Rebuild native modules whose objects predate a header change

.github/workflows/CI.yml

@@ -65,6 +65,22 @@ jobs:
           Build\Agent\TokenHygiene.Tests.ps1
           if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
 
+      # The native build runs this staleness check under Windows PowerShell 5.1;
+      # FwBuildHelpers.psm1 itself loads under either engine.
+      - name: Native object staleness tests (PowerShell 7)
+        id: native-obj-staleness-tests-pwsh
+        shell: pwsh
+        run: |
+          Build/Agent/NativeObjStaleness.Tests.ps1
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+
+      - name: Native object staleness tests (Windows PowerShell 5.1)
+        id: native-obj-staleness-tests-winps
+        shell: powershell
+        run: |
+          Build\Agent\NativeObjStaleness.Tests.ps1
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+
       # -TokenHygiene fails CI on any hardcoded color/spacing literal in the Avalonia
       # surface (full-tree, no grandfathering -- unlike -CommentHygiene, which stays
       # advisory-only for humans here and only blocks agents locally).

Build/Agent/FwBuildHelpers.psm1

@@ -601,6 +601,148 @@ function Test-ViewsNativeArtifactsStale {
     return $latestSource -gt $oldestArtifact
 }
 
+function Get-NativeMakefileModules {
+	<#
+	.SYNOPSIS
+		Returns the nmake-built native modules with the directories whose headers each one
+		compiles against.
+	.DESCRIPTION
+		Each entry names the module's folder under Obj\<Configuration> and the repo-relative
+		directories, scanned without recursion, whose headers and makefiles feed its
+		objects. InputDirs covers the module makefile's UI include list, the folders its
+		sources reach through path-qualified includes, and the shared Include and Bld
+		folders. GeneratedDirs holds build-output folders as format strings taking the
+		configuration name; they exist only after a build. A directory missing from either
+		list leaves edits to its headers undetected for that module.
+	#>
+	$shared = @('Include', 'Include\unicode', 'Bld')
+	$generated = @('Output\{0}\Common')
+	return @(
+		[pscustomobject]@{
+			Name = 'Views'
+			InputDirs = @('Src\views', 'Src\views\lib', 'Src\Generic', 'Src\AppCore',
+				'Src\AppCore\Res', 'Src\Cellar', 'Src\DebugProcs', 'Src\Kernel',
+				'Lib\src\graphite2\include\graphite2') + $shared
+			GeneratedDirs = $generated
+		},
+		[pscustomobject]@{
+			Name = 'FwKernel'
+			InputDirs = @('Src\Kernel', 'Src\Generic', 'Src\AppCore', 'Src\DebugProcs',
+				'Src\Cellar') + $shared
+			GeneratedDirs = $generated
+		},
+		[pscustomobject]@{
+			Name = 'Generic'
+			InputDirs = @('Src\Generic') + $shared
+			GeneratedDirs = $generated
+		},
+		[pscustomobject]@{
+			Name = 'DebugProcs'
+			InputDirs = @('Src\DebugProcs') + $shared
+			GeneratedDirs = @()
+		}
+	)
+}
+
+function Remove-NativeObjDirsWithStaleInputs {
+	<#
+	.SYNOPSIS
+		Deletes a native module's intermediate folder when any header or makefile it builds
+		from is newer than its oldest object file.
+	.DESCRIPTION
+		The nmake rules in Bld rebuild an object only when its own source file changes, so a
+		header edit leaves every unedited file that includes it compiled against the old
+		header. When a class changes size that way, objects disagree about its layout and the
+		program corrupts memory at runtime. Deleting the module's Obj folder makes the next
+		native build compile all of it.
+
+		The check is coarse by design: any newer input rebuilds the whole module, including
+		files that never include the changed header.
+	.PARAMETER Modules
+		Module entries shaped like Get-NativeMakefileModules output. Defaults to that list.
+	.OUTPUTS
+		The names of the modules whose folders were removed.
+	#>
