Ncnn: ios armv7 device crash

[sbsb99]

i use 20201208_0508315 release.

my code is

ncnn::Net aNet;
aNet.load_param(param_path.c_str());
aNet.load_model(model_path.c_str());

arm64 device(iPhone 7) work fine, but armv7 device(iPhone 4S) crash at load_model().
call stack is

thread #6, queue = 'com.testApp, stop reason = EXC_BAD_ACCESS (code=EXC_ARM_DA_ALIGN, address=0x169aca2c)
  * frame #0: 0x00e4c04c testApp`__kmp_hyper_barrier_release(barrier_type, kmp_info*, int, int, int) + 460
    frame #1: 0x00e4d7b4 testApp`__kmp_fork_barrier(int, int) + 210
    frame #2: 0x00e3e3dc testApp`__kmp_fork_call + 4784
    frame #3: 0x00e39b9e testApp`__kmpc_fork_call + 62
    frame #4: 0x00c9efbe testApp`ncnn::conv3x3s1_winograd64_transform_kernel_pack4_neon(ncnn::Mat const&, ncnn::Mat&, int, int) + 194
    frame #5: 0x00c9cc78 testApp`ncnn::Convolution_arm::create_pipeline(ncnn::Option const&) + 5184
    frame #6: 0x00c8eda4 testApp`ncnn::Net::load_model(ncnn::DataReader const&) + 294
    frame #7: 0x00c8eeb2 testApp`ncnn::Net::load_model(char const*) + 48

thread #7
   frame #0: 0x00e7578e testApp`__kmp_suspend_64 + 58
    frame #1: 0x00e6eb64 testApp`kmp_flag_64::wait(kmp_info*, int) + 704
    frame #2: 0x00e6cecc testApp`__kmp_hyper_barrier_release(barrier_type, kmp_info*, int, int, int) + 76
    frame #3: 0x00e6e7b4 testApp`__kmp_fork_barrier(int, int) + 210
    frame #4: 0x00e60938 testApp`__kmp_launch_thread + 146
    frame #5: 0x00e74a18 testApp`__kmp_launch_worker(void*) + 66
    frame #6: 0x37c08872 libsystem_pthread.dylib`<redacted> + 138
    frame #7: 0x37c087e6 libsystem_pthread.dylib`_pthread_start + 110
    frame #8: 0x37c06740 libsystem_pthread.dylib`thread_start + 8

[nihui]

hi, please provide your model param file for reproducing the issue

[sbsb99]

I also reproduced with example param and model files.

• https://github.com/Tencent/ncnn/blob/master/examples/squeezenet_v1.1.param
• https://github.com/Tencent/ncnn/blob/master/examples/squeezenet_v1.1.bin

I tested it with previous releases. (Imported ncnn.framework and openmp.framework for each package.)

• 20201218_5650b77 => crash
• 20201208_0508315 => crash
• 20200916_b766c8c => crash
• 20200727_bedf00a => crash
• 20200616_622879a => crash
• 20200413_5580da4 => crash
• 20200226_57bedd5 => work fine

[sbsb99]

20210124_5e4ea0b => crash

[nihui]

I suspect there is some regression bug during the openmp upgrading from 7.0.0 to 11.0.0
Try linking with openmp 20200226 with the latest ncnn and see if it makes any difference