cmGeneratorTarget: add the concept of a "family" name

With synthetic targets, a name which is the same between all synthetic
targets which share a base target is warranted.

Source/cmGeneratorTarget.cxx

@@ -173,6 +173,20 @@ const std::string& cmGeneratorTarget::GetName() const
   return this->Target->GetName();
 }
 
+std::string cmGeneratorTarget::GetFamilyName() const
+{
+  if (!this->IsImported() && !this->IsSynthetic()) {
+    return this->Target->GetTemplateName();
+  }
+  cmCryptoHash hasher(cmCryptoHash::AlgoSHA3_512);
+  constexpr size_t HASH_TRUNCATION = 12;
+  auto dirhash =
+    hasher.HashString(this->GetLocalGenerator()->GetCurrentBinaryDirectory());
+  auto targetIdent = hasher.HashString(cmStrCat("@d_", dirhash));
+  return cmStrCat(this->Target->GetTemplateName(), '@',
+                  targetIdent.substr(0, HASH_TRUNCATION));
+}
+
 std::string cmGeneratorTarget::GetExportName() const
 {
   cmValue exportName = this->GetProperty("EXPORT_NAME");

Source/cmGeneratorTarget.h

@@ -108,6 +108,7 @@ public:
 
   cmStateEnums::TargetType GetType() const;
   const std::string& GetName() const;
+  std::string GetFamilyName() const;
   std::string GetExportName() const;
   std::string GetFilesystemExportName() const;
 

Source/cmTarget.cxx

@@ -645,6 +645,7 @@ public:
   cmStateEnums::TargetType TargetType;
   cmMakefile* Makefile;
   cmPolicies::PolicyMap PolicyMap;
+  cmTarget const* TemplateTarget;
   std::string Name;
   std::string InstallPath;
   std::string RuntimeInstallPath;
@@ -931,6 +932,7 @@ cmTarget::cmTarget(std::string const& name, cmStateEnums::TargetType type,
   this->impl->TargetType = type;
   this->impl->Makefile = mf;
   this->impl->Name = name;
+  this->impl->TemplateTarget = nullptr;
   this->impl->IsGeneratorProvided = false;
   this->impl->HaveInstallRule = false;
   this->impl->IsDLLPlatform = false;
@@ -1186,6 +1188,14 @@ const std::string& cmTarget::GetName() const
   return this->impl->Name;
 }
 
+const std::string& cmTarget::GetTemplateName() const
+{
+  if (this->impl->TemplateTarget) {
+    return this->impl->TemplateTarget->GetTemplateName();
+  }
+  return this->impl->Name;
+}
+
 cmPolicies::PolicyStatus cmTarget::GetPolicyStatus(
   cmPolicies::PolicyID policy) const
 {
@@ -1784,6 +1794,7 @@ void cmTarget::CopyPolicyStatuses(cmTarget const* tgt)
   assert(tgt->IsImported());
 
   this->impl->PolicyMap = tgt->impl->PolicyMap;
+  this->impl->TemplateTarget = tgt;
 }
 
 void cmTarget::CopyImportedCxxModulesEntries(cmTarget const* tgt)

Source/cmTarget.h

@@ -78,6 +78,7 @@ public:
 
   //! Set/Get the name of the target
   const std::string& GetName() const;
+  const std::string& GetTemplateName() const;
 
   //! Get the policy map
   cmPolicies::PolicyMap const& GetPolicyMap() const;