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[lldb] Fix member access in GetExpressionPath 

This change fixes two issues in ValueObject::GetExpressionPath method:

 1. Accessing members of struct references used to produce expression
    paths such as "str.&str.member" (instead of the expected
    "str.member"). This is fixed by assigning the flag tha the child
    value is a dereference when calling Dereference() on references
    and adjusting logic in expression path creation.

 2. If the parent of member access is dereference, the produced
    expression path was "*(ptr).member". This is incorrect, since it
    dereferences the member instead of the pointer. This is fixed by
    wrapping dereference expression into parenthesis, resulting with
    "(*ptr).member".

Reviewed By: werat, clayborg

Differential Revision: https://reviews.llvm.org/D132734
This commit is contained in:
Tonko Sabolčec 2022-10-12 11:46:23 +00:00 committed by Andy Yankovsky
parent b781ef890f
commit 0205aa4a02
6 changed files with 243 additions and 56 deletions
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137
lldb/source/Core/ValueObject.cpp
View File

@ -273,8 +273,6 @@ CompilerType ValueObject::MaybeCalculateCompleteType() {
return compiler_type;
}
DataExtractor &ValueObject::GetDataExtractor() {
UpdateValueIfNeeded(false);
return m_data;
@ -409,8 +407,9 @@ ValueObject::GetChildAtIndexPath(llvm::ArrayRef<size_t> idxs,
return root;
}
lldb::ValueObjectSP ValueObject::GetChildAtIndexPath(
llvm::ArrayRef<std::pair<size_t, bool>> idxs, size_t *index_of_error) {
lldb::ValueObjectSP
ValueObject::GetChildAtIndexPath(llvm::ArrayRef<std::pair<size_t, bool>> idxs,
size_t *index_of_error) {
if (idxs.size() == 0)
return GetSP();
ValueObjectSP root(GetSP());
@ -1185,9 +1184,10 @@ bool ValueObject::DumpPrintableRepresentation(
{
Status error;
lldb::WritableDataBufferSP buffer_sp;
std::pair<size_t, bool> read_string = ReadPointedString(
buffer_sp, error, 0, (custom_format == eFormatVectorOfChar) ||
(custom_format == eFormatCharArray));
std::pair<size_t, bool> read_string =
ReadPointedString(buffer_sp, error, 0,
(custom_format == eFormatVectorOfChar) ||
(custom_format == eFormatCharArray));
lldb_private::formatters::StringPrinter::
ReadBufferAndDumpToStreamOptions options(*this);
options.SetData(DataExtractor(
@ -1552,8 +1552,7 @@ bool ValueObject::GetDeclaration(Declaration &decl) {
return false;
}
void ValueObject::AddSyntheticChild(ConstString key,
ValueObject *valobj) {
void ValueObject::AddSyntheticChild(ConstString key, ValueObject *valobj) {
m_synthetic_children[key] = valobj;
}
@ -1924,64 +1923,96 @@ void ValueObject::GetExpressionPath(Stream &s,
return;
}
const bool is_deref_of_parent = IsDereferenceOfParent();
// Checks whether a value is dereference of a non-reference parent.
// This is used to determine whether to print a dereference operation (*).
auto is_deref_of_non_reference = [](ValueObject *value) {
if (value == nullptr)
return false;
ValueObject *value_parent = value->GetParent();
if (value_parent) {
CompilerType parent_compiler_type = value_parent->GetCompilerType();
if (parent_compiler_type) {
const uint32_t parent_type_info = parent_compiler_type.GetTypeInfo();
if (parent_type_info & eTypeIsReference)
return false;
}
}
return value->IsDereferenceOfParent();
};
if (is_deref_of_parent &&
ValueObject *parent = GetParent();
if (is_deref_of_non_reference(this) &&
epformat == eGetExpressionPathFormatDereferencePointers) {
// this is the original format of GetExpressionPath() producing code like
// *(a_ptr).memberName, which is entirely fine, until you put this into
// StackFrame::GetValueForVariableExpressionPath() which prefers to see
// a_ptr->memberName. the eHonorPointers mode is meant to produce strings
// in this latter format
