[llvm-branch-commits] [lldb] b5cf892 - [LLDB] Fix the handling of unnamed bit-fields when parsing DWARF
Hans Wennborg via llvm-branch-commits
llvm-branch-commits at lists.llvm.org
Mon Jan 27 06:10:28 PST 2020
Author: shafik
Date: 2020-01-27T15:10:11+01:00
New Revision: b5cf892651812003e64c4a8f0dbf81f74a499016
URL: https://github.com/llvm/llvm-project/commit/b5cf892651812003e64c4a8f0dbf81f74a499016
DIFF: https://github.com/llvm/llvm-project/commit/b5cf892651812003e64c4a8f0dbf81f74a499016.diff
LOG: [LLDB] Fix the handling of unnamed bit-fields when parsing DWARF
We ran into an assert when debugging clang and performing an expression on a class derived from DeclContext. The assert was indicating we were getting the offsets wrong for RecordDeclBitfields. We were getting both the size and offset of unnamed bit-field members wrong. We could fix this case with a quick change but as I extended the test suite to include more combinations we kept finding more cases that were being handled incorrectly. A fix that handled all the new cases as well as the cases already covered required a refactor of the existing technique.
Differential Revision: https://reviews.llvm.org/D72953
(cherry picked from commit fcaf5f6c01a09f23b948afb8c91c4dd951d4525e)
Added:
lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/Makefile
lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/TestCppBitfields.py
lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/main.cpp
Modified:
lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
Removed:
################################################################################
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/Makefile b/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/Makefile
new file mode 100644
index 000000000000..99998b20bcb0
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/Makefile
@@ -0,0 +1,3 @@
+CXX_SOURCES := main.cpp
+
+include Makefile.rules
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/TestCppBitfields.py b/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/TestCppBitfields.py
new file mode 100644
index 000000000000..696e5647f13f
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/TestCppBitfields.py
@@ -0,0 +1,105 @@
+"""Show bitfields and check that they display correctly."""
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test import lldbutil
+
+
+class CppBitfieldsTestCase(TestBase):
+
+ mydir = TestBase.compute_mydir(__file__)
+
+ def setUp(self):
+ # Call super's setUp().
+ TestBase.setUp(self)
+ # Find the line number to break inside main().
+ self.line = line_number('main.cpp', '// Set break point at this line.')
+
+ # BitFields exhibit crashes in record layout on Windows
+ # (http://llvm.org/pr21800)
+ @skipIfWindows
+ def test_and_run_command(self):
+ """Test 'frame variable ...' on a variable with bitfields."""
+ self.build()
+
+ lldbutil.run_to_source_breakpoint(self, '// Set break point at this line.',
+ lldb.SBFileSpec("main.cpp", False))
+
+ # The stop reason of the thread should be breakpoint.
+ self.expect("thread list", STOPPED_DUE_TO_BREAKPOINT,
+ substrs=['stopped',
+ 'stop reason = breakpoint'])
+
+ # The breakpoint should have a hit count of 1.
