WaveFile: don't assert-crash when the wav file couldn't be opened

__StartLogAudio ignored WaveFileWriter::Start()'s return value and set m_logAudio
either way, so a wav file that couldn't be opened - read-only or full audio
directory, most likely - left every subsequent mixed block calling
AddStereoSamples on a closed file. That opens with _assert_msg_(file, ...).

Also other minor fixes.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01GZq8ZtJmFY7bkX5FVkr3P9

Core/HLE/__sceAudio.cpp

@@ -477,8 +477,15 @@ void __AudioUpdate(bool resetRecording) {
 #ifndef MOBILE_DEVICE
 void __StartLogAudio(const Path& filename) {
 	if (!m_logAudio) {
+		if (!g_wave_writer.Start(filename, 44100)) {
+			// Start() logs the reason. Leave m_logAudio false, or every mixed block from here on
+			// would hand samples to a closed file - and turn the setting off too, since otherwise
+			// the caller below retries this (creating the file, opening it) once per block.
+			ERROR_LOG(Log::sceAudio, "Failed to start audio logging, disabling it");
+			g_Config.bDumpAudio = false;
+			return;
+		}
 		m_logAudio = true;
-		g_wave_writer.Start(filename, 44100);
 		g_wave_writer.SetSkipSilence(false);
 		NOTICE_LOG(Log::sceAudio, "Starting Audio logging");
 	} else {

Core/WaveFile.cpp

@@ -6,8 +6,6 @@
 #include "Common/Log.h"
 #include "Core/Config.h"
 
-constexpr size_t WaveFileWriter::BUFFER_SIZE;
-
 WaveFileWriter::WaveFileWriter() {}
 
 WaveFileWriter::~WaveFileWriter()
@@ -78,10 +76,15 @@ void WaveFileWriter::Write4(const char* ptr)
 	file.WriteBytes(ptr, 4);
 }
 
+// count is the number of stereo frames, so 4 bytes each.
 void WaveFileWriter::AddStereoSamples(const short* sample_data, uint32_t count)
 {
-	_assert_msg_(file, "WaveFileWriter - file not open.");
-	_assert_msg_(count <= BUFFER_SIZE * 2, "WaveFileWriter - buffer too small (count = %u).", count);
+	if (!file) {
+		// Callers are supposed to check that Start() succeeded, but this used to assert - which
+		// isn't compiled out in release builds, so a file we couldn't open crashed the emulator.
+		ERROR_LOG(Log::System, "WaveFileWriter - file not open.");
+		return;
+	}
 
 	if (skip_silence)
 	{

Core/WaveFile.h

@@ -30,8 +30,6 @@ public:
 	void AddStereoSamples(const short* sample_data, uint32_t count);
 	uint32_t GetAudioSize() const { return audio_size; }
 private:
-	static constexpr size_t BUFFER_SIZE = 32 * 1024;
-
 	File::IOFile file;
 	bool skip_silence = false;
 	uint32_t audio_size = 0;