[Lldb-commits] [lldb] [lldb] Prevent early exit for weak symbol found in IRExecutionUnit::FindInSymbols (PR #161733)

[Dave Lee via lldb-commits]

https://github.com/kastiglione created https://github.com/llvm/llvm-project/pull/161733

`LoadAddressResolver::Resolve` returns zero for weak symbols. However `FindInSymbols`
does multiple searches (each starting with `FindSymbolsWithNameAndType`), and a resolved
address of zero from one step of the search should not conclude the search.

This change continues the searching for a symbol by only performing an early exit when a
concrete address is found.

This was identified by an objc class which is available only in newer OSes. Such classes
are weak linked. Expressions involving this class were failing, because the search first
found the weak linked symbol.

rdar://161406615


>From f329ebfc7b855177c9b9df428826d3bc3e4c0c9a Mon Sep 17 00:00:00 2001
From: Dave Lee <davelee.com at gmail.com>
Date: Thu, 2 Oct 2025 13:42:07 -0700
Subject: [PATCH] [lldb] Prevent early exit for weak symbol found in
 IRExecutionUnit::FindInSymbols

`LoadAddressResolver::Resolve` returns zero for weak symbols. However `FindInSymbols`
does multiple searches (each starting with `FindSymbolsWithNameAndType`), and a resolved
address of zero from one step of the search should not conclude the search.

This change continues the searching for a symbol by only performing an early exit when a
concrete address is found.

This was identified by an objc class which is available only in newer OSes. Such classes
are weak linked. Expressions involving this class were failing, because the search first
found the weak linked symbol.

rdar://161406615
---
 lldb/source/Expression/IRExecutionUnit.cpp | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/lldb/source/Expression/IRExecutionUnit.cpp b/lldb/source/Expression/IRExecutionUnit.cpp
index 60b9de0d21b2e..212a62e3142cd 100644
--- a/lldb/source/Expression/IRExecutionUnit.cpp
+++ b/lldb/source/Expression/IRExecutionUnit.cpp
@@ -822,7 +822,8 @@ IRExecutionUnit::FindInSymbols(const std::vector<ConstString> &names,
       sc.module_sp->FindSymbolsWithNameAndType(name, lldb::eSymbolTypeAny,
                                                sc_list);
       if (auto load_addr = resolver.Resolve(sc_list))
-        return *load_addr;
+        if (!symbol_was_missing_weak)
+          return *load_addr;
     }
 
     {
@@ -830,7 +831,8 @@ IRExecutionUnit::FindInSymbols(const std::vector<ConstString> &names,
       m_preferred_modules.FindSymbolsWithNameAndType(name, lldb::eSymbolTypeAny,
                                                      sc_list);
       if (auto load_addr = resolver.Resolve(sc_list))
-        return *load_addr;
+        if (!symbol_was_missing_weak)
+          return *load_addr;
     }
 
     {
@@ -838,7 +840,8 @@ IRExecutionUnit::FindInSymbols(const std::vector<ConstString> &names,
       non_local_images.FindSymbolsWithNameAndType(name, lldb::eSymbolTypeAny,
                                                   sc_list);
       if (auto load_addr = resolver.Resolve(sc_list))
-        return *load_addr;
+        if (!symbol_was_missing_weak)
+          return *load_addr;
     }
 
     lldb::addr_t best_internal_load_address =