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audio: Tweak SDL_GetAudioDeviceName.

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- Add checks that ObtainPhysicalAudioDevice() was previously doing
  (is subsystem initialized, is device valid).
- Remove optimizations that copy string to stack to release device_hash_lock
  before SDL_GetPersistentString is called. Probably not necessary, and made
  the code more complex.
This commit is contained in:
Ryan C. Gordon
2025-04-24 22:17:13 -04:00
parent da3c864d4c
commit b28449a58c
1 changed files with 14 additions and 21 deletions
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35
src/audio/SDL_audio.c
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@@ -1502,31 +1502,24 @@ SDL_AudioDevice *SDL_FindPhysicalAudioDeviceByHandle(void *handle)
const char *SDL_GetAudioDeviceName(SDL_AudioDeviceID devid)
{
bool isstack = false;
char *string = NULL;
const char *result = NULL;
SDL_AudioDevice *device = NULL;
// This does not call ObtainPhysicalAudioDevice() because the device's name never changes, so
// it doesn't have to lock the whole device. However, just to make sure the device pointer itself
// remains valid (in case the device is unplugged at the wrong moment), we hold the
// device_hash_lock while we copy the string.
SDL_LockRWLockForReading(current_audio.device_hash_lock);
SDL_FindInHashTable(current_audio.device_hash, (const void *) (uintptr_t) devid, (const void **) &device);
if (device) {
const size_t slen = SDL_strlen(device->name) + 1;
// SDL_GetPersistentString might _also_ makes a copy, but it might also create a TLS slot and a hashtable before doing a lookup, malloc+copy, and insert.
// So just try to tuck this into a little stack space while we're holding device_hash_lock.
string = SDL_small_alloc(char, slen, &isstack);
if (string) {
SDL_strlcpy(string, device->name, slen);
if (!SDL_GetCurrentAudioDriver()) {
SDL_SetError("Audio subsystem is not initialized");
} else {
// This does not call ObtainPhysicalAudioDevice() because the device's name never changes, so
// it doesn't have to lock the whole device. However, just to make sure the device pointer itself
// remains valid (in case the device is unplugged at the wrong moment), we hold the
// device_hash_lock while we copy the string.
SDL_LockRWLockForReading(current_audio.device_hash_lock);
SDL_FindInHashTable(current_audio.device_hash, (const void *) (uintptr_t) devid, (const void **) &device);
if (!device) {
SDL_SetError("Invalid audio device instance ID");
} else {
result = SDL_GetPersistentString(device->name);
}
}
SDL_UnlockRWLock(current_audio.device_hash_lock);
if (string) {
result = SDL_GetPersistentString(string);
SDL_small_free(string, isstack);
SDL_UnlockRWLock(current_audio.device_hash_lock);
}
return result;