macOS 10.14+ seek 或重新播放时 PlayerThread 崩溃

[pzhlkj6612]

环境

• macOS 10.14 (18A391) / 10.15.3 (19D76)
• VMware Workstation 15.5.0 build-14665864 / 15.5.1 build-15018445
• Unlocker 3.0.3 * from paolo-projects
• FFmpeg 4.2.2
• SDL 2.0.10

seek 时崩溃

报告（部分）：

...

Crashed Thread:        11  PlayThread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000018
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Segmentation fault: 11
Termination Reason:    Namespace SIGNAL, Code 0xb
Terminating Process:   exc handler [12053]

...

Thread 11 Crashed:: PlayThread
0   com.yourcompany.Beslyric-for-X	0x0000000107496a99 packet_queue_flush(PacketQueue*) + 73 (musicPlayer.cpp:120)
1   com.yourcompany.Beslyric-for-X	0x0000000107498847 PlayThread::generateAudioDataLoop() + 1159 (musicPlayer.cpp:605)
2   com.yourcompany.Beslyric-for-X	0x0000000107497214 PlayThread::run() + 196 (musicPlayer.cpp:279)
3   org.qt-project.QtCore         	0x000000010a426fd3 0x10a405000 + 139219
4   libsystem_pthread.dylib       	0x00007fff6a2bf33d _pthread_body + 126
5   libsystem_pthread.dylib       	0x00007fff6a2c22a7 _pthread_start + 70
6   libsystem_pthread.dylib       	0x00007fff6a2be425 thread_start + 13

...

重新播放时崩溃

...

Crashed Thread:        4  PlayThread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000018
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Segmentation fault: 11
Termination Reason:    Namespace SIGNAL, Code 0xb
Terminating Process:   exc handler [622]

...

Thread 4 Crashed:: PlayThread
0   com.yourcompany.Beslyric-for-X	0x000000010475d2b9 packet_queue_flush(PacketQueue*) + 73 (musicPlayer.cpp:120)
1   com.yourcompany.Beslyric-for-X	0x000000010475f74c PlayThread::clearContextAndCloseDevice() + 124 (musicPlayer.cpp:627)
2   com.yourcompany.Beslyric-for-X	0x000000010475eaa8 PlayThread::ReleaseAll() + 56 (musicPlayer.cpp:663)
3   com.yourcompany.Beslyric-for-X	0x000000010475d933 PlayThread::run() + 211 (musicPlayer.cpp:259)
4   org.qt-project.QtCore         	0x0000000107e7aba9 QThreadPrivate::start(void*) + 329
5   libsystem_pthread.dylib       	0x00007fff634a4e65 _pthread_start + 148
6   libsystem_pthread.dylib       	0x00007fff634a083b thread_start + 15

...

可能的解决方案

检查packet_queue_flush(PacketQueue *q)：

https://github.com/Beslyric-for-X/Beslyric-for-X/blob/0dee64a8834f1ba294b12f99fee97acc438ee500/Entities/MusicPlayer/musicPlayer.cpp#L113-L133

移除对pkt1->pkt.data的测试，或者增加对pkt1的空指针测试，问题不再出现：

-       if(pkt1->pkt.data != (uint8_t *)"FLUSH")
+       if(pkt1 != nullptr && pkt1->pkt.data != (uint8_t *)"FLUSH")
        {
            ;
        }

截至目前，这个问题在 Windows 7 / 10 、 Ubuntu 18.04 上都未曾出现过。

[pzhlkj6612]

MusicPlayer 似乎可根据 35.FFmpeg学习笔记 - ffplay源码解读3之读文件_周洪伟的博客-CSDN博客 、 ffplay播放控制代码分析_RonnieLiGe的专栏-CSDN博客 和 ffplay源码分析7-播放控制 - 叶余 - 博客园 中的内容进行调整。

实际上，读ffplay.c，也许就能解答很多问题了。