From 06c9c14995aebb2dc63926099778b77a402e82ae Mon Sep 17 00:00:00 2001
From: Jeremy Rifkin <51220084+jeremy-rifkin@users.noreply.github.com>
Date: Tue, 28 Jan 2025 23:26:28 -0600
Subject: [PATCH] Return an optional from lookup_symbol

---
 src/binary/elf.cpp                    | 15 ++++++++-------
 src/binary/elf.hpp                    |  2 +-
 src/binary/mach-o.cpp                 |  6 +++---
 src/binary/mach-o.hpp                 |  2 +-
 src/symbols/symbols_with_libdwarf.cpp |  2 +-
 5 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/src/binary/elf.cpp b/src/binary/elf.cpp
index 7dcf956..83ca628 100644
--- a/src/binary/elf.cpp
+++ b/src/binary/elf.cpp
@@ -1,4 +1,5 @@
 #include "binary/elf.hpp"
+#include "utils/optional.hpp"
 
 #if IS_LINUX
 
@@ -88,23 +89,23 @@ namespace detail {
         return 0;
     }
 
-    std::string elf::lookup_symbol(frame_ptr pc) {
+    optional<std::string> elf::lookup_symbol(frame_ptr pc) {
         // TODO: Also search the SHT_DYNSYM at some point, maybe
         auto symtab_ = get_symtab();
         if(symtab_.is_error()) {
-            return "";
+            return nullopt;
         }
         auto& maybe_symtab = symtab_.unwrap_value();
         if(!maybe_symtab) {
-            return "";
+            return nullopt;
         }
         auto& symtab = maybe_symtab.unwrap();
         if(symtab.strtab_link == SHN_UNDEF) {
-            return "";
+            return nullopt;
         }
         auto strtab_ = get_strtab(symtab.strtab_link);
         if(strtab_.is_error()) {
-            return "";
+            return nullopt;
         }
         auto& strtab = strtab_.unwrap_value();
         auto it = first_less_than_or_equal(
@@ -116,12 +117,12 @@ namespace detail {
             }
         );
         if(it == symtab.entries.end()) {
-            return "";
+            return nullopt;
         }
         if(pc <= it->st_value + it->st_size) {
             return strtab.data() + it->st_name;
         }
-        return "";
+        return nullopt;
     }
 
     template<typename T, typename std::enable_if<std::is_integral<T>::value, int>::type>
diff --git a/src/binary/elf.hpp b/src/binary/elf.hpp
index 102ea49..59fe90e 100644
--- a/src/binary/elf.hpp
+++ b/src/binary/elf.hpp
@@ -76,7 +76,7 @@ namespace detail {
         Result<std::uintptr_t, internal_error> get_module_image_base_impl();
 
     public:
-        std::string lookup_symbol(frame_ptr pc);
+        optional<std::string> lookup_symbol(frame_ptr pc);
 
     private:
         template<typename T, typename std::enable_if<std::is_integral<T>::value, int>::type = 0>
diff --git a/src/binary/mach-o.cpp b/src/binary/mach-o.cpp
index d25a41e..90823c6 100644
--- a/src/binary/mach-o.cpp
+++ b/src/binary/mach-o.cpp
@@ -416,10 +416,10 @@ namespace detail {
         return symbols.unwrap();
     }
 
-    std::string mach_o::lookup_symbol(frame_ptr pc) {
+    optional<std::string> mach_o::lookup_symbol(frame_ptr pc) {
         auto symtab_ = symbol_table();
         if(!symtab_) {
-            return "";
+            return nullopt;
         }
         const auto& symtab = symtab_.unwrap_value();;
         auto it = first_less_than_or_equal(
@@ -431,7 +431,7 @@ namespace detail {
             }
         );
         if(it == symtab.end()) {
-            return "";
+            return nullopt;
         }
         ASSERT(pc >= it->address);
         // TODO: We subtracted one from the address so name + diff won't show up in the objdump, decide if desirable
diff --git a/src/binary/mach-o.hpp b/src/binary/mach-o.hpp
index 82a36c5..506756e 100644
--- a/src/binary/mach-o.hpp
+++ b/src/binary/mach-o.hpp
@@ -112,7 +112,7 @@ namespace detail {
 
         Result<const std::vector<symbol_entry>&, internal_error> symbol_table();
 
-        std::string lookup_symbol(frame_ptr pc);
+        optional<std::string> lookup_symbol(frame_ptr pc);
 
         // produce information similar to dsymutil -dump-debug-map
         static void print_debug_map(const debug_map& debug_map);
diff --git a/src/symbols/symbols_with_libdwarf.cpp b/src/symbols/symbols_with_libdwarf.cpp
index dcbfa3c..abd54cf 100644
--- a/src/symbols/symbols_with_libdwarf.cpp
+++ b/src/symbols/symbols_with_libdwarf.cpp
@@ -116,7 +116,7 @@ namespace libdwarf {
                     }
                     #if IS_LINUX || IS_APPLE
                     if(frame.frame.symbol.empty() && object.has_value()) {
-                        frame.frame.symbol = object.unwrap_value().lookup_symbol(dlframe.object_address);
+                        frame.frame.symbol = object.unwrap_value().lookup_symbol(dlframe.object_address).value_or("");
                     }
                     #endif
                 }