+ self.expect("breakpoint list -f", BREAKPOINT_HIT_ONCE,
+ substrs=[' resolved, hit count = 1'])
+
+ self.expect("expr (lba.a)", VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=['unsigned int', '2'])
+ self.expect("expr (lbb.b)", VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=['unsigned int', '3'])
+ self.expect("expr (lbc.c)", VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=['unsigned int', '4'])
+ self.expect("expr (lbd.a)", VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=['unsigned int', '5'])
+ self.expect("expr (clang_example.f.a)", VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=['uint64_t', '1'])
+
+ self.expect(
+ "frame variable --show-types lba",
+ VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=[
+ '(int:32) = ',
+ '(unsigned int:20) a = 2',
+ ])
+
+ self.expect(
+ "frame variable --show-types lbb",
+ VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=[
+ '(unsigned int:1) a = 1',
+ '(int:31) =',
+ '(unsigned int:20) b = 3',
+ ])
+
+ self.expect(
+ "frame variable --show-types lbc",
+ VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=[
+ '(int:22) =',
+ '(unsigned int:1) a = 1',
+ '(unsigned int:1) b = 0',
+ '(unsigned int:5) c = 4',
+ '(unsigned int:1) d = 1',
+ '(int:2) =',
+ '(unsigned int:20) e = 20',
+ ])
+
+ self.expect(
+ "frame variable --show-types lbd",
+ VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=[
+ '(char [3]) arr = "abc"',
+ '(int:32) =',
+ '(unsigned int:20) a = 5',
+ ])
+
+ self.expect(
+ "frame variable --show-types clang_example",
+ VARIABLES_DISPLAYED_CORRECTLY,
+ substrs=[
+ '(int:22) =',
+ '(uint64_t:1) a = 1',
+ '(uint64_t:1) b = 0',
+ '(uint64_t:1) c = 1',
+ '(uint64_t:1) d = 0',
+ '(uint64_t:1) e = 1',
+ '(uint64_t:1) f = 0',
+ '(uint64_t:1) g = 1',
+ '(uint64_t:1) h = 0',
+ '(uint64_t:1) i = 1',
+ '(uint64_t:1) j = 0',
+ '(uint64_t:1) k = 1',
+ ])
+
diff --git a/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/main.cpp b/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/main.cpp
new file mode 100644
index 000000000000..975c0f05683c
--- /dev/null
+++ b/lldb/packages/Python/lldbsuite/test/lang/cpp/bitfields/main.cpp
@@ -0,0 +1,81 @@
+#include <stdint.h>
+
+int main(int argc, char const *argv[]) {
+ struct LargeBitsA {
+ unsigned int : 30, a : 20;
+ } lba;
+
+ struct LargeBitsB {
+ unsigned int a : 1, : 11, : 12, b : 20;
+ } lbb;
+
+ struct LargeBitsC {
+ unsigned int : 13, : 9, a : 1, b : 1, c : 5, d : 1, e : 20;
+ } lbc;
+
+ struct LargeBitsD {
+ char arr[3];
+ unsigned int : 30, a : 20;
+ } lbd;
+
+ // This case came up when debugging clang and models RecordDeclBits
+ struct BitExampleFromClangDeclContext {
+ class fields {
+ uint64_t : 13;
+ uint64_t : 9;
+
+ uint64_t a: 1;
+ uint64_t b: 1;
+ uint64_t c: 1;
+ uint64_t d: 1;
+ uint64_t e: 1;
+ uint64_t f: 1;
+ uint64_t g: 1;
+ uint64_t h: 1;
+ uint64_t i: 1;
+ uint64_t j: 1;
+ uint64_t k: 1;
+
+ // In order to reproduce the crash for this case we need the
+ // members of fields to stay private :-(
+ friend struct BitExampleFromClangDeclContext;
+ };
+
+ union {
+ struct fields f;
+ };
+
+ BitExampleFromClangDeclContext() {
+ f.a = 1;
+ f.b = 0;
+ f.c = 1;
+ f.d = 0;
+ f.e = 1;
+ f.f = 0;
+ f.g = 1;
+ f.h = 0;
+ f.i = 1;
+ f.j = 0;
+ f.k = 1;
+ }
+ } clang_example;
+
+ lba.a = 2;
+
+ lbb.a = 1;
+ lbb.b = 3;
+
+ lbc.a = 1;
+ lbc.b = 0;
+ lbc.c = 4;
+ lbc.d = 1;
+ lbc.e = 20;
+
+ lbd.arr[0] = 'a';
+ lbd.arr[1] = 'b';
+ lbd.arr[2] = 'c';
+ lbd.a = 5;
+
+
+ return 0; // Set break point at this line.
