[lldb] Expose a const iterator for SymbolContextList

There are many situations where we'll iterate over a SymbolContextList
with the pattern:
```
SymbolContextList sc_list;
// Fill in sc_list here
for (auto i = 0; i < sc_list.GetSize(); i++) {
  SymbolContext sc;
  sc_list.GetSymbolAtContext(i, sc);

  // Do work with sc
}
```
Adding an iterator to iterate over the instances directly means we don't
have to do bounds checking or create a copy of every element of the
SymbolContextList.

Differential Revision: https://reviews.llvm.org/D149900

3 files changed, 7 insertions, 3 deletions

diff --git a/lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h b/lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h
index 5864a284d6f1..3747e6d2d9a2 100644
--- a/lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h
+++ b/lldb/include/lldb/Breakpoint/BreakpointResolverFileLine.h
@@ -59,7 +59,7 @@ public:
 
 protected:
   void FilterContexts(SymbolContextList &sc_list);
-  void DeduceSourceMapping(SymbolContextList &sc_list);
+  void DeduceSourceMapping(const SymbolContextList &sc_list);
 
   friend class Breakpoint;
   SourceLocationSpec m_location_spec;
diff --git a/lldb/include/lldb/Symbol/SymbolContext.h b/lldb/include/lldb/Symbol/SymbolContext.h
index 73fa25514aff..68bef70f3bcf 100644
--- a/lldb/include/lldb/Symbol/SymbolContext.h
+++ b/lldb/include/lldb/Symbol/SymbolContext.h
@@ -451,11 +451,15 @@ public:
 protected:
   typedef std::vector<SymbolContext>
       collection; ///< The collection type for the list.
+  typedef collection::const_iterator const_iterator;
 
   // Member variables.
   collection m_symbol_contexts; ///< The list of symbol contexts.
 
 public:
+  const_iterator begin() const { return m_symbol_contexts.begin(); }
+  const_iterator end() const { return m_symbol_contexts.end(); }
+
   typedef AdaptedIterable<collection, SymbolContext, vector_adapter>
       SymbolContextIterable;
   SymbolContextIterable SymbolContexts() {
diff --git a/lldb/include/lldb/Symbol/UnwindTable.h b/lldb/include/lldb/Symbol/UnwindTable.h
index a3026504dbdf..f0ce7047de2d 100644
--- a/lldb/include/lldb/Symbol/UnwindTable.h
+++ b/lldb/include/lldb/Symbol/UnwindTable.h
@@ -53,7 +53,7 @@ public:
   // problem.
   lldb::FuncUnwindersSP
   GetUncachedFuncUnwindersContainingAddress(const Address &addr,
-                                            SymbolContext &sc);
+                                            const SymbolContext &sc);
 
   ArchSpec GetArchitecture();
 
@@ -62,7 +62,7 @@ private:
 
   void Initialize();
   std::optional<AddressRange> GetAddressRange(const Address &addr,
-                                              SymbolContext &sc);
+                                              const SymbolContext &sc);
 
   typedef std::map<lldb::addr_t, lldb::FuncUnwindersSP> collection;
   typedef collection::iterator iterator;