FindBLAS with static OpenBLAS 1.10.3
Using CMake 3.6.1, and a OpenBLAS 1.10.3 (build with `NO_SHARED=1`), FindBLAS fails.
It is included with:
```
set(BLA_STATIC on)
set(BLA_VENDOR OpenBLAS)
find_package(BLAS REQUIRED)
if (BLAS_FOUND)
include_directories(${BLAS_INCLUDE_DIRS})
target_link_libraries(classification ${BLAS_LIBRARIES})
endif()
```
Fails with:
```
-- Looking for sgemm_
-- Looking for sgemm_ - not found
CMake Error at /usr/local/share/cmake-3.6/Modules/FindBLAS.cmake:693 (message):
A required library with BLAS API not found. Please specify library
location.
```
The log from CMakeError.log shows that it fails to find pthreads:
```
Determining if the function sgemm_ exists failed with the following output:
Change Dir: <some_path>/build/CMakeFiles/CMakeTmp
Run Build Command:"/usr/bin/make" "cmTC_5a823/fast"
/usr/bin/make -f CMakeFiles/cmTC_5a823.dir/build.make CMakeFiles/cmTC_5a823.dir/build
make[1]: Entering directory `<some_path>/build/CMakeFiles/CMakeTmp'
Building C object CMakeFiles/cmTC_5a823.dir/CheckFunctionExists.c.o
/usr/bin/cc -DCHECK_FUNCTION_EXISTS=sgemm_ -o CMakeFiles/cmTC_5a823.dir/CheckFunctionExists.c.o -c /usr/local/share/cmake-3.6/Modules/CheckFunctionExists.c
Linking C executable cmTC_5a823
/usr/local/bin/cmake -E cmake_link_script CMakeFiles/cmTC_5a823.dir/link.txt --verbose=1
/usr/bin/cc -DCHECK_FUNCTION_EXISTS=sgemm_ CMakeFiles/cmTC_5a823.dir/CheckFunctionExists.c.o -o cmTC_5a823 <some_path>/lib/libopenblas.a
<some_path>/lib/libopenblas.a(memory.o): In function `openblas_fork_handler':
memory.c:(.text+0x1a0): undefined reference to `pthread_atfork'
<some_path>/lib/libopenblas.a(blas_server.o): In function `blas_thread_init':
blas_server.c:(.text+0x3b4): undefined reference to `pthread_create'
<some_path>/lib/libopenblas.a(blas_server.o): In function `goto_set_num_threads':
blas_server.c:(.text+0x85a): undefined reference to `pthread_create'
<some_path>/lib/libopenblas.a(blas_server.o): In function `blas_thread_shutdown_':
blas_server.c:(.text+0xa83): undefined reference to `pthread_join'
collect2: error: ld returned 1 exit status
make[1]: *** [cmTC_5a823] Error 1
make[1]: Leaving directory `<some_path>/build/CMakeFiles/CMakeTmp'
make: *** [cmTC_5a823/fast] Error 2
```
I resolved this on my machine by setting "pthreads" as the threading type at https://gitlab.kitware.com/cmake/cmake/blob/master/Modules/FindBLAS.cmake#L179. I see that no other items currently use this, did I build openblas particularly? After changing, that block of code read:
```
if (BLA_VENDOR STREQUAL "OpenBLAS" OR BLA_VENDOR STREQUAL "All")
if(NOT BLAS_LIBRARIES)
# OpenBLAS (http://www.openblas.net)
check_fortran_libraries(
BLAS_LIBRARIES
BLAS
sgemm
""
"openblas"
"pthreads"
)
message("BLAS_LIBRARIES:" ${BLAS_LIBRARIES})
endif()
endif ()
```
issue