[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

1 files changed, 22 insertions, 59 deletions

diff --git a/lldb/source/Commands/CommandObjectSource.cpp b/lldb/source/Commands/CommandObjectSource.cpp
index 44561cf..bbc3142 100644
--- a/lldb/source/Commands/CommandObjectSource.cpp
+++ b/lldb/source/Commands/CommandObjectSource.cpp
@@ -146,10 +146,7 @@ protected:
     uint32_t num_matches = 0;
     // Dump all the line entries for the file in the list.
     ConstString last_module_file_name;
-    uint32_t num_scs = sc_list.GetSize();
-    for (uint32_t i = 0; i < num_scs; ++i) {
-      SymbolContext sc;
-      sc_list.GetContextAtIndex(i, sc);
+    for (const SymbolContext &sc : sc_list) {
       if (sc.comp_unit) {
         Module *module = sc.module_sp.get();
         CompileUnit *cu = sc.comp_unit;
@@ -393,10 +390,7 @@ protected:
       SymbolContextList sc_list_symbols;
       module_list.FindFunctionSymbols(name, eFunctionNameTypeAuto,
                                       sc_list_symbols);
-      size_t num_symbol_matches = sc_list_symbols.GetSize();
-      for (size_t i = 0; i < num_symbol_matches; i++) {
-        SymbolContext sc;
-        sc_list_symbols.GetContextAtIndex(i, sc);
+      for (const SymbolContext &sc : sc_list_symbols) {
         if (sc.symbol && sc.symbol->ValueIsAddress()) {
           const Address &base_address = sc.symbol->GetAddressRef();
           Function *function = base_address.CalculateSymbolContextFunction();
@@ -412,9 +406,7 @@ protected:
                                    m_options.symbol_name.c_str());
       return false;
     }
-    for (size_t i = 0; i < num_matches; i++) {
-      SymbolContext sc;
-      sc_list_funcs.GetContextAtIndex(i, sc);
+    for (const SymbolContext &sc : sc_list_funcs) {
       bool context_found_for_symbol = false;
       // Loop through all the ranges in the function.
       AddressRange range;
@@ -926,69 +918,45 @@ protected:
 
       // Displaying the source for a symbol. Search for function named name.
       FindMatchingFunctions(target, name, sc_list);
-      size_t num_matches = sc_list.GetSize();
-      if (!num_matches) {
+      if (sc_list.GetSize() == 0) {
         // If we didn't find any functions with that name, try searching for
         // symbols that line up exactly with function addresses.
         SymbolContextList sc_list_symbols;
         FindMatchingFunctionSymbols(target, name, sc_list_symbols);
-        size_t num_symbol_matches = sc_list_symbols.GetSize();
-
-        for (size_t i = 0; i < num_symbol_matches; i++) {
-          SymbolContext sc;
-          sc_list_symbols.GetContextAtIndex(i, sc);
+        for (const SymbolContext &sc : sc_list_symbols) {
           if (sc.symbol && sc.symbol->ValueIsAddress()) {
             const Address &base_address = sc.symbol->GetAddressRef();
             Function *function = base_address.CalculateSymbolContextFunction();
             if (function) {
               sc_list.Append(SymbolContext(function));
-              num_matches++;
               break;
             }
           }
         }
       }
 
-      if (num_matches == 0) {
+      if (sc_list.GetSize() == 0) {
         result.AppendErrorWithFormat("Could not find function named: \"%s\".\n",
                                      m_options.symbol_name.c_str());
         return false;
       }
 
-      if (num_matches > 1) {
-        std::set<SourceInfo> source_match_set;
-
-        bool displayed_something = false;
-        for (size_t i = 0; i < num_matches; i++) {
-          SymbolContext sc;
-          sc_list.GetContextAtIndex(i, sc);
-          SourceInfo source_info(sc.GetFunctionName(),
-                                 sc.GetFunctionStartLineEntry());
-
-          if (source_info.IsValid()) {
-            if (source_match_set.find(source_info) == source_match_set.end()) {
-              source_match_set.insert(source_info);
-              if (DisplayFunctionSource(sc, source_info, result))
-                displayed_something = true;
-            }
-          }
-        }
-
-        if (displayed_something)
-          result.SetStatus(eReturnStatusSuccessFinishResult);
-        else
-          result.SetStatus(eReturnStatusFailed);
-      } else {
-        SymbolContext sc;
-        sc_list.GetContextAtIndex(0, sc);
-        SourceInfo source_info;
-
-        if (DisplayFunctionSource(sc, source_info, result)) {
-          result.SetStatus(eReturnStatusSuccessFinishResult);
-        } else {
-          result.SetStatus(eReturnStatusFailed);
+      std::set<SourceInfo> source_match_set;
+      bool displayed_something = false;
+      for (const SymbolContext &sc : sc_list) {
+        SourceInfo source_info(sc.GetFunctionName(),
+                               sc.GetFunctionStartLineEntry());
+        if (source_info.IsValid() &&
+            source_match_set.find(source_info) == source_match_set.end()) {
+          source_match_set.insert(source_info);
+          if (DisplayFunctionSource(sc, source_info, result))
+            displayed_something = true;
         }
       }
+      if (displayed_something)
+        result.SetStatus(eReturnStatusSuccessFinishResult);
+      else
+        result.SetStatus(eReturnStatusFailed);
       return result.Succeeded();
     } else if (m_options.address != LLDB_INVALID_ADDRESS) {
       Address so_addr;
@@ -1052,10 +1020,7 @@ protected:
           return false;
         }
       }
-      uint32_t num_matches = sc_list.GetSize();
-      for (uint32_t i = 0; i < num_matches; ++i) {
-        SymbolContext sc;
-        sc_list.GetContextAtIndex(i, sc);
+      for (const SymbolContext &sc : sc_list) {
         if (sc.comp_unit) {
           if (m_options.show_bp_locs) {
             m_breakpoint_locations.Clear();
@@ -1175,9 +1140,7 @@ protected:
         bool got_multiple = false;
         CompileUnit *test_cu = nullptr;
 
-        for (unsigned i = 0; i < num_matches; i++) {
-          SymbolContext sc;
-          sc_list.GetContextAtIndex(i, sc);
+        for (const SymbolContext &sc : sc_list) {
           if (sc.comp_unit) {
             if (test_cu) {
               if (test_cu != sc.comp_unit)