使用valgrind工具，发现在X86 Linux环境下存在内存泄露问题

[YaoQ]

使用该仓库，https://github.com/Hanson0910/MNNFaceDetect

基于MNN的人脸检测，在X86 Linux运行

使用valgrind分析，在X86 Linux环境下跑，mnn使用了2.0.2分支编译得到，同时尝试了master分支，还有mnn1.2.9分支，都检测存在内存泄露。

valgrind --tool=memcheck ./facedet --leak-check=full 
 
。。。
==35598== 
==35598== HEAP SUMMARY:
==35598==     in use at exit: 19,156,391 bytes in 15,501 blocks
==35598==   total heap usage: 36,103 allocs, 20,602 frees, 127,389,641 bytes allocated
==35598== 
==35598== LEAK SUMMARY:
==35598==    definitely lost: 144 bytes in 2 blocks  #确定存在内存泄露
==35598==    indirectly lost: 120,600 bytes in 5 blocks  #间接存在内存泄露
==35598==      possibly lost: 3,733,016 bytes in 292 blocks
==35598==    still reachable: 15,302,631 bytes in 15,202 blocks
==35598==         suppressed: 0 bytes in 0 blocks
==35598== Rerun with --leak-check=full to see details of leaked memory
==35598== 
==35598== For counts of detected and suppressed errors, rerun with: -v
==35598== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

[jxt1234]

看下是哪部分的内存泄露，valgrind 检查出来的有可能是初始的 register ，这个在实用中无影响

[wangzhaode]

这个内存泄露不影响