s.PutCString("*(");
// a_ptr->memberName. The eHonorPointers mode is meant to produce strings
// in this latter format.
s.PutChar('*');
if (parent)
parent->GetExpressionPath(s, epformat);
return;
}
ValueObject *parent = GetParent();
const bool is_deref_of_parent = IsDereferenceOfParent();
bool is_parent_deref_of_non_reference = false;
bool print_obj_access = false;
bool print_ptr_access = false;
if (parent)
parent->GetExpressionPath(s, epformat);
if (!IsBaseClass() && !is_deref_of_parent) {
ValueObject *non_base_class_parent = GetNonBaseClassParent();
if (non_base_class_parent && !non_base_class_parent->GetName().IsEmpty()) {
CompilerType non_base_class_parent_compiler_type =
non_base_class_parent->GetCompilerType();
if (non_base_class_parent_compiler_type) {
if (parent && parent->IsDereferenceOfParent() &&
epformat == eGetExpressionPathFormatHonorPointers) {
print_ptr_access = true;
} else {
const uint32_t non_base_class_parent_type_info =
non_base_class_parent_compiler_type.GetTypeInfo();
// if we are a deref_of_parent just because we are synthetic array members
// made up to allow ptr[%d] syntax to work in variable printing, then add our
// name ([%d]) to the expression path
if (m_flags.m_is_array_item_for_pointer &&
epformat == eGetExpressionPathFormatHonorPointers)
s.PutCString(m_name.GetStringRef());
if (!IsBaseClass()) {
if (!is_deref_of_parent) {
ValueObject *non_base_class_parent = GetNonBaseClassParent();
if (non_base_class_parent &&
!non_base_class_parent->GetName().IsEmpty()) {
CompilerType non_base_class_parent_compiler_type =
non_base_class_parent->GetCompilerType();
if (non_base_class_parent_compiler_type) {
if (parent && parent->IsDereferenceOfParent() &&
epformat == eGetExpressionPathFormatHonorPointers) {
s.PutCString("->");
} else {
const uint32_t non_base_class_parent_type_info =
non_base_class_parent_compiler_type.GetTypeInfo();
if (non_base_class_parent_type_info & eTypeIsPointer) {
s.PutCString("->");
} else if ((non_base_class_parent_type_info & eTypeHasChildren) &&
!(non_base_class_parent_type_info & eTypeIsArray)) {
s.PutChar('.');
}
if (non_base_class_parent_type_info & eTypeIsPointer) {
print_ptr_access = true;
} else if ((non_base_class_parent_type_info & eTypeHasChildren) &&
!(non_base_class_parent_type_info & eTypeIsArray)) {
print_obj_access = true;
}
}
}
const char *name = GetName().GetCString();
if (name)
s.PutCString(name);
is_parent_deref_of_non_reference =
is_deref_of_non_reference(non_base_class_parent) &&
epformat == eGetExpressionPathFormatDereferencePointers;
}
}
if (is_deref_of_parent &&
epformat == eGetExpressionPathFormatDereferencePointers) {
s.PutChar(')');
if (parent) {
// The parent should be wrapped in parenthesis when doing a member access.
// This prevents forming incorrect expressions such as *(ptr).field,
// which dereferences the field instead of the ptr, and constructs the
// expression in the format (*(ptr)).field. To create expressions compatible
// with StackFrame::GetValueForVariableExpressionPath() and reduce amount of
// unnecessary parenthesis, this is done only when the parent has the
// dereference syntax *(parent).
const bool wrap_parent_in_parens = (print_obj_access || print_ptr_access) &&
is_parent_deref_of_non_reference;
if (wrap_parent_in_parens)
s.PutChar('(');
parent->GetExpressionPath(s, epformat);
if (wrap_parent_in_parens)
s.PutChar(')');
}
if (print_obj_access)
s.PutChar('.');
if (print_ptr_access)
s.PutCString("->");
if (!IsBaseClass() && !is_deref_of_parent) {
const char *name = GetName().GetCString();
if (name)
s.PutCString(name);
}
}
@ -3108,8 +3139,6 @@ bool ValueObject::CanProvideValue() {
return (!type.IsValid()) || (0 != (type.GetTypeInfo() & eTypeHasValue));
}
ValueObjectSP ValueObject::Persist() {
if (!UpdateValueIfNeeded())
return nullptr;

