LT-22816: Rebuild native objects when an included header changes

Bld/Write-NmakeHeaderDependencies.ps1

@@ -0,0 +1,173 @@
+<#
+.SYNOPSIS
+	Writes the nmake header dependencies for one native build product.
+
+.DESCRIPTION
+	Every compile rule in Bld/_rule.mak writes a cl /sourceDependencies sidecar
+	(<object>.source-dependencies.json) next to its object file. This script reads
+	those sidecars for one product and writes header-dependencies.mak, which the
+	end of Bld/_targ.mak includes, so nmake rebuilds an object whenever a header it
+	includes changes. nmake still makes every up-to-date decision; this script only
+	supplies the edges.
+
+	An object with no sidecar (compiled before header tracking existed, or its
+	sidecar was deleted) depends on a target that is always out of date, so it is
+	rebuilt once and gains a sidecar. A missing precompiled header does the same
+	for the objects that produce and use it.
+
+.PARAMETER RepositoryRoot
+	Repository root. Headers outside it (SDK, toolset) are not tracked.
+
+.PARAMETER IntermediateDirectory
+	The product's intermediate directory, $(INT_DIR). The include file is written
+	here.
+#>
+param(
+	[Parameter(Mandatory = $true)]
+	[string] $RepositoryRoot,
+	[Parameter(Mandatory = $true)]
+	[string] $IntermediateDirectory
+)
+
+Set-StrictMode -Version Latest
+$ErrorActionPreference = 'Stop'
+
+$sidecarSuffix = '.source-dependencies.json'
+$forceTarget = 'header-dependencies-force'
+$repositoryPrefix = [IO.Path]::GetFullPath($RepositoryRoot).TrimEnd('\', '/') + '\'
+$intermediateDirectory = [IO.Path]::GetFullPath($IntermediateDirectory)
+
+if (-not [IO.Directory]::Exists($intermediateDirectory)) {
+	exit 0
+}
+
+# nmake expands $ as a macro even inside quotes, so it is doubled. A # cannot be
+# escaped inside a quoted name, so such a path fails the build rather than
+# producing an edge to a file that does not exist.
+function ConvertTo-NmakePath([string] $path) {
+	if ($path.Contains('#')) {
+		throw "Header dependency path contains '#', which nmake cannot quote: $path"
+	}
+	return '"' + $path.Replace('$', '$$') + '"'
+}
+
+# Returns the repository headers and PCH the sidecar records, and whether its PCH
+# is missing. Deleted or renamed headers are dropped so they never become targets
+# nmake cannot make.
+function Get-TrackedFile([string] $sidecarPath) {
+	$result = @{
+		Paths = New-Object 'System.Collections.Generic.List[string]'
+		MissingPch = $false
+	}
+	$data = ([IO.File]::ReadAllText($sidecarPath) | ConvertFrom-Json).Data
+	$candidates = New-Object 'System.Collections.Generic.List[object]'
+	$includes = $data.PSObject.Properties['Includes']
+	if ($null -ne $includes) {
+		foreach ($include in @($includes.Value)) {
+			$candidates.Add(@{ Value = $include; IsPch = $false })
+		}
+	}
+	$pch = $data.PSObject.Properties['PCH']
+	if ($null -ne $pch -and $null -ne $pch.Value) {
+		$candidates.Add(@{ Value = $pch.Value; IsPch = $true })
+	}
+	foreach ($candidate in $candidates) {
+		$value = $candidate.Value
+		$path = $null
+		if ($value -is [string]) {
+			$path = $value
+		}
+		elseif ($null -ne $value -and $null -ne $value.PSObject.Properties['Path']) {
+			$path = [string]$value.Path
+		}
+		if ([string]::IsNullOrWhiteSpace($path)) {
+			continue
+		}
+		$path = [IO.Path]::GetFullPath($path)
+		if (-not $path.StartsWith($repositoryPrefix, [StringComparison]::OrdinalIgnoreCase)) {
+			continue
+		}
+		if ([IO.File]::Exists($path)) {
+			$result.Paths.Add($path)
+		}
+		elseif ($candidate.IsPch) {
+			$result.MissingPch = $true
+		}
+	}
+	return $result
+}
+
+$edges = New-Object 'System.Collections.Generic.List[string]'
+$forced = New-Object 'System.Collections.Generic.SortedSet[string]' ([StringComparer]::OrdinalIgnoreCase)
+$pchMissing = $false
+$objects = [IO.Directory]::GetFiles($intermediateDirectory, '*.obj', [IO.SearchOption]::AllDirectories)
+[Array]::Sort($objects, [StringComparer]::OrdinalIgnoreCase)
+foreach ($object in $objects) {
+	$sidecar = $object + $sidecarSuffix
+	if (-not [IO.File]::Exists($sidecar)) {
+		[void]$forced.Add($object)
+		continue
+	}
+	$tracked = Get-TrackedFile $sidecar
+	if ($tracked.MissingPch) {
+		[void]$forced.Add($object)
+		$pchMissing = $true
+	}
+	$tracked.Paths.Sort([StringComparer]::OrdinalIgnoreCase)
+	$target = ConvertTo-NmakePath $object
+	foreach ($path in $tracked.Paths) {
+		$edges.Add($target + ' : ' + (ConvertTo-NmakePath $path))
+	}
+}
+# A missing PCH is only recreated when its /Yc producer compiles again.
+if ($pchMissing) {
+	foreach ($object in $objects) {
+		if ([IO.Path]::GetFileName([IO.Path]::GetDirectoryName($object)) -ieq 'genpch') {
+			[void]$forced.Add($object)
+		}
+	}
+}
+
+$lines = New-Object 'System.Collections.Generic.List[string]'
+$lines.AddRange($edges)
+foreach ($object in $forced) {
+	$lines.Add((ConvertTo-NmakePath $object) + ' : ' + $forceTarget)
+}
+if ($forced.Count -gt 0) {
+	$lines.Add($forceTarget + ' :')
+	$lines.Add("`t@rem")
+}
+
+$content = [string]::Join("`r`n", $lines.ToArray())
+if ($content.Length -gt 0) {
+	$content += "`r`n"
+}
+$makeFile = Join-Path $intermediateDirectory 'header-dependencies.mak'
+if ([IO.File]::Exists($makeFile) -and [IO.File]::ReadAllText($makeFile) -ceq $content) {
+	exit 0
+}
+
+# Write beside the target, then replace it, so nmake never reads a partial file.
+$temporaryFile = $makeFile + '.' + [Diagnostics.Process]::GetCurrentProcess().Id + '.tmp'
+try {
+	[IO.File]::WriteAllText($temporaryFile, $content, (New-Object System.Text.UTF8Encoding($false)))
+	$moved = $false
+	if (-not [IO.File]::Exists($makeFile)) {
+		try {
+			[IO.File]::Move($temporaryFile, $makeFile)
+			$moved = $true
+		}
+		catch [IO.IOException] {
+			# Another build created the file first; replace it below instead.
+		}
+	}
+	if (-not $moved) {
+		# Windows PowerShell passes $null to a string parameter as "", which Replace rejects.
+		[IO.File]::Replace($temporaryFile, $makeFile, [NullString]::Value)
+	}
+}
+finally {
+	if ([IO.File]::Exists($temporaryFile)) {
+		[IO.File]::Delete($temporaryFile)
+	}
+}