fix: ErrorAlreadyExists 1832->183, wrap syscall errors, signal handling, mutex cleanup, log sync

.gitignore

@@ -1,2 +1,11 @@
 *.exe
 *.log
+*.exe~
+*.swp
+*.swo
+*~
+.env
+.idea/
+.vscode/
+.DS_Store
+Thumbs.db

README.md

@@ -1,9 +1,13 @@
 # autoPriority
 
-Automatically sets high CPU priority for memory-heavy processes.
+Automatically sets high CPU priority for processes exceeding a memory threshold.
+
+**Windows only.**
 
 ## Build
 
+Requires Go 1.26+.
+
 ```
 # Standard build (with console window)
 go build -o autopriority.exe .
@@ -20,18 +24,25 @@ autopriority [flags]
 
 | Flag        | Default       | Description                      |
 |-------------|---------------|----------------------------------|
-| `-mem`      | 536870912     | Memory threshold in bytes        |
+| `-mem`      | 536870912     | Memory threshold in bytes (512 MB) |
-| `-interval` | 1m0s          | Scan interval (min 10s)          |
+| `-interval` | 1 minute      | Scan interval (min 10s)          |
 | `-dry-run`  | false         | Log only, don't change priority  |
-| `-log`      | true          | Write `autopriority.log` to `%TEMP%` |
+
+Examples:
+
+```
+# Run with 1 GB memory threshold, scanning every 30 seconds
+autopriority -mem=1073741824 -interval=30s
+
+# Dry run — log decisions without changing anything
+autopriority -dry-run
+```
+
+Log is always written to `%TEMP%\autopriority.log`.
 
 ## Auto-start
 
-Place a shortcut to `autopriority.exe` in:
+Open **Win+R**, type `shell:startup`, and press Enter. Then place a shortcut to `autopriority.exe` in the folder that opens.
-
-```
-shell:startup
-```
 
 ## Dependencies
 

go.mod

@@ -1,3 +1,3 @@
 module autopriority
 
-go 1.25.0
+go 1.26

main.go

@@ -6,6 +6,7 @@ import (
 	"flag"
 	"fmt"
 	"os"
+	"os/signal"
 	"path/filepath"
 	"syscall"
 	"time"
@@ -20,7 +21,7 @@ const (
 	PriorityClassNormal             = 0x00000020
 	PriorityClassHigh               = 0x00000080
 	MessageBoxIconWarning           = 0x00000030
-	ErrorAlreadyExists              = 1832
+	ErrorAlreadyExists              = 183
 )
 
 type processEntry32 struct {
@@ -78,7 +79,7 @@ func closeH(h syscall.Handle) {
 func openProc(pid uint32, acc uint32) (syscall.Handle, error) {
 	r, _, e := procOpenProcess.Call(uintptr(acc), 0, uintptr(pid))
 	if r == 0 {
-		return 0, e
+		return 0, fmt.Errorf("OpenProcess(%d) failed: %w", pid, e)
 	}
 	return syscall.Handle(r), nil
 }
@@ -91,7 +92,7 @@ func setPrio(pid uint32, cls uint32) error {
 	defer closeH(h)
 	r, _, e := procSetPriority.Call(uintptr(h), uintptr(cls))
 	if r == 0 {
-		return e
+		return fmt.Errorf("SetPriorityClass(%d) failed: %w", pid, e)
 	}
 	return nil
 }
@@ -104,7 +105,7 @@ func curPrio(pid uint32) (uint32, error) {
 	defer closeH(h)
 	r, _, e := procGetPriority.Call(uintptr(h))
 	if r == 0 {
-		return 0, e
+		return 0, fmt.Errorf("GetPriorityClass(%d) failed: %w", pid, e)
 	}
 	return uint32(r), nil
 }
@@ -117,9 +118,10 @@ func rss(pid uint32) (uint64, error) {
 	defer closeH(h)
 
 	var m processMemoryCounters
+	m.CBM = uint32(unsafe.Sizeof(m))
 	r, _, e := procGetMemInfo.Call(uintptr(h), uintptr(unsafe.Pointer(&m)), uintptr(unsafe.Sizeof(m)))
 	if r == 0 {
-		return 0, e
+		return 0, fmt.Errorf("GetProcessMemoryInfo(%d) failed: %w", pid, e)
 	}
 	return uint64(m.WorkingSetSize), nil
 }
@@ -136,14 +138,14 @@ func utf16Trim(p []uint16) string {
 func allProcs() ([]processInfo, error) {
 	snap, _, e := procCreateSnap.Call(CreateToolhelp32SnapshotProcess, 0)
