[Buildroot] [PATCH] package/opencv3: fix CMAKE_CXX_FLAGS

[Vicente Olivert Riera]

Hello,

since this patch has been included [1] in Samuel's series I'm marking it
as superseded in patchwork.

1: https://patchwork.ozlabs.org/patch/682674/

Regards,

Vincent.

On 01/10/16 00:07, Samuel Martin wrote:
> Hi all,
> 
> On Fri, Sep 30, 2016 at 6:32 PM, Max Filippov <jcmvbkbc at gmail.com> wrote:
>> On Fri, Sep 30, 2016 at 1:10 AM, Thomas Petazzoni
>> <thomas.petazzoni at free-electrons.com> wrote:
>>> On Thu, 29 Sep 2016 09:14:41 -0700, Max Filippov wrote:
>>>>> There is something fishy going on here. Indeed,
>>>>> support/misc/toolchainfile.cmake.in contains:
>>>>>
>>>>>   set(CMAKE_CXX_FLAGS "@@TARGET_CXXFLAGS@@ ${CMAKE_CXX_FLAGS}" CACHE STRING "Buildroot CXXFLAGS")
>>>>>
>>>>> So it should normally always prefix CMAKE_CXX_FLAGS with
>>>>> TARGET_CXXFLAGS. Can you check the toolchain.cmake file that gets
>>>>> generated during your build? Does it contains the Xtensa specific
>>>>> CXXFLAGS ?
>>>>
>>>> Yes, it does.
>>>
>>> So if it does, why is your patch necessary? I'm not following here.
>>> Do you mean that the Xtensa-specific flags are present in the
>>> toolchain.cmake file, but are in the end not used during the build ?
>>
>> Right. The file
>>   host/usr/share/buildroot/toolchainfile.cmake
>> exists and contains the following (correct) lines:
>>
>> set(CMAKE_C_FLAGS "-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>> -D_FILE_OFFSET_BITS=64 -mlongcalls -mauto-litpools -Os
>> ${CMAKE_C_FLAGS}" CACHE STRING "Buildroot CFLAGS")
>> set(CMAKE_CXX_FLAGS "-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>> -D_FILE_OFFSET_BITS=64 -mlongcalls -mauto-litpools -Os
>> ${CMAKE_CXX_FLAGS}" CACHE STRING "Buildroot CXXFLAGS")
>>
>> But the file
>>   build/opencv3-3.1.0/CMakeCache.txt
>> that governs opencv3 build contains the following lines:
>>
>> //Buildroot CXXFLAGS
>> CMAKE_CXX_FLAGS:STRING=-latomic
>> //Buildroot CFLAGS
>> CMAKE_C_FLAGS:STRING='-D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE
>> -D_FILE_OFFSET_BITS=64 -mlongcalls -mauto-litpools -Os '
>>
>> Below is the output that I see during the failing opencv3 build:
>>
>> --     C++ flags (Release):         -latomic   -fsigned-char -W -Wall
>> -Werror=return-type -Werror=non-virtual-dtor -Werror=address
>> -Werror=sequence-point -Wformat -Werror=format-security
>> -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow
>> -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor
>> -fdiagnostics-show-option -pthread -fomit-frame-pointer
>> -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden
>> -O3 -DNDEBUG  -DNDEBUG
>> --     C++ flags (Debug):           -latomic   -fsigned-char -W -Wall
>> -Werror=return-type -Werror=non-virtual-dtor -Werror=address
>> -Werror=sequence-point -Wformat -Werror=format-security
>> -Wmissing-declarations -Wundef -Winit-self -Wpointer-arith -Wshadow
>> -Wsign-promo -Wno-narrowing -Wno-delete-non-virtual-dtor
>> -fdiagnostics-show-option -pthread -fomit-frame-pointer
>> -ffunction-sections -fvisibility=hidden -fvisibility-inlines-hidden -g
>>  -O0 -DDEBUG -D_DEBUG
>> --     C Compiler:
>> /home/jcmvbkbc/tmp/br/build-20160928-reproduce-opencv/host/usr/bin/xtensa-linux-gcc
>> --     C flags (Release):           -D_LARGEFILE_SOURCE
>> -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -mlongcalls
>> -mauto-litpools -Os    -fsigned-char -W -Wall -Werror=return-type
>> -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point
>> -Wformat -Werror=format-security -Wmissing-declarations
>> -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self
>> -Wpointer-arith -Wshadow -Wno-narrowing -fdiagnostics-show-option
>> -pthread -fomit-frame-pointer -ffunction-sections -fvisibility=hidden
>> -O3 -DNDEBUG  -DNDEBUG
>> --     C flags (Debug):             -D_LARGEFILE_SOURCE
>> -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 -mlongcalls
>> -mauto-litpools -Os    -fsigned-char -W -Wall -Werror=return-type
>> -Werror=non-virtual-dtor -Werror=address -Werror=sequence-point
>> -Wformat -Werror=format-security -Wmissing-declarations
>> -Wmissing-prototypes -Wstrict-prototypes -Wundef -Winit-self
>> -Wpointer-arith -Wshadow -Wno-narrowing -fdiagnostics-show-option
>> -pthread -fomit-frame-pointer -ffunction-sections -fvisibility=hidden
>> -g  -O0 -DDEBUG -D_DEBUG
>>
>> Notice the difference between the C and the C++ flags.
> 
> Indeed, there is a bug in the way we are currently setting/expending
> {C,CXX}FLAGS in the CMake toolchain file.
> I'll post a patch fixing it quickly.
> 
> Regards,
>