[Lldb-commits] [lldb] [lldb] Add SetValueFromCString API to SyntheticFronend (PR #67309)

[Pavel Kosov via lldb-commits]

https://github.com/kpdev updated https://github.com/llvm/llvm-project/pull/67309

>From a0aae1f59fcdc9f0266bdc6248544f674b298e85 Mon Sep 17 00:00:00 2001
From: Pavel Kosov <kpdev42 at gmail.com>
Date: Mon, 25 Sep 2023 13:41:03 +0300
Subject: [PATCH] [lldb] Add SetValueFromCString API to SyntheticFronend

It is a first of three patches neded for adding an ability to update std::string/wstring/etc during debug process.
Add SetValueFromCString API to SyntheticFronend

Overall context is avaliable in the following discussion: https://discourse.llvm.org/t/clarify-hostaddress-loadaddress-logic/72175/3:

~~

Huawei RRI, OS Lab
---
 lldb/include/lldb/Core/ValueObject.h             | 11 +++++++++++
 lldb/include/lldb/DataFormatters/TypeSynthetic.h | 12 ++++++++++--
 lldb/source/Core/ValueObject.cpp                 |  9 +++++++--
 3 files changed, 28 insertions(+), 4 deletions(-)

diff --git a/lldb/include/lldb/Core/ValueObject.h b/lldb/include/lldb/Core/ValueObject.h
index 3af94f0a86e2fcc..892f5d0dea4f650 100644
--- a/lldb/include/lldb/Core/ValueObject.h
+++ b/lldb/include/lldb/Core/ValueObject.h
@@ -589,6 +589,14 @@ class ValueObject {
 
   virtual bool IsSynthetic() { return false; }
 
+  void SetSyntheticFrontend(SyntheticChildrenFrontEnd *synth_front) {
+    m_synthetic_frontend = synth_front;
+  }
+
+  SyntheticChildrenFrontEnd *GetSyntheticFrontend() const {
+    return m_synthetic_frontend;
+  }
+
   lldb::ValueObjectSP
   GetQualifiedRepresentationIfAvailable(lldb::DynamicValueType dynValue,
                                         bool synthValue);
@@ -898,6 +906,9 @@ class ValueObject {
   /// Unique identifier for every value object.
   UserID m_id;
 
+  // If frontend exist - we may try to update our value through it
+  SyntheticChildrenFrontEnd *m_synthetic_frontend = nullptr;
+
   // Utility class for initializing all bitfields in ValueObject's constructors.
   // FIXME: This could be done via default initializers once we have C++20.
   struct Bitflags {
diff --git a/lldb/include/lldb/DataFormatters/TypeSynthetic.h b/lldb/include/lldb/DataFormatters/TypeSynthetic.h
index 41be9b7efda8fdb..8e9bf9da77211ba 100644
--- a/lldb/include/lldb/DataFormatters/TypeSynthetic.h
+++ b/lldb/include/lldb/DataFormatters/TypeSynthetic.h
@@ -34,9 +34,13 @@ class SyntheticChildrenFrontEnd {
 
 public:
   SyntheticChildrenFrontEnd(ValueObject &backend)
-      : m_backend(backend), m_valid(true) {}
+      : m_backend(backend), m_valid(true) {
+    m_backend.SetSyntheticFrontend(this);
+  }
 
-  virtual ~SyntheticChildrenFrontEnd() = default;
+  virtual ~SyntheticChildrenFrontEnd() {
+    m_backend.SetSyntheticFrontend(nullptr);
+  }
 
   virtual size_t CalculateNumChildren() = 0;
 
@@ -75,6 +79,10 @@ class SyntheticChildrenFrontEnd {
   // display purposes
   virtual ConstString GetSyntheticTypeName() { return ConstString(); }
 
+  virtual bool SetValueFromCString(const char *value_str, Status &error) {
+    return false;
+  }
+
   typedef std::shared_ptr<SyntheticChildrenFrontEnd> SharedPointer;
   typedef std::unique_ptr<SyntheticChildrenFrontEnd> AutoPointer;
 
diff --git a/lldb/source/Core/ValueObject.cpp b/lldb/source/Core/ValueObject.cpp
index ebfc1cf4d6fe9e1..e6ae56045d5f3ba 100644
--- a/lldb/source/Core/ValueObject.cpp
+++ b/lldb/source/Core/ValueObject.cpp
@@ -1479,7 +1479,7 @@ bool ValueObject::SetValueFromCString(const char *value_str, Status &error) {
   if (value_type == Value::ValueType::Scalar) {
     // If the value is already a scalar, then let the scalar change itself:
     m_value.GetScalar().SetValueFromCString(value_str, encoding, byte_size);
-  } else if (byte_size <= 16) {
+  } else if (byte_size <= 16 && encoding != eEncodingInvalid) {
     // If the value fits in a scalar, then make a new scalar and again let the
     // scalar code do the conversion, then figure out where to put the new
     // value.
@@ -1535,7 +1535,12 @@ bool ValueObject::SetValueFromCString(const char *value_str, Status &error) {
     }
   } else {
     // We don't support setting things bigger than a scalar at present.
-    error.SetErrorString("unable to write aggregate data type");
+    // But maybe our frontend knows how to update the value.
+    if (auto *frontend = GetSyntheticFrontend()) {
+      return frontend->SetValueFromCString(value_str, error);
+    } else {
+      error.SetErrorString("unable to write aggregate data type");
+    }
     return false;
   }