2
lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp
View File

@ -6576,6 +6576,8 @@ CompilerType TypeSystemClang::GetChildCompilerTypeAtIndex(
child_is_base_class, tmp_child_is_deref_of_parent, valobj,
language_flags);
} else {
child_is_deref_of_parent = true;
const char *parent_name =
valobj ? valobj->GetName().GetCString() : nullptr;
if (parent_name) {

4
lldb/test/API/functionalities/data-formatter/data-formatter-synth/TestDataFormatterSynth.py
View File

@ -172,8 +172,8 @@ class SynthDataFormatterTestCase(TestBase):
# check flat printing with synthetic children
self.expect('frame variable plenty_of_stuff --flat',
substrs=['plenty_of_stuff.bitfield = 17',
'*(plenty_of_stuff.array) = 5',
'*(plenty_of_stuff.array) = 3'])
'*plenty_of_stuff.array = 5',
'*plenty_of_stuff.array = 3'])
# check that we do not lose location information for our children
self.expect('frame variable plenty_of_stuff --location',

3
lldb/test/API/python_api/expression_path/Makefile Normal file
View File

@ -0,0 +1,3 @@
CXX_SOURCES := main.cpp
include Makefile.rules

119
lldb/test/API/python_api/expression_path/TestExpressionPath.py Normal file
View File