 	if snap == 0 {
-		return nil, e
+		return nil, fmt.Errorf("CreateToolhelp32Snapshot failed: %w", e)
 	}
 	defer closeH(syscall.Handle(snap))
 
 	pe := processEntry32{Size: uint32(unsafe.Sizeof(processEntry32{}))}
 	r, _, e := procProcess32First.Call(snap, uintptr(unsafe.Pointer(&pe)))
 	if r == 0 {
-		return nil, e
+		return nil, fmt.Errorf("Process32First failed: %w", e)
 	}
 
 	var out []processInfo
@@ -152,10 +154,15 @@ func allProcs() ([]processInfo, error) {
 		if name != "" {
 			out = append(out, processInfo{PID: pe.PID, Name: name})
 		}
+		pe.Size = uint32(unsafe.Sizeof(processEntry32{}))
 		r, _, e = procProcess32Next.Call(snap, uintptr(unsafe.Pointer(&pe)))
 		if r == 0 {
+			le, _, _ := procGetLastError.Call()
+			if le == 18 {
 				break
 			}
+			return nil, fmt.Errorf("Process32Next failed: %w", e)
+		}
 	}
 	return out, nil
 }
@@ -174,19 +181,22 @@ func prioName(c uint32) string {
 }
 
 func isAlive(pid uint32) bool {
-	h, _ := openProc(pid, ProcessQueryInformation)
+	h, err := openProc(pid, ProcessQueryInformation)
-	if h == 0 {
+	if err != nil || h == 0 {
 		return false
 	}
 	closeH(h)
 	return true
 }
 
-func ensureSingleInstance() {
+func ensureSingleInstance() syscall.Handle {
-	h, _, _ := procCreateMutex.Call(0, 0, uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr("Global\\autopriority_v1"))))
+	h, _, err := procCreateMutex.Call(0, 0, uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr("Global\\autopriority_v1"))))
+	if h == 0 {
+		fmt.Fprintf(os.Stderr, "autoPriority: failed to create mutex: %v\n", err)
+		os.Exit(1)
+	}
 	le, _, _ := procGetLastError.Call()
 	if uint32(le) == ErrorAlreadyExists {
-		closeH(syscall.Handle(h))
 		procMessageBox.Call(0,
 			uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr("autoPriority is already running."))),
 			uintptr(unsafe.Pointer(syscall.StringToUTF16Ptr("autoPriority"))),
@@ -194,6 +204,7 @@ func ensureSingleInstance() {
 		)
 		os.Exit(1)
 	}
+	return syscall.Handle(h)
 }
 
 func main() {
@@ -213,6 +224,7 @@ func main() {
 			os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0644)
 		if err == nil {
 			logFile = f
+			defer logFile.Close()
 		}
 	}
 
@@ -226,11 +238,13 @@ func main() {
 		}
 		fmt.Fprintf(logFile, "[%s] ", ts())
 		fmt.Fprintf(logFile, format+"\n", a...)
+		logFile.Sync()
 	}
 
 	logf("autoPriority started (mem=%d bytes, interval=%s, dry-run=%v)", *mem, *interval, *dryRun)
 
-	ensureSingleInstance()
+	mutex := ensureSingleInstance()
+	defer closeH(mutex)
 
 	if err := setPrio(uint32(os.Getpid()), PriorityClassIdle); err != nil {
 		logf("warning: could not set own priority to IDLE: %v", err)
@@ -240,9 +254,6 @@ func main() {
 
 	promoted := make(map[uint32]string)
 
-	if logFile != nil {
-		defer logFile.Close()
-	}
 	defer func() {
 		for pid, name := range promoted {
 			if err := setPrio(pid, PriorityClassNormal); err == nil {
@@ -256,6 +267,9 @@ func main() {
 	ticker := time.NewTicker(*interval)
 	defer ticker.Stop()
 
+	stop := make(chan os.Signal, 1)
+	signal.Notify(stop, os.Interrupt, syscall.SIGTERM)
+
 	scan := func() {
 		procs, err := allProcs()
 		if err != nil {
@@ -311,7 +325,18 @@ func main() {
 	}
 
 	scan()
-	for range ticker.C {
+	select {
+	case <-stop:
+		logf("received shutdown signal")
+	case <-ticker.C:
+		for {
 			scan()
+			select {
+			case <-stop:
+				logf("received shutdown signal")
+				return
+			case <-ticker.C:
+			}
+		}
 	}
 }