Darknet: Cannot build the project with LIBSO=1 in macOS

[tani]

I guess this issue relates #833 . In macOS, I couldn't build uselib and get this error.

g++ -std=c++11  -Wall -Wfatal-errors -Wno-unused-result -Wno-unknown-pragmas -Ofast -fPIC -o uselib src/yolo_console_dll.cpp -lm -pthread  -L ./ -l:darknet.so
src/yolo_console_dll.cpp:248:16: warning: unused variable 'save_output_videofile' [-Wunused-variable]
    bool const save_output_videofile = true;
               ^
src/yolo_console_dll.cpp:242:17: warning: unused variable 'thresh' [-Wunused-variable]
    float const thresh = (argc > 5) ? std::stof(argv[5]) : 0.20;
                ^
2 warnings generated.
ld: library not found for -l:darknet.so
clang: fatal error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [uselib] Error 1

My Makefile ($ head Makefile) is

GPU=0
CUDNN=0
CUDNN_HALF=0
OPENCV=0
AVX=0
OPENMP=0
LIBSO=1

# set GPU=1 and CUDNN=1 to speedup on GPU
# set CUDNN_HALF=1 to further speedup 3 x times (Mixed-precision using Tensor Cores) on GPU Tesla V100, Titan V, DGX-2

The version of GCC which is a wrapper of LLVM is

Configured with: --prefix=/Library/Developer/CommandLineTools/usr --with-gxx-include-dir=/Library/Developer/CommandLineTools/SDKs/MacOSX10.14.sdk/usr/include/c++/4.2.1
Apple LLVM version 10.0.0 (clang-1000.10.44.2)
Target: x86_64-apple-darwin18.0.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

And we can build with changing LIBNAMESO=darknet.so to LIBNAMESO=libdarknet.so like #833 .
Is it a LLVM's error? If it isn't, would you like to change the value of LIBNAMESO?

And it's off-topic, I'd like to This API in macOS and Linux. Can I build dll with This Makefile?

[AlexeyAB]

• If you use LIBNAMESO=darknet.so then will be created darknet.so file or libdarknet.so file?

• Try to leave LIBNAMESO=darknet.so
  and change -l:$(LIBNAMESO) to darknet.so here https://github.com/AlexeyAB/darknet/blob/7762372e5bba9e9411ee12d535b578159ca9043f/Makefile#L126

More info: https://stackoverflow.com/questions/1305266/how-to-link-to-a-shared-library-without-lib-prefix-in-a-different-directory

[tani]

Ah, I can build with your way, I changed like this.

diff --git a/Makefile b/Makefile
index 10cee6d..6726909 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@ CUDNN_HALF=0
 OPENCV=0
 AVX=0
 OPENMP=0
-LIBSO=0
+LIBSO=1

 # set GPU=1 and CUDNN=1 to speedup on GPU
 # set CUDNN_HALF=1 to further speedup 3 x times (Mixed-precision using Tensor Cores) on GPU Tesla V100, Titan V, DGX-2
@@ -123,7 +123,7 @@ $(LIBNAMESO): $(OBJS) src/yolo_v2_class.hpp src/yolo_v2_class.cpp
    $(CPP) -shared -std=c++11 -fvisibility=hidden -DYOLODLL_EXPORTS $(COMMON) $(CFLAGS) $(OBJS) src/yolo_v2_class.cpp -o $@ $(LDFLAGS)

 $(APPNAMESO): $(LIBNAMESO) src/yolo_v2_class.hpp src/yolo_console_dll.cpp
-   $(CPP) -std=c++11 $(COMMON) $(CFLAGS) -o $@ src/yolo_console_dll.cpp $(LDFLAGS) -L ./ -l:$(LIBNAMESO)
+   $(CPP) -std=c++11 $(COMMON) $(CFLAGS) -o $@ src/yolo_console_dll.cpp $(LDFLAGS) -L ./ darknet.so
 endif

 $(EXEC): $(OBJS)

Can I propose you this change as a pull request?

[tani]

Thank you for updating your project, for this issue.

[AlexeyAB]

Yes, I added commit with this fix.

[ianshmean]

This issue doesn't seem fixed in master. The suggested line to change above still exist as before, and causes the same error on MacOS

https://github.com/AlexeyAB/darknet/blob/7a854302efb7adba80d5e8a747ad5e5ec384a226/Makefile#L131-L133

Changing this line to the following removes the error (but I have downstream errors in the package I'm developing linked to the .so file not being dylib compliant, which I'm trying to figure out.. which may be a different issue)

$(CPP) -std=c++11 $(COMMON) $(CFLAGS) -o $@ src/yolo_console_dll.cpp $(LDFLAGS) -L ./ $(LIBNAMESO)

[AlexeyAB]

@ianshmean

Currently LIBNAMESO is changed from darknet.so to libdarknet.so https://github.com/AlexeyAB/darknet/blob/7a854302efb7adba80d5e8a747ad5e5ec384a226/Makefile#L50
so it should work on MacOS.

Also you can try to use Cmake that makes it work successfully on any MacOS, Ubuntu and Windows:

• https://travis-ci.org/AlexeyAB/darknet/builds/505504584?utm_source=github_status&utm_medium=notification
• https://ci.appveyor.com/project/AlexeyAB/darknet/builds/23027869

[ianshmean]

With the make process on master I see:

ld: library not found for -l:libdarknet.so

so the change to libdarknet.so didn't seem to fix it for me. However the change I did above did fix it, and I'm now functional.

On a side note, for a MacOS build, the libdarknet extension should be .dylib not .so to play nicely with other packages that check for lib file types against standard practice, so I wonder whether that would be something to point out in the file, incase the user doesn't know that nuance. (that was tripping me up)

I haven't tried Cmake, would that fix that .dylib issue?

[AlexeyAB]

@ianshmean

I haven't tried Cmake, would that fix that .dylib issue?

I didn't try it on MacOS. If you can try it, we will think about fix it.