@ -0,0 +1,119 @@
"""Test that SBFrame::GetExpressionPath construct valid expressions"""
import lldb
from lldbsuite.test.decorators import *
from lldbsuite.test.lldbtest import *
from lldbsuite.test import lldbutil
class SBValueGetExpressionPathTest(TestBase):
NO_DEBUG_INFO_TESTCASE = True
def path(self, value):
"""Constructs the expression path given the SBValue"""
if not value:
return None
stream = lldb.SBStream()
if not value.GetExpressionPath(stream):
return None
return stream.GetData()
def test_expression_path(self):
"""Test that SBFrame::GetExpressionPath construct valid expressions"""
self.build()
self.setTearDownCleanup()
exe = self.getBuildArtifact("a.out")
# Create the target
target = self.dbg.CreateTarget(exe)
self.assertTrue(target, VALID_TARGET)
# Set the breakpoints
breakpoint = target.BreakpointCreateBySourceRegex(
'Set breakpoint here', lldb.SBFileSpec("main.cpp"))
self.assertTrue(breakpoint.GetNumLocations() > 0, VALID_BREAKPOINT)
# Launch the process, and do not stop at the entry point.
process = target.LaunchSimple(
None, None, self.get_process_working_directory())
self.assertTrue(process, PROCESS_IS_VALID)
# Frame #0 should be at our breakpoint.
threads = lldbutil.get_threads_stopped_at_breakpoint(
process, breakpoint)
self.assertEquals(len(threads), 1)
self.thread = threads[0]
self.frame = self.thread.frames[0]
self.assertTrue(self.frame, "Frame 0 is valid.")
# Find "b" variables in frame
b = self.frame.FindVariable("b")
bp = self.frame.FindVariable("b_ptr")
br = self.frame.FindVariable("b_ref")
bpr = self.frame.FindVariable("b_ptr_ref")
# Check expression paths
self.assertEqual(self.path(b), "b")
self.assertEqual(self.path(bp), "b_ptr")
self.assertEqual(self.path(br), "b_ref")
self.assertEqual(self.path(bpr), "b_ptr_ref")
# Dereference "b" pointers
bp_deref = bp.Dereference()
bpr_deref = bpr.Dereference() # a pointer
bpr_deref2 = bpr_deref.Dereference() # two Dereference() calls to get object
# Check expression paths
self.assertEqual(self.path(bp_deref), "*b_ptr")
self.assertEqual(self.path(bpr_deref), "b_ptr_ref")
self.assertEqual(self.path(bpr_deref2), "*b_ptr_ref")
# Access "b" members and check expression paths
self.assertEqual(self.path(b.GetChildMemberWithName("x")), "b.x")
self.assertEqual(self.path(bp.GetChildMemberWithName("x")), "b_ptr->x")
self.assertEqual(self.path(br.GetChildMemberWithName("x")), "b_ref.x")
self.assertEqual(self.path(bp_deref.GetChildMemberWithName("x")), "(*b_ptr).x")
self.assertEqual(self.path(bpr_deref.GetChildMemberWithName("x")), "b_ptr_ref->x")
self.assertEqual(self.path(bpr_deref2.GetChildMemberWithName("x")), "(*b_ptr_ref).x")
# TODO: Uncomment once accessing members on pointer references is supported.
# self.assertEqual(self.path(bpr.GetChildMemberWithName("x")), "b_ptr_ref->x")
# Try few expressions with multiple member access
bp_ar_x = bp.GetChildMemberWithName("a_ref").GetChildMemberWithName("x")
br_ar_y = br.GetChildMemberWithName("a_ref").GetChildMemberWithName("y")
self.assertEqual(self.path(bp_ar_x), "b_ptr->a_ref.x")
self.assertEqual(self.path(br_ar_y), "b_ref.a_ref.y")
bpr_deref_apr_deref = bpr_deref.GetChildMemberWithName("a_ptr_ref").Dereference()
bpr_deref_apr_deref2 = bpr_deref_apr_deref.Dereference()
self.assertEqual(self.path(bpr_deref_apr_deref), "b_ptr_ref->a_ptr_ref")
self.assertEqual(self.path(bpr_deref_apr_deref2), "*b_ptr_ref->a_ptr_ref")
bpr_deref_apr_deref_x = bpr_deref_apr_deref.GetChildMemberWithName("x")
bpr_deref_apr_deref2_x = bpr_deref_apr_deref2.GetChildMemberWithName("x")
self.assertEqual(self.path(bpr_deref_apr_deref_x), "b_ptr_ref->a_ptr_ref->x")
self.assertEqual(self.path(bpr_deref_apr_deref2_x), "(*b_ptr_ref->a_ptr_ref).x")
# Find "c" variables in frame
c = self.frame.FindVariable("c")
cp = self.frame.FindVariable("c_ptr")
cr = self.frame.FindVariable("c_ref")
cpr = self.frame.FindVariable("c_ptr_ref")
# Dereference pointers
cp_deref = cp.Dereference()
cpr_deref = cpr.Dereference() # a pointer
cpr_deref2 = cpr_deref.Dereference() # two Dereference() calls to get object
# Check expression paths
self.assertEqual(self.path(cp_deref), "*c_ptr")
self.assertEqual(self.path(cpr_deref), "c_ptr_ref")
self.assertEqual(self.path(cpr_deref2), "*c_ptr_ref")
# Access members on "c" variables and check expression paths
self.assertEqual(self.path(c.GetChildMemberWithName("x")), "c.x")
self.assertEqual(self.path(cp.GetChildMemberWithName("x")), "c_ptr->x")
self.assertEqual(self.path(cr.GetChildMemberWithName("x")), "c_ref.x")
self.assertEqual(self.path(cp_deref.GetChildMemberWithName("x")), "(*c_ptr).x")
self.assertEqual(self.path(cpr_deref.GetChildMemberWithName("x")), "c_ptr_ref->x")
self.assertEqual(self.path(cpr_deref2.GetChildMemberWithName("x")), "(*c_ptr_ref).x")
# TODO: Uncomment once accessing members on pointer references is supported.
# self.assertEqual(self.path(cpr.GetChildMemberWithName("x")), "c_ptr_ref->x")

34
lldb/test/API/python_api/expression_path/main.cpp Normal file
View File

@ -0,0 +1,34 @@
struct StructA {
int x;
int y;
};
struct StructB {
int x;
StructA &a_ref;
StructA *&a_ptr_ref;
};
struct StructC : public StructB {
int y;
StructC(int x, StructA &a_ref, StructA *&a_ref_ptr, int y)
: StructB{x, a_ref, a_ref_ptr}, y(y) {}
};
int main() {
StructA a{1, 2};
StructA *a_ptr = &a;
StructB b{3, a, a_ptr};
StructB *b_ptr = &b;
StructB &b_ref = b;
StructB *&b_ptr_ref = b_ptr;
StructC c(4, a, a_ptr, 5);
StructC *c_ptr = &c;
StructC &c_ref = c;
StructC *&c_ptr_ref = c_ptr;
return 0; // Set breakpoint here
}