+}
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index 232063a6f339..6166aa77bda4 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -85,35 +85,6 @@ static bool DeclKindIsCXXClass(clang::Decl::Kind decl_kind) {
return false;
}
-struct BitfieldInfo {
- uint64_t bit_size;
- uint64_t bit_offset;
-
- BitfieldInfo()
- : bit_size(LLDB_INVALID_ADDRESS), bit_offset(LLDB_INVALID_ADDRESS) {}
-
- void Clear() {
- bit_size = LLDB_INVALID_ADDRESS;
- bit_offset = LLDB_INVALID_ADDRESS;
- }
-
- bool IsValid() const {
- return (bit_size != LLDB_INVALID_ADDRESS) &&
- (bit_offset != LLDB_INVALID_ADDRESS);
- }
-
- bool NextBitfieldOffsetIsValid(const uint64_t next_bit_offset) const {
- if (IsValid()) {
- // This bitfield info is valid, so any subsequent bitfields must not
- // overlap and must be at a higher bit offset than any previous bitfield
- // + size.
- return (bit_size + bit_offset) <= next_bit_offset;
- } else {
- // If the this BitfieldInfo is not valid, then any offset isOK
- return true;
- }
- }
-};
ClangASTImporter &DWARFASTParserClang::GetClangASTImporter() {
if (!m_clang_ast_importer_up) {
@@ -2419,7 +2390,7 @@ void DWARFASTParserClang::ParseSingleMember(
lldb::AccessType &default_accessibility,
DelayedPropertyList &delayed_properties,
lldb_private::ClangASTImporter::LayoutInfo &layout_info,
- BitfieldInfo &last_field_info) {
+ FieldInfo &last_field_info) {
ModuleSP module_sp = parent_die.GetDWARF()->GetObjectFile()->GetModule();
const dw_tag_t tag = die.Tag();
// Get the parent byte size so we can verify any members will fit
@@ -2453,6 +2424,14 @@ void DWARFASTParserClang::ParseSingleMember(
const dw_attr_t attr = attributes.AttributeAtIndex(i);
DWARFFormValue form_value;
if (attributes.ExtractFormValueAtIndex(i, form_value)) {
+ // DW_AT_data_member_location indicates the byte offset of the
+ // word from the base address of the structure.
+ //
+ // DW_AT_bit_offset indicates how many bits into the word
+ // (according to the host endianness) the low-order bit of the
+ // field starts. AT_bit_offset can be negative.
+ //
+ // DW_AT_bit_size indicates the size of the field in bits.
switch (attr) {
case DW_AT_name:
name = form_value.AsCString();
@@ -2603,36 +2582,24 @@ void DWARFASTParserClang::ParseSingleMember(
Type *member_type = die.ResolveTypeUID(encoding_form.Reference());
clang::FieldDecl *field_decl = nullptr;
+ const uint64_t character_width = 8;
+ const uint64_t word_width = 32;
if (tag == DW_TAG_member) {
if (member_type) {
+ CompilerType member_clang_type = member_type->GetLayoutCompilerType();
+
if (accessibility == eAccessNone)
accessibility = default_accessibility;
member_accessibilities.push_back(accessibility);
uint64_t field_bit_offset =
(member_byte_offset == UINT32_MAX ? 0 : (member_byte_offset * 8));
- if (bit_size > 0) {
- BitfieldInfo this_field_info;
+ if (bit_size > 0) {
+ FieldInfo this_field_info;
this_field_info.bit_offset = field_bit_offset;
this_field_info.bit_size = bit_size;
- /////////////////////////////////////////////////////////////
- // How to locate a field given the DWARF debug information
- //
- // AT_byte_size indicates the size of the word in which the bit
- // offset must be interpreted.
- //
- // AT_data_member_location indicates the byte offset of the
- // word from the base address of the structure.
- //
- // AT_bit_offset indicates how many bits into the word
- // (according to the host endianness) the low-order bit of the
- // field starts. AT_bit_offset can be negative.
- //
- // AT_bit_size indicates the size of the field in bits.
