[Lldb-commits] [lldb] fcaf5f6 - [LLDB] Fix the handling of unnamed bit-fields when parsing DWARF
Hans Wennborg via lldb-commits
lldb-commits at lists.llvm.org
Mon Jan 27 06:10:46 PST 2020
Sure, b5cf892651812003e64c4a8f0dbf81f74a499016
On Mon, Jan 27, 2020 at 12:18 AM Raphael Isemann <risemann at apple.com> wrote:
>
> This commit fixes a *very* frequent crash when debugging Clang with LLDB 10. Could we get that cherry-picked into the 10.x branch?
>
> I’ve been running the patch since more than a week and I haven’t found any issues with it and the bots are also happy.
>
> Thanks!
> - Raphael
>
> > On 23. Jan 2020, at 23:46, via lldb-commits <lldb-commits at lists.llvm.org> wrote:
> >
> >
> > Author: shafik
> > Date: 2020-01-23T14:46:24-08:00
> > New Revision: fcaf5f6c01a09f23b948afb8c91c4dd951d4525e
> >
> > URL: https://github.com/llvm/llvm-project/commit/fcaf5f6c01a09f23b948afb8c91c4dd951d4525e
> > DIFF: https://github.com/llvm/llvm-project/commit/fcaf5f6c01a09f23b948afb8c91c4dd951d4525e.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
> >
> > 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 1aa82ab67ce6..7a610e042b48 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 =
> > TypeSystemClang::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();
> > TypeSystemClang *ast =
> >
> > diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h
> > index 299281876d6c..6cd2dc8bf558 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);
> >
> >
> >
> > _______________________________________________
> > lldb-commits mailing list
> > lldb-commits at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
>
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