Fixed ObjFileIsUptodate checks in library discovery.

During the library detection phase, we do not have objects files yet,
the only thing that we should check is if the dependency file is
up-to-date.

In this commit we let GCC create a dep file during the library discovery
phase.

We must ensure that the build-path folder exists otherwise the compiler
will not be able to create the dep file.

Author: cmaglie

internal/arduino/builder/internal/detector/detector.go

@@ -275,6 +275,7 @@ func (l *SketchLibrariesDetector) findIncludes(
 		if entry.Compile != nil && entry.CompileTask != nil {
 			upToDate, _ := entry.Compile.ObjFileIsUpToDate()
 			if !upToDate {
+				_ = entry.Compile.PrepareBuildPath()
 				l.preRunner.Enqueue(entry.CompileTask)
 			}
 		}
@@ -360,7 +361,8 @@ func (l *SketchLibrariesDetector) gccPreprocessTask(sourceFile *sourceFile, buil
 		includeFolders = append(includeFolders, extraInclude)
 	}
 
-	return preprocessor.GCC(sourceFile.SourcePath, paths.NullPath(), includeFolders, buildProperties, nil)
+	_ = sourceFile.PrepareBuildPath()
+	return preprocessor.GCC(sourceFile.SourcePath, paths.NullPath(), includeFolders, buildProperties, sourceFile.DepfilePath)
 }
 
 func (l *SketchLibrariesDetector) findMissingIncludesInCompilationUnit(
@@ -533,8 +535,7 @@ func (l *SketchLibrariesDetector) makeSourceFile(sourceRoot, buildRoot, sourceFi
 	}
 	res := &sourceFile{
 		SourcePath:       sourceRoot.JoinPath(sourceFilePath),
-		ObjectPath:       buildRoot.Join(sourceFilePath.String() + ".o"),
-		DepfilePath:      buildRoot.Join(sourceFilePath.String() + ".d"),
+		DepfilePath:      buildRoot.Join(fmt.Sprintf("%s.libsdetect.d", sourceFilePath)),
 		ExtraIncludePath: extraIncludePath,
 	}
 	return res, nil

internal/arduino/builder/internal/detector/source_file.go

@@ -19,17 +19,17 @@ import (
 	"fmt"
 	"slices"
 
-	"github.com/arduino/arduino-cli/internal/arduino/builder/internal/utils"
+	"os"
+
+	"github.com/arduino/arduino-cli/internal/arduino/builder/cpp"
 	"github.com/arduino/go-paths-helper"
+	"github.com/sirupsen/logrus"
 )
 
 type sourceFile struct {
 	// SourcePath is the path to the source file
 	SourcePath *paths.Path `json:"source_path"`
 
-	// ObjectPath is the path to the object file that will be generated
-	ObjectPath *paths.Path `json:"object_path"`
-
 	// DepfilePath is the path to the dependency file that will be generated
 	DepfilePath *paths.Path `json:"depfile_path"`
 
@@ -41,22 +41,82 @@ type sourceFile struct {
 }
 
 func (f *sourceFile) String() string {
-	return fmt.Sprintf("SourcePath:%s SourceRoot:%s BuildRoot:%s ExtraInclude:%s",
-		f.SourcePath, f.ObjectPath, f.DepfilePath, f.ExtraIncludePath)
+	return fmt.Sprintf("%s -> dep:%s (ExtraInclude:%s)",
+		f.SourcePath, f.DepfilePath, f.ExtraIncludePath)
 }
 
 // Equals checks if a sourceFile is equal to another.
 func (f *sourceFile) Equals(g *sourceFile) bool {
 	return f.SourcePath.EqualsTo(g.SourcePath) &&
-		f.ObjectPath.EqualsTo(g.ObjectPath) &&
 		f.DepfilePath.EqualsTo(g.DepfilePath) &&
 		((f.ExtraIncludePath == nil && g.ExtraIncludePath == nil) ||
 			(f.ExtraIncludePath != nil && g.ExtraIncludePath != nil && f.ExtraIncludePath.EqualsTo(g.ExtraIncludePath)))
 }
 
+// PrepareBuildPath ensures that the directory for the dependency file exists.
+func (f *sourceFile) PrepareBuildPath() error {
+	if f.DepfilePath != nil {
+		return f.DepfilePath.Parent().MkdirAll()
+	}
+	return nil
+}
+
 // ObjFileIsUpToDate checks if the compile object file is up to date.
 func (f *sourceFile) ObjFileIsUpToDate() (unchanged bool, err error) {
-	return utils.ObjFileIsUpToDate(f.SourcePath, f.ObjectPath, f.DepfilePath)
+	logrus.Debugf("Checking previous results for %v (dep = %v)", f.SourcePath, f.DepfilePath)
+	if f.DepfilePath == nil {
+		logrus.Debugf("  Object file or dependency file not provided")
+		return false, nil
+	}
+
+	sourceFile := f.SourcePath.Clean()
+	sourceFileStat, err := sourceFile.Stat()
+	if err != nil {
+		logrus.Debugf("  Could not stat source file: %s", err)
+		return false, err
+	}
+	dependencyFile := f.DepfilePath.Clean()
+	dependencyFileStat, err := dependencyFile.Stat()
+	if err != nil {
+		if os.IsNotExist(err) {
+			logrus.Debugf("  Dependency file not found: %v", dependencyFile)
+			return false, nil
+		}
+		logrus.Debugf("  Could not stat dependency file: %s", err)
+		return false, err
+	}
+	if sourceFileStat.ModTime().After(dependencyFileStat.ModTime()) {
+		logrus.Debugf("  %v newer than %v", sourceFile, dependencyFile)
+		return false, nil
+	}
+	deps, err := cpp.ReadDepFile(dependencyFile)
+	if err != nil {
+		logrus.Debugf("  Could not read dependency file: %s", dependencyFile)
+		return false, err
+	}
+	if len(deps.Dependencies) == 0 {
+		return true, nil
+	}
+	if deps.Dependencies[0] != sourceFile.String() {
+		logrus.Debugf("  Depfile is about different source file: %v (expected %v)", deps.Dependencies[0], sourceFile)
+		return false, nil
+	}
+	for _, dep := range deps.Dependencies[1:] {
+		depStat, err := os.Stat(dep)
+		if os.IsNotExist(err) {
+			logrus.Debugf("  Not found: %v", dep)
+			return false, nil
+		}
+		if err != nil {
+			logrus.WithError(err).Debugf("  Failed to read: %v", dep)
+			return false, nil
+		}
+		if depStat.ModTime().After(dependencyFileStat.ModTime()) {
+			logrus.Debugf("  %v newer than %v", dep, dependencyFile)
+			return false, nil
+		}
+	}
+	return true, nil
 }
 
 // uniqueSourceFileQueue is a queue of source files that does not allow duplicates.