From 2b04a86d4d7398947aab66ebfcd4ce3b0392383f Mon Sep 17 00:00:00 2001
From: Itamar <itamar8910@gmail.com>
Date: Tue, 28 Sep 2021 13:26:49 +0300
Subject: [PATCH] LibDebug: Add Dwarf::CompilationUnit::base_address()

The base address of the compilation unit is used in some range lists
entry types.
---
 .../Libraries/LibDebug/Dwarf/CompilationUnit.cpp   | 14 ++++++++++++++
 .../Libraries/LibDebug/Dwarf/CompilationUnit.h     |  3 +++
 2 files changed, 17 insertions(+)

diff --git a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp
index 07ffc30993..d78472cc7b 100644
--- a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp
+++ b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.cpp
@@ -30,4 +30,18 @@ DIE CompilationUnit::get_die_at_offset(u32 die_offset) const
     return DIE(*this, die_offset);
 }
 
+Optional<FlatPtr> CompilationUnit::base_address() const
+{
+    if (m_has_cached_base_address)
+        return m_cached_base_address;
+
+    auto die = root_die();
+    auto res = die.get_attribute(Attribute::LowPc);
+    if (res.has_value()) {
+        m_cached_base_address = res->data.as_addr;
+    }
+    m_has_cached_base_address = true;
+    return m_cached_base_address;
+}
+
 }
diff --git a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h
index 5acb1a2088..c860d1237a 100644
--- a/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h
+++ b/Userland/Libraries/LibDebug/Dwarf/CompilationUnit.h
@@ -34,6 +34,7 @@ public:
     DwarfInfo const& dwarf_info() const { return m_dwarf_info; }
     AbbreviationsMap const& abbreviations_map() const { return m_abbreviations; }
     LineProgram const& line_program() const { return *m_line_program; }
+    Optional<FlatPtr> base_address() const;
 
 private:
     DwarfInfo const& m_dwarf_info;
@@ -41,6 +42,8 @@ private:
     CompilationUnitHeader m_header;
     AbbreviationsMap m_abbreviations;
     NonnullOwnPtr<LineProgram> m_line_program;
+    mutable bool m_has_cached_base_address { false };
+    mutable Optional<FlatPtr> m_cached_base_address;
 };
 
 }