From f3d2eab36a0b3bf259dfe847b42bfe0b46447107 Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Tue, 18 Jan 2022 16:45:06 -0500
Subject: cmGeneratorTarget: Fix link interface caching of partial results

`GetLinkInterface` and `GetLinkInterfaceLibraries` cache their results
to avoid repeating work.  In the case that the result does not depend on
the "head" target, they re-use results computed from the first call with
any "head" target.  However, if `GetLinkInterfaceLibraries` is called
first, then not all of the link interface is populated.  If
`GetLinkInterface` is later called, it needs to finish populating the
link interface even if a partially completed interface was cached.
---
 Source/cmGeneratorTarget.cxx | 30 ++++++++++++++----------------
 1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/Source/cmGeneratorTarget.cxx b/Source/cmGeneratorTarget.cxx
index f78b12b..5ec6832 100644
--- a/Source/cmGeneratorTarget.cxx
+++ b/Source/cmGeneratorTarget.cxx
@@ -6746,17 +6746,16 @@ cmLinkInterface const* cmGeneratorTarget::GetLinkInterface(
   // Lookup any existing link interface for this configuration.
   cmHeadToLinkInterfaceMap& hm = this->GetHeadToLinkInterfaceMap(config);
 
-  if (secondPass) {
-    hm.erase(head);
-  }
-
   // If the link interface does not depend on the head target
-  // then return the one we computed first.
+  // then re-use the one from the head we computed first.
   if (!hm.empty() && !hm.begin()->second.HadHeadSensitiveCondition) {
-    return &hm.begin()->second;
+    head = hm.begin()->first;
   }
 
   cmOptionalLinkInterface& iface = hm[head];
+  if (secondPass) {
+    iface = cmOptionalLinkInterface();
+  }
   if (!iface.LibrariesDone) {
     iface.LibrariesDone = true;
     this->ComputeLinkInterfaceLibraries(config, iface, head,
@@ -6875,9 +6874,9 @@ const cmLinkInterfaceLibraries* cmGeneratorTarget::GetLinkInterfaceLibraries(
        : this->GetHeadToLinkInterfaceMap(config));
 
   // If the link interface does not depend on the head target
-  // then return the one we computed first.
+  // then re-use the one from the head we computed first.
   if (!hm.empty() && !hm.begin()->second.HadHeadSensitiveCondition) {
-    return &hm.begin()->second;
+    head = hm.begin()->first;
   }
 
   cmOptionalLinkInterface& iface = hm[head];
@@ -7381,17 +7380,16 @@ const cmLinkInterface* cmGeneratorTarget::GetImportLinkInterface(
        ? this->GetHeadToLinkInterfaceUsageRequirementsMap(config)
        : this->GetHeadToLinkInterfaceMap(config));
 
-  if (secondPass) {
-    hm.erase(headTarget);
-  }
-
   // If the link interface does not depend on the head target
-  // then return the one we computed first.
+  // then re-use the one from the head we computed first.
   if (!hm.empty() && !hm.begin()->second.HadHeadSensitiveCondition) {
-    return &hm.begin()->second;
+    headTarget = hm.begin()->first;
   }
 
   cmOptionalLinkInterface& iface = hm[headTarget];
+  if (secondPass) {
+    iface = cmOptionalLinkInterface();
+  }
   if (!iface.AllDone) {
     iface.AllDone = true;
     iface.LibrariesDone = true;
@@ -7905,9 +7903,9 @@ cmGeneratorTarget::GetLinkImplementationLibrariesInternal(
     this->LinkImplMap[cmSystemTools::UpperCase(config)];
 
   // If the link implementation does not depend on the head target
-  // then return the one we computed first.
+  // then re-use the one from the head we computed first.
   if (!hm.empty() && !hm.begin()->second.HadHeadSensitiveCondition) {
-    return &hm.begin()->second;
+    head = hm.begin()->first;
   }
 
   cmOptionalLinkImplementation& impl = hm[head];
-- 
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