+	param(
+		[Parameter(Mandatory)][string]$RepoRoot,
+		[Parameter(Mandatory)][string]$Configuration,
+		[object[]]$Modules = (Get-NativeMakefileModules)
+	)
+
+	$inputPatterns = @('*.h', '*.hpp', '*.inl', '*.idh', '*.mak')
+	# bldinc.h holds only version stamps that local builds regenerate daily; a stale copy in
+	# an object changes no layout.
+	$ignoredInputs = @('bldinc.h')
+	$removed = New-Object System.Collections.Generic.List[string]
+
+	foreach ($module in $Modules) {
+		$objDir = Join-Path $RepoRoot (Join-Path "Obj\$Configuration" $module.Name)
+		if (-not (Test-Path -LiteralPath $objDir -PathType Container)) {
+			continue
+		}
+
+		$oldestObj = $null
+		foreach ($obj in ([System.IO.DirectoryInfo]$objDir).EnumerateFiles('*.obj', [System.IO.SearchOption]::AllDirectories)) {
+			if ($null -eq $oldestObj -or $obj.LastWriteTimeUtc -lt $oldestObj.LastWriteTimeUtc) {
+				$oldestObj = $obj
+			}
+		}
+		if ($null -eq $oldestObj) {
+			continue
+		}
+
+		$relativeDirs = @($module.InputDirs)
+		if ($module.PSObject.Properties['GeneratedDirs']) {
+			foreach ($format in $module.GeneratedDirs) {
+				$relativeDirs += ($format -f $Configuration)
+			}
+		}
+
+		$newestInput = $null
+		foreach ($relativeDir in $relativeDirs) {
+			$inputDir = Join-Path $RepoRoot $relativeDir
+			if (-not (Test-Path -LiteralPath $inputDir -PathType Container)) {
+				continue
+			}
+			foreach ($pattern in $inputPatterns) {
+				foreach ($file in ([System.IO.DirectoryInfo]$inputDir).EnumerateFiles($pattern, [System.IO.SearchOption]::TopDirectoryOnly)) {
+					if ($ignoredInputs -contains $file.Name) {
+						continue
+					}
+					if ($null -eq $newestInput -or $file.LastWriteTimeUtc -gt $newestInput.LastWriteTimeUtc) {
+						$newestInput = $file
+					}
+				}
+			}
+		}
+
+		if ($null -eq $newestInput -or $newestInput.LastWriteTimeUtc -le $oldestObj.LastWriteTimeUtc) {
+			continue
+		}
+
+		$inputLabel = $newestInput.FullName.Substring($RepoRoot.TrimEnd('\').Length + 1)
+		$objLabel = $oldestObj.FullName.Substring($objDir.TrimEnd('\').Length + 1)
+		Write-Host ("[INFO] {0}: {1} ({2:yyyy-MM-dd HH:mm}) is newer than {3} ({4:yyyy-MM-dd HH:mm}); removing Obj\{5}\{0} so it rebuilds completely." -f `
+			$module.Name, $inputLabel, $newestInput.LastWriteTime, $objLabel, $oldestObj.LastWriteTime, $Configuration) -ForegroundColor Yellow
+		$deleteErrors = @()
+		Remove-Item -LiteralPath $objDir -Recurse -Force -ErrorAction SilentlyContinue -ErrorVariable deleteErrors
+		if (Test-Path -LiteralPath $objDir) {
+			# The compiler's program-database server can hold a .pdb open between builds, and a
+			# leftover debug database does not affect what gets compiled.
+			$blocking = @(([System.IO.DirectoryInfo]$objDir).EnumerateFiles('*', [System.IO.SearchOption]::AllDirectories) |
+				Where-Object { $_.Extension -notin @('.pdb', '.idb') })
+			if ($blocking.Count -gt 0) {
+				$reason = if ($deleteErrors.Count -gt 0) { $deleteErrors[0].Exception.Message } else { 'unknown error' }
+				throw "Could not remove $($blocking[0].FullName) while clearing stale native objects: $reason"
+			}
+			Write-Host "[WARN] $($module.Name): a debug database in Obj\$Configuration\$($module.Name) is in use and was left in place; every object was removed, so the module still rebuilds completely." -ForegroundColor Yellow
+		}
+		$removed.Add($module.Name)
+	}
+
+	return ,$removed.ToArray()
+}
+
 function Set-TestAssertDialogEnvironment {
 	<#!
 	.SYNOPSIS
@@ -765,6 +907,8 @@ Export-ModuleMember -Function @(
 	'Get-NewestWriteTimeUtc',
 	'Get-OldestWriteTimeUtc',
 	'Test-ViewsNativeArtifactsStale',
+	'Get-NativeMakefileModules',
+	'Remove-NativeObjDirsWithStaleInputs',
 	'Set-TestAssertDialogEnvironment',
 	'Disable-CrashDialog',
 	'Get-UnitppSummary',