- /////////////////////////////////////////////////////////////
-
if (data_bit_offset != UINT64_MAX) {
this_field_info.bit_offset = data_bit_offset;
} else {
@@ -2649,8 +2616,9 @@ void DWARFASTParserClang::ParseSingleMember(
}
if ((this_field_info.bit_offset >= parent_bit_size) ||
- !last_field_info.NextBitfieldOffsetIsValid(
- this_field_info.bit_offset)) {
+ (last_field_info.IsBitfield() &&
+ !last_field_info.NextBitfieldOffsetIsValid(
+ this_field_info.bit_offset))) {
ObjectFile *objfile = die.GetDWARF()->GetObjectFile();
objfile->GetModule()->ReportWarning(
"0x%8.8" PRIx64 ": %s bitfield named \"%s\" has invalid "
@@ -2659,40 +2627,12 @@ void DWARFASTParserClang::ParseSingleMember(
"compiler and include the preprocessed output for %s\n",
die.GetID(), DW_TAG_value_to_name(tag), name,
this_field_info.bit_offset, GetUnitName(parent_die).c_str());
- this_field_info.Clear();
return;
}
// Update the field bit offset we will report for layout
field_bit_offset = this_field_info.bit_offset;
- // If the member to be emitted did not start on a character
- // boundary and there is empty space between the last field and
- // this one, then we need to emit an anonymous member filling
- // up the space up to its start. There are three cases here:
- //
- // 1 If the previous member ended on a character boundary, then
- // we can emit an
- // anonymous member starting at the most recent character
- // boundary.
- //
- // 2 If the previous member did not end on a character boundary
- // and the distance
- // from the end of the previous member to the current member
- // is less than a
- // word width, then we can emit an anonymous member starting
- // right after the
- // previous member and right before this member.
- //
- // 3 If the previous member did not end on a character boundary
- // and the distance
- // from the end of the previous member to the current member
- // is greater than
- // or equal a word width, then we act as in Case 1.
-
- const uint64_t character_width = 8;
- const uint64_t word_width = 32;
-
// Objective-C has invalid DW_AT_bit_offset values in older
// versions of clang, so we have to be careful and only insert
// unnamed bitfields if we have a new enough clang.
@@ -2704,53 +2644,57 @@ void DWARFASTParserClang::ParseSingleMember(
die.GetCU()->Supports_unnamed_objc_bitfields();
if (detect_unnamed_bitfields) {
- BitfieldInfo anon_field_info;
-
- if ((this_field_info.bit_offset % character_width) !=
- 0) // not char aligned
- {
- uint64_t last_field_end = 0;
-
- if (last_field_info.IsValid())
- last_field_end =
- last_field_info.bit_offset + last_field_info.bit_size;
-
- if (this_field_info.bit_offset != last_field_end) {
- if (((last_field_end % character_width) == 0) || // case 1
- (this_field_info.bit_offset - last_field_end >=
- word_width)) // case 3
- {
- anon_field_info.bit_size =
- this_field_info.bit_offset % character_width;
- anon_field_info.bit_offset =
- this_field_info.bit_offset - anon_field_info.bit_size;
- } else // case 2
- {
- anon_field_info.bit_size =
- this_field_info.bit_offset - last_field_end;
- anon_field_info.bit_offset = last_field_end;
- }
- }
+ clang::Optional<FieldInfo> unnamed_field_info;
+ uint64_t last_field_end = 0;
+
+ last_field_end =
+ last_field_info.bit_offset + last_field_info.bit_size;
+
+ if (!last_field_info.IsBitfield()) {
+ // The last field was not a bit-field...
+ // but if it did take up the entire word then we need to extend
+ // last_field_end so the bit-field does not step into the last
+ // fields padding.
