[StringList] Change LongestCommonPrefix API

When investigating a completion bug I got confused by the API.
LongestCommonPrefix finds the longest common prefix of the strings in
the string list. Instead of returning that string through an output
argument, just return it by value.

llvm-svn: 367384

1 files changed, 3 insertions, 4 deletions

diff --git a/lldb/source/Utility/StringList.cpp b/lldb/source/Utility/StringList.cpp
index fb0d9be8797..03249e00ccc 100644
--- a/lldb/source/Utility/StringList.cpp
+++ b/lldb/source/Utility/StringList.cpp
@@ -100,10 +100,9 @@ void StringList::Join(const char *separator, Stream &strm) {
 
 void StringList::Clear() { m_strings.clear(); }
 
-void StringList::LongestCommonPrefix(std::string &common_prefix) {
-  common_prefix.clear();
+std::string StringList::LongestCommonPrefix() {
   if (m_strings.empty())
-    return;
+    return {};
 
   auto args = llvm::makeArrayRef(m_strings);
   llvm::StringRef prefix = args.front();
@@ -115,7 +114,7 @@ void StringList::LongestCommonPrefix(std::string &common_prefix) {
     }
     prefix = prefix.take_front(count);
   }
-  common_prefix = prefix;
+  return prefix.str();
 }
 
 void StringList::InsertStringAtIndex(size_t idx, const char *str) {