find_package: Share package information among copies of package stack

Since commit ae373e93fb (install(PACKAGE_INFO): Add version and location
to package dependencies, 2025-07-31, v4.2.0-rc1~340^2) we add package
information to the current package's stack entry as it is discovered.
However, a nested package can cause the current package's stack entry to
be replaced by a copy with a new ordering index due to commit c6e6861e63
(install(EXPORT): Export find_dependency() calls, 2023-11-07,
v3.29.0-rc1~439^2~1).  Depending on whether imported targets were
created by the current package before finding the nested package, the
`CurrentPackageInfo` pointer is either invalidated, or left pointing at
only one of multiple copies.

Fix this by sharing a single instance of package information with all
copies of the current package's stack entry.  Keep a mutable pointer
to the current package's information only while it is still pending.
This also avoids the need to expose mutation from the package stack.

Add a test that exposes the previously-invalidated pointer to dynamic
analysis tools.

Fixes: #27730

Source/cmExportPackageInfoGenerator.cxx

@@ -298,7 +298,8 @@ bool cmExportPackageInfoGenerator::NoteLinkedTarget(
     auto pkgInfo = [](cmTarget* t) -> Package {
       cmFindPackageStack pkgStack = t->GetFindPackageStack();
       if (!pkgStack.Empty()) {
-        return std::make_pair(pkgStack.Top().Name, pkgStack.Top().PackageInfo);
+        return std::make_pair(pkgStack.Top().Name,
+                              *pkgStack.Top().PackageInfo);
       }
 
       cmPackageInformation package;

Source/cmFindPackageCommand.cxx

@@ -1218,13 +1218,15 @@ bool cmFindPackageCommand::FindPackage(
     }
   }
 
+  // Record package information discovered while it is loaded.
+  this->PackageInfo = std::make_shared<cmPackageInformation>();
+
   // RAII objects to ensure we leave this function with consistent state.
   FlushDebugBufferOnExit flushDebugBufferOnExit(*this);
   PushPopRootPathStack pushPopRootPathStack(*this);
   SetRestoreFindDefinitions setRestoreFindDefinitions(*this);
-  cmFindPackageStackRAII findPackageStackRAII(this->Makefile, this->Name);
-
-  findPackageStackRAII.BindTop(this->CurrentPackageInfo);
+  cmFindPackageStackRAII findPackageStackRAII(this->Makefile, this->Name,
+                                              this->PackageInfo);
 
   // See if we have been told to delegate to FetchContent or some other
   // redirected config package first. We have to check all names that
@@ -1272,8 +1274,8 @@ bool cmFindPackageCommand::FindPackage(
       this->Names.clear();
       this->Names.emplace_back(overrideName); // Force finding this one
       this->Variable = cmStrCat(this->Name, "_DIR");
-      this->CurrentPackageInfo->Directory = redirectsDir;
-      this->CurrentPackageInfo->Version = this->VersionFound;
+      this->PackageInfo->Directory = redirectsDir;
+      this->PackageInfo->Version = this->VersionFound;
       this->SetConfigDirCacheVariable(redirectsDir);
       break;
     }
@@ -1734,9 +1736,9 @@ bool cmFindPackageCommand::HandlePackageMode(
     }
 
     if (this->UseConfigFiles && found) {
-      this->CurrentPackageInfo->Directory =
+      this->PackageInfo->Directory =
         cmSystemTools::GetFilenamePath(this->FileFound);
-      this->CurrentPackageInfo->Version = this->VersionFound;
+      this->PackageInfo->Version = this->VersionFound;
     }
   }
 

Source/cmFindPackageCommand.h

@@ -285,7 +285,7 @@ private:
   std::set<std::string> OptionalComponents;
   std::set<std::string> RequiredTargets;
   std::string DebugBuffer;
-  cmPackageInformation* CurrentPackageInfo;
+  std::shared_ptr<cmPackageInformation> PackageInfo;
 
   enum class SearchResult
   {

Source/cmFindPackageStack.h

@@ -39,7 +39,7 @@ class cmFindPackageCall
 {
 public:
   std::string const Name;
-  cmPackageInformation PackageInfo;
+  std::shared_ptr<cmPackageInformation const> PackageInfo;
   unsigned int Index;
 };
 
