Ncnn: 为什么我拿ncnn编译出来的.a文件编译so的时候会报undefined reference to '__kmpc_fork_call'的错误

[zhangyanhbr]

你好，我想请问一下：
我拿ncnn编译出来的.a文件，用ndk-build编译.so的时候会报
undefined reference to '__kmpc_fork_call'
undefined reference to '__kmpc_for_static_init_4'
undefined reference to '__kmpc_for_static_fini'
undefined reference to '__kmpc_for_static_init_4'
layer/convolutiondepthwise.cpp:176: error:undefined reference to '__kmpc_for_static_init_8'

[nihui]

LOCAL_CFLAGS += -fopenmp
LOCAL_CPPFLAGS += -fopenmp
LOCAL_LDFLAGS += -fopenmp

参考 https://github.com/Tencent/ncnn/blob/master/examples/squeezencnn/jni/Android.mk

[zhangyanhbr]

你好，谢谢你的回复。但是我有点看不明白。您的意思是我少了这三行代码吗？我的Android.mk文件里有这三行代码的，是我少了什么库吗？

[zhangyanhbr]

你好，还有一个问题，我编译出来的libncnn.a有4560KB，而你们给出的libncnn.a不到1000KB，请问是什么原因呢？我是按照https://github.com/Tencent/ncnn/wiki/how-to-build这里面的步骤进行编译的。如果方便请回复一下。

[nihui]

android ndk 自带的cmake toolchain自动加上了 -g 编译，把 toolchain cmake 里的 -g 删掉重新编译一次就小了

[nihui]

android ndk 版本用 r15c 或者更新的

[suguliwei]

请问解决了吗？我也是碰到了同样的问题，build.sh发生了变化，现在用的是ndk自带的toolchain cmake，请问在编译的时候需要修改toolchain cmake里面的内容以支持openmp吗？

[zhangyanhbr]

我没有修改toolchain cmake里面的东西，我修改了.build.sh里面的东西就编译ok了。

[nihui]

新版使用了 android-ndk clang 编译器编译，openmp 运行时库对应于 libomp.a

[bobby-chiu]

@nihui, can be the ncnn static library libncnn.a compiled with APP_STL :=c++_static . The released version is compiled with gnustl_static?

[bobby-chiu]

@nihui, when i was packing libncnn.a into shared library with other libraries by settings stl as c++_static. it threw errors like:
/home/nihui/osd/ncnn/src/modelbin.cpp:(.text._ZNSt6vectorIhSaIhEE14_M_fill_insertEN9__gnu_cxx17__normal_iteratorIPhS1_EEmRKh[_ZNSt6vectorIhSaIhEE14_M_fill_insertEN9__gnu_cxx17__normal_iteratorIPhS1_EEmRKh]+0x1bc): undefined reference to `std::__throw_length_error(char const*)'.
This seems like gnustl dependencies

[bobby-chiu]

these errors were fixed by rebuilt ncnn library with c++_static stl.

[adong7639]

open Application.mk

APP_STL := stlport_static

APP_STL := gnustl_static

APP_ABI := armeabi armeabi-v7a

APP_ABI := armeabi-v7a
APP_PLATFORM := android-9

NDK_TOOLCHAIN_VERSION := 4.9

I solve this error like this:

NDK_TOOLCHAIN_VERSION := 4.9 >>>>> #NDK_TOOLCHAIN_VERSION := 4.9

[Victcode]

@nihui, 我用新版本出现类似的错误
Error:error: ld returned 1 exit status
Error:error: undefined reference to '__kmpc_fork_call'

我使用的是Android studio的cmake方式进行调用，请问如何解决，具体的指令我没有找到

[suesunna]

it has .so file after commend this line

NDK_TOOLCHAIN_VERSION := 4.9

[maxlchina]

but after commented NDK_TOOLCHAIN_VERSION := 4.9, the .so will be Invalid

[liujhjack]

你好，谢谢你的回复。但是我有点看不明白。您的意思是我少了这三行代码吗？我的Android.mk文件里有这三行代码的，是我少了什么库吗？

我这边也是添加了这三行code，还是不行，请问你是怎么解决的呢？

[liujhjack]

LOCAL_CFLAGS + = -fopenmp
LOCAL_CPPFLAGS + = -fopenmp
LOCAL_LDFLAGS + = -fopenmp

参考https://github.com/Tencent/ncnn/blob/master/examples/squeezencnn/jni/Android.mk

我添加了这个，还是报错，是需要openmp这个库吗？

[hdwf02]

我没有修改toolchain cmake里面的东西，我修改了.build.sh里面的东西就编译ok了。

你好，请问怎么修改呢，谢谢啊

[lvpchen]

these errors were fixed by rebuilt ncnn library with c++_static stl.

@bobby-chiu
hello, if i want to rebuilt ncnn library with c++_static stl, what i need to modify?
than you