+ if (last_field_end != 0 && ((last_field_end % word_width) != 0))
+ last_field_end += word_width - (last_field_end % word_width);
}
- if (anon_field_info.IsValid()) {
+ // If we have a gap between the last_field_end and the current
+ // field we have an unnamed bit-field
+ if (this_field_info.bit_offset != last_field_end &&
+ !(this_field_info.bit_offset < last_field_end)) {
+ unnamed_field_info = FieldInfo{};
+ unnamed_field_info->bit_size =
+ this_field_info.bit_offset - last_field_end;
+ unnamed_field_info->bit_offset = last_field_end;
+ }
+
+ if (unnamed_field_info) {
clang::FieldDecl *unnamed_bitfield_decl =
ClangASTContext::AddFieldToRecordType(
class_clang_type, llvm::StringRef(),
m_ast.GetBuiltinTypeForEncodingAndBitSize(eEncodingSint,
word_width),
- accessibility, anon_field_info.bit_size);
+ accessibility, unnamed_field_info->bit_size);
layout_info.field_offsets.insert(std::make_pair(
- unnamed_bitfield_decl, anon_field_info.bit_offset));
+ unnamed_bitfield_decl, unnamed_field_info->bit_offset));
}
}
+
last_field_info = this_field_info;
+ last_field_info.SetIsBitfield(true);
} else {
- last_field_info.Clear();
+ last_field_info.bit_offset = field_bit_offset;
+
+ if (llvm::Optional<uint64_t> clang_type_size =
+ member_clang_type.GetByteSize(nullptr)) {
+ last_field_info.bit_size = *clang_type_size * character_width;
+ }
+
+ last_field_info.SetIsBitfield(false);
}
- CompilerType member_clang_type = member_type->GetLayoutCompilerType();
if (!member_clang_type.IsCompleteType())
member_clang_type.GetCompleteType();
@@ -2885,7 +2829,7 @@ bool DWARFASTParserClang::ParseChildMembers(
if (!parent_die)
return false;
- BitfieldInfo last_field_info;
+ FieldInfo last_field_info;
ModuleSP module_sp = parent_die.GetDWARF()->GetObjectFile()->GetModule();
ClangASTContext *ast =
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
index 4ad757247c3e..8a78299c8b10 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
@@ -170,33 +170,20 @@ class DWARFASTParserClang : public DWARFASTParser {
lldb::ModuleSP GetModuleForType(const DWARFDIE &die);
private:
- struct BitfieldInfo {
- uint64_t bit_size;
- uint64_t bit_offset;
+ struct FieldInfo {
+ uint64_t bit_size = 0;
+ uint64_t bit_offset = 0;
+ bool is_bitfield = false;
- BitfieldInfo()
- : bit_size(LLDB_INVALID_ADDRESS), bit_offset(LLDB_INVALID_ADDRESS) {}
+ FieldInfo() = default;
- void Clear() {
- bit_size = LLDB_INVALID_ADDRESS;
- bit_offset = LLDB_INVALID_ADDRESS;
- }
-
- bool IsValid() const {
- return (bit_size != LLDB_INVALID_ADDRESS) &&
- (bit_offset != LLDB_INVALID_ADDRESS);
- }
+ void SetIsBitfield(bool flag) { is_bitfield = flag; }
+ bool IsBitfield() { return is_bitfield; }
bool NextBitfieldOffsetIsValid(const uint64_t next_bit_offset) const {
- if (IsValid()) {
- // This bitfield info is valid, so any subsequent bitfields must not
- // overlap and must be at a higher bit offset than any previous bitfield
- // + size.
- return (bit_size + bit_offset) <= next_bit_offset;
- } else {
- // If the this BitfieldInfo is not valid, then any offset isOK
- return true;
- }
+ // Any subsequent bitfields must not overlap and must be at a higher
+ // bit offset than any previous bitfield + size.
+ return (bit_size + bit_offset) <= next_bit_offset;
}
};
@@ -208,7 +195,7 @@ class DWARFASTParserClang : public DWARFASTParser {
lldb::AccessType &default_accessibility,
DelayedPropertyList &delayed_properties,
lldb_private::ClangASTImporter::LayoutInfo &layout_info,
- BitfieldInfo &last_field_info);
+ FieldInfo &last_field_info);
bool CompleteRecordType(const DWARFDIE &die, lldb_private::Type *type,
lldb_private::CompilerType &clang_type);
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