bound the configured audio buffer count

Buffers had a lower bound but no upper one, and it is allocated per speaking
user twice over: as a queue of decoded frames and as OpenAL playback
buffers. Each buffer holds up to one maximum sized frame, so a large value
multiplied by a populated channel is a substantial amount of memory.

Cap it, and reject the flag up front so the failure names the flag rather
than surfacing later as a dial error.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

gumble/gumble/config.go

@@ -38,6 +38,12 @@ type Config struct {
 	Buffers        int
 }
 
+// MaximumBuffers caps Config.Buffers. Each buffer holds up to one maximum
+// sized audio frame and is allocated per speaking user, so a large value
+// multiplied by a populated channel is a substantial amount of memory. A few
+// seconds of buffering is already far more than playback needs.
+const MaximumBuffers = 1024
+
 // NewConfig returns a new Config struct with default values set.
 func NewConfig() *Config {
 	return &Config{
@@ -64,6 +70,12 @@ func (c *Config) Validate() error {
 	if c.Buffers <= 0 {
 		return fmt.Errorf("gumble: Buffers must be positive")
 	}
+	// Buffers is allocated per speaking user, both as a queue of decoded
+	// frames and as OpenAL playback buffers, so an unbounded value multiplies
+	// straight into memory use as a channel fills up.
+	if c.Buffers > MaximumBuffers {
+		return fmt.Errorf("gumble: Buffers must be at most %d", MaximumBuffers)
+	}
 	return nil
 }
 

gumble/gumble/config_buffers_regression_test.go

@@ -0,0 +1,17 @@
+package gumble
+
+import "testing"
+
+// Regression: Buffers had no upper bound, but it is allocated per speaking
+// user both as a decoded-frame queue and as OpenAL playback buffers.
+func TestConfigRejectsOversizedBuffers(t *testing.T) {
+	config := NewConfig()
+	config.Buffers = MaximumBuffers + 1
+	if err := config.Validate(); err == nil {
+		t.Fatal("expected Buffers above the maximum to be rejected")
+	}
+	config.Buffers = MaximumBuffers
+	if err := config.Validate(); err != nil {
+		t.Fatalf("Buffers at the maximum should be accepted: %v", err)
+	}
+}

main.go

@@ -105,6 +105,10 @@ func main() {
 	if err != nil {
 		handle_raw_error(err)
 	}
+	if *buffers <= 0 || *buffers > gumble.MaximumBuffers {
+		handle_raw_error(fmt.Errorf("buffers must be between 1 and %d, got %d",
+			gumble.MaximumBuffers, *buffers))
+	}
 
 	// Set up logging
 	var level barnlog.Level