &element_type,
- size_t element_count, bool is_vector);
+ std::optional<size_t> element_count,
+ bool is_vector);
// Enumeration Types
CompilerType CreateEnumerationType(llvm::StringRef name,
diff --git a/lldb/test/API/lang/c/struct_types/main.c b/lldb/test/API/lang/c/struct_types/main.c
index e683c49108976..70217c57bec5f 100644
--- a/lldb/test/API/lang/c/struct_types/main.c
+++ b/lldb/test/API/lang/c/struct_types/main.c
@@ -1,3 +1,4 @@
+// clang-format off
struct things_to_sum {
int a;
int b;
@@ -18,7 +19,7 @@ int main (int argc, char const *argv[])
}; //% self.expect("frame variable pt.padding[0]", DATA_TYPES_DISPLAYED_CORRECTLY, substrs = ["pt.padding[0] = "])
//% self.expect("frame variable pt.padding[1]", DATA_TYPES_DISPLAYED_CORRECTLY, substrs = ["pt.padding[1] = "])
//% self.expect_expr("pt.padding[0]", result_type="char")
- //% self.expect("image lookup -t point_tag", DATA_TYPES_DISPLAYED_CORRECTLY, substrs = ['padding[]'])
+ //% self.expect("image lookup -t point_tag", DATA_TYPES_DISPLAYED_CORRECTLY, substrs = ['padding[0]'])
struct {} empty;
//% self.expect("frame variable empty", substrs = ["empty = {}"])
diff --git a/lldb/test/Shell/SymbolFile/DWARF/vla.cpp b/lldb/test/Shell/SymbolFile/DWARF/vla.cpp
new file mode 100644
index 0000000000000..344b100efd9f9
--- /dev/null
+++ b/lldb/test/Shell/SymbolFile/DWARF/vla.cpp
@@ -0,0 +1,80 @@
+// RUN: %clangxx_host -gdwarf -std=c++11 -o %t %s
+// RUN: %lldb %t \
+// RUN: -o run \
+// RUN: -o "frame var --show-types f" \
+// RUN: -o "frame var vla0" \
+// RUN: -o "frame var fla0" \
+// RUN: -o "frame var fla1" \
+// RUN: -o "frame var vla01" \
+// RUN: -o "frame var vla10" \
+// RUN: -o "frame var vlaN" \
+// RUN: -o "frame var vlaNM" \
+// RUN: -o exit | FileCheck %s
+
+struct Foo {
+ static constexpr int n = 1;
+ int m_vlaN[n];
+
+ int m_vla0[0];
+};
+
+int main() {
+ Foo f;
+ f.m_vlaN[0] = 60;
+
+ // CHECK: (lldb) frame var --show-types f
+ // CHECK-NEXT: (Foo) f = {
+ // CHECK-NEXT: (int[1]) m_vlaN = {
+ // CHECK-NEXT: (int) [0] = 60
+ // CHECK-NEXT: }
+ // CHECK-NEXT: (int[0]) m_vla0 = {}
+ // CHECK-NEXT: }
+
+ int vla0[0] = {};
+
+ // CHECK: (lldb) frame var vla0
+ // CHECK-NEXT: (int[0]) vla0 = {}
+
+ int fla0[] = {};
+
+ // CHECK: (lldb) frame var fla0
+ // CHECK-NEXT: (int[0]) fla0 = {}
+
+ int fla1[] = {42};
+
+ // CHECK: (lldb) frame var fla1
+ // CHECK-NEXT: (int[1]) fla1 = ([0] = 42)
+
+ int vla01[0][1];
+
+ // CHECK: (lldb) frame var vla01
+ // CHECK-NEXT: (int[0][1]) vla01 = {}
+
+ int vla10[1][0];
+
+ // CHECK: (lldb) frame var vla10
+ // CHECK-NEXT: (int[1][0]) vla10 = ([0] = int[0]
+
+ int n = 3;
+ int vlaN[n];
+ for (int i = 0; i < n; ++i)
+ vlaN[i] = -i;
+
+ // CHECK: (lldb) frame var vlaN
+ // CHECK-NEXT: (int[]) vlaN = ([0] = 0, [1] = -1, [2] = -2)
+
+ int m = 2;
+ int vlaNM[n][m];
+ for (int i = 0; i < n; ++i)
+ for (int j = 0; j < m; ++j)
+ vlaNM[i][j] = i + j;
+
+ // FIXME: multi-dimensional VLAs aren't well supported
+ // CHECK: (lldb) frame var vlaNM
+ // CHECK-NEXT: (int[][]) vlaNM = {
+ // CHECK-NEXT: [0] = ([0] = 0, [1] = 1, [2] = 1)
+ // CHECK-NEXT: [1] = ([0] = 1, [1] = 1, [2] = 2)
+ // CHECK-NEXT: }
+
+ __builtin_debugtrap();
+}
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