cmLinkItem: Convert to a "sum type" over a string and target pointer

Avoid exposing the item name implicitly as std::string.  When the item
is a target, avoid storing a second copy of its name.

Most link item construction is paired with calls to `FindTargetToLink`
to get the possible target pointer.  Rename these methods to
`ResolveLinkItem` and refactor them to construct the entire item.

1 files changed, 16 insertions, 14 deletions

diff --git a/Source/cmComputeLinkDepends.cxx b/Source/cmComputeLinkDepends.cxx
index b1f3860..3659a1e 100644
--- a/Source/cmComputeLinkDepends.cxx
+++ b/Source/cmComputeLinkDepends.cxx
@@ -295,22 +295,24 @@ std::map<std::string, int>::iterator cmComputeLinkDepends::AllocateLinkEntry(
 int cmComputeLinkDepends::AddLinkEntry(cmLinkItem const& item)
 {
   // Check if the item entry has already been added.
-  std::map<std::string, int>::iterator lei = this->LinkEntryIndex.find(item);
+  std::map<std::string, int>::iterator lei =
+    this->LinkEntryIndex.find(item.AsStr());
   if (lei != this->LinkEntryIndex.end()) {
     // Yes.  We do not need to follow the item's dependencies again.
     return lei->second;
   }
 
   // Allocate a spot for the item entry.
-  lei = this->AllocateLinkEntry(item);
+  lei = this->AllocateLinkEntry(item.AsStr());
 
   // Initialize the item entry.
   int index = lei->second;
   LinkEntry& entry = this->EntryList[index];
-  entry.Item = item;
+  entry.Item = item.AsStr();
   entry.Target = item.Target;
-  entry.IsFlag = (!entry.Target && item[0] == '-' && item[1] != 'l' &&
-                  item.substr(0, 10) != "-framework");
+  entry.IsFlag =
+    (!entry.Target && entry.Item[0] == '-' && entry.Item[1] != 'l' &&
+     entry.Item.substr(0, 10) != "-framework");
 
   // If the item has dependencies queue it to follow them.
   if (entry.Target) {
@@ -396,14 +398,14 @@ void cmComputeLinkDepends::HandleSharedDependency(SharedDepEntry const& dep)
 {
   // Check if the target already has an entry.
   std::map<std::string, int>::iterator lei =
-    this->LinkEntryIndex.find(dep.Item);
+    this->LinkEntryIndex.find(dep.Item.AsStr());
   if (lei == this->LinkEntryIndex.end()) {
     // Allocate a spot for the item entry.
-    lei = this->AllocateLinkEntry(dep.Item);
+    lei = this->AllocateLinkEntry(dep.Item.AsStr());
 
     // Initialize the item entry.
     LinkEntry& entry = this->EntryList[lei->second];
-    entry.Item = dep.Item;
+    entry.Item = dep.Item.AsStr();
     entry.Target = dep.Item.Target;
 
     // This item was added specifically because it is a dependent
@@ -473,9 +475,9 @@ void cmComputeLinkDepends::AddVarLinkEntries(int depender_index,
 
       // If the library is meant for this link type then use it.
       if (llt == GENERAL_LibraryType || llt == this->LinkType) {
-        actual_libs.emplace_back(d, this->FindTargetToLink(depender_index, d));
+        actual_libs.emplace_back(this->ResolveLinkItem(depender_index, d));
       } else if (this->OldLinkDirMode) {
-        cmLinkItem item(d, this->FindTargetToLink(depender_index, d));
+        cmLinkItem item = this->ResolveLinkItem(depender_index, d);
         this->CheckWrongConfigItem(item);
       }
 
@@ -512,7 +514,7 @@ void cmComputeLinkDepends::AddLinkEntries(int depender_index,
     // Skip entries that will resolve to the target getting linked or
     // are empty.
     cmLinkItem const& item = l;
-    if (item == this->Target->GetName() || item.empty()) {
+    if (item.AsStr() == this->Target->GetName() || item.AsStr().empty()) {
       continue;
     }
 
@@ -553,8 +555,8 @@ void cmComputeLinkDepends::AddLinkEntries(int depender_index,
   }
 }
 
-cmGeneratorTarget const* cmComputeLinkDepends::FindTargetToLink(
-  int depender_index, const std::string& name)
+cmLinkItem cmComputeLinkDepends::ResolveLinkItem(int depender_index,
+                                                 const std::string& name)
 {
   // Look for a target in the scope of the depender.
   cmGeneratorTarget const* from = this->Target;
@@ -564,7 +566,7 @@ cmGeneratorTarget const* cmComputeLinkDepends::FindTargetToLink(
       from = depender;
     }
   }
-  return from->FindTargetToLink(name);
+  return from->ResolveLinkItem(name);
 }
 
 void cmComputeLinkDepends::InferDependencies()