@@ -50,19 +50,14 @@ public:
 class cmFindPackageStackRAII
 {
   cmMakefile* Makefile;
-  cmPackageInformation** Value = nullptr;
 
 public:
-  cmFindPackageStackRAII(cmMakefile* mf, std::string const& pkg);
+  cmFindPackageStackRAII(cmMakefile* mf, std::string const& pkg,
+                         std::shared_ptr<cmPackageInformation const> pkgInfo);
   ~cmFindPackageStackRAII();
 
   cmFindPackageStackRAII(cmFindPackageStackRAII const&) = delete;
   cmFindPackageStackRAII& operator=(cmFindPackageStackRAII const&) = delete;
-
-  /** Get a mutable pointer to the top of the stack.
-      The pointer is invalidated if BindTop is called again or when the
-      cmFindPackageStackRAII goes out of scope.  */
-  void BindTop(cmPackageInformation*& value);
 };
 
 /**

Source/cmMakefile.cxx

@@ -51,7 +51,6 @@
 #include "cmSourceFile.h"
 #include "cmSourceFileLocation.h"
 #include "cmSourceGroup.h"
-#include "cmStack.h"
 #include "cmState.h"
 #include "cmStateDirectory.h"
 #include "cmStateTypes.h"
@@ -4242,34 +4241,22 @@ cmMakefile::MacroPushPop::~MacroPushPop()
   this->Makefile->PopMacroScope(this->ReportError);
 }
 
-cmFindPackageStackRAII::cmFindPackageStackRAII(cmMakefile* mf,
-                                               std::string const& name)
+cmFindPackageStackRAII::cmFindPackageStackRAII(
+  cmMakefile* mf, std::string const& name,
+  std::shared_ptr<cmPackageInformation const> pkgInfo)
   : Makefile(mf)
 {
   this->Makefile->FindPackageStack =
     this->Makefile->FindPackageStack.Push(cmFindPackageCall{
       name,
-      cmPackageInformation(),
+      std::move(pkgInfo),
       this->Makefile->FindPackageStackNextIndex,
     });
   this->Makefile->FindPackageStackNextIndex++;
 }
 
-void cmFindPackageStackRAII::BindTop(cmPackageInformation*& value)
-{
-  if (this->Value) {
-    *this->Value = nullptr;
-  }
-  this->Value = &value;
-  value = &this->Makefile->FindPackageStack.cmStack::Top().PackageInfo;
-}
-
 cmFindPackageStackRAII::~cmFindPackageStackRAII()
 {
-  if (this->Value) {
-    *this->Value = nullptr;
-  }
-
   this->Makefile->FindPackageStackNextIndex =
     this->Makefile->FindPackageStack.Top().Index + 1;
   this->Makefile->FindPackageStack = this->Makefile->FindPackageStack.Pop();

Tests/RunCMake/find_package/NestedConfig.cmake

@@ -0,0 +1,3 @@
+cmake_policy(SET CMP0074 NEW)
+set(Outer_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/NestedConfig)
+find_package(Outer CONFIG)

Tests/RunCMake/find_package/NestedConfig/OuterConfig.cmake

@@ -0,0 +1 @@
+find_package(Inner CONFIG NO_DEFAULT_PATH)

Tests/RunCMake/find_package/RunCMakeTest.cmake

@@ -36,6 +36,7 @@ run_cmake(MissingConfigRequired)
 run_cmake(MissingConfigVersion)
 run_cmake(MixedModeOptions)
 run_cmake_with_options(ModuleModeDebugPkg --debug-find-pkg=Foo,Zot)
+run_cmake(NestedConfig)
 run_cmake(PackageRoot)
 run_cmake(PackageRootNestedConfig)
 run_cmake(PackageRootNestedModule)