[question] AutoToolsBuildEnvironment: add -stdlib in LDFLAGS if clang?

[SpaceIm]

With AutoToolsBuildEnvironment, I've noticed that -stdlib=libc++ was missing in LDFLAGS while trying to make GDAL recipe works in CCI.
Therefore, GDAL fails to build executables if clang and libc++ on Linux (and shared lib build thanks to some dependencies passing -lc++ (C++ lib with C API) in LIB I think).
As a workaround, I've added CXXFLAGS to link commands creating executables in GDAL.

Shouldn't AutoToolsBuildEnvironment add -stdlib in LDFLAGS env var?

• I've read the CONTRIBUTING guide.

[jgsogo]

I think this is something for the recipe, isn't it? It is something needed only for C++ libraries with a C API or for C libraries linking to C++ ones. IMO it is is something that only the recipe knows as it depends on the library being packaged and/or required.

Probably I'm missing something so I'd more details.

Thanks!

[SpaceIm]

I think this is something for the recipe, isn't it? It is something needed only for C++ libraries with a C API or for C libraries linking to C++ ones

No, I shouldn't have talk about C++ libraries with C API. GDAL has a complex dependency tree but it's unrelated. It's just that, as a lucky side effect of some dependencies propagating -lc++ (thanks to a trick used in the recipe of those dependencies), the issue I describe did not occur while creating the shared lib of GDAL, but afterward when it tries to create GDAL's executables, because -stdlib=libc++ is missing in link command line.

Probably I'm missing something so I'd more details.

What I mean is that using clang with libc++ on Linux seems to require -stdlib=libc++ both in compile AND link command line, therefore AutoToolsBuildEnvironment should probably populate LDFLAGS accordingly.

For example, here are commands for building one executable of gdal:

Compilation:

/bin/bash /tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/libtool --mode=compile --silent --tag=CXX clang++ -std=c++11 -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/port -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/gcore -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/alg -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/ogr -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/ogr/ogrsf_frmts -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/gnm -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/apps -DHAVE_SSE_AT_COMPILE_TIME -m64 -fPIC -stdlib=libc++  -g -DDEBUG -ftrapv -fvisibility=hidden  -Wall -Wextra -Winit-self -Wunused-parameter -Wformat -Werror=format-security -Wno-format-nonliteral -Wshorten-64-to-32 -Wshadow -Werror=vla -Wdate-time -Wnull-dereference -Wextra-semi -Wcomma -Wfloat-conversion -Wdocumentation -Wno-documentation-deprecated-sync -Wunused-private-field -Wmissing-declarations -Wnon-virtual-dtor -Woverloaded-virtual -fno-operator-names -Wzero-as-null-pointer-constant -Wimplicit-fallthrough  -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/frmts/vrt -DGNM_ENABLED -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/json-c/0.13.1/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libgeotiff/1.6.0/_/_/package/a9fbdb19bebdff8d60cc4f20198ff2e86ea26a06/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/flatbuffers/1.12.0/_/_/package/ab1732eaa9b018f8ce55e42c1863eee4f20db10b/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libiconv/1.16/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libpng/1.6.37/_/_/package/a5db9977b995c3a52f6068c4befeb555e2aa78ee/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/giflib/5.1.4/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/geos/3.8.1/_/_/package/819c37cee2f8127f8ac8b5386c4ba4a3c58e0afb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/proj/7.0.0/_/_/package/9e8e2da8da6517b3d18441049c73f8deeec5224e/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libtiff/4.1.0/_/_/package/4cfb872a7d959dfb53da0abead498a7ffe3cbe72/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/sqlite3/3.31.1/_/_/package/8726bdb7fed1c9d10784d2490c79f6b14c4fe44d/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libcurl/7.69.1/_/_/package/32b2c6d4da512dd3d22600a1021c80fca6ac4095/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/zlib/1.2.11/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/xz_utils/5.2.4/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libjpeg/9d/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/jbig/20160605/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/zstd/1.4.3/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libwebp/1.0.3/_/_/package/6a842bb5bec37e0c6199fd57aedd95fdcc7cbc98/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/openssl/1.1.1g/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -DLIBJPEG_STATIC -DLZMA_API_STATIC -DCURL_STATICLIB=1 -DGEOS_INLINE -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/port -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/giflib/5.1.4/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/giflib/5.1.4/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libjpeg/9d/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libjpeg/9d/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libgeotiff/1.6.0/_/_/package/a9fbdb19bebdff8d60cc4f20198ff2e86ea26a06/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libtiff/4.1.0/_/_/package/4cfb872a7d959dfb53da0abead498a7ffe3cbe72/include -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libpng/1.6.37/_/_/package/a5db9977b995c3a52f6068c4befeb555e2aa78ee -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libpng/1.6.37/_/_/package/a5db9977b995c3a52f6068c4befeb555e2aa78ee/include  -DGDAL_COMPILATION -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/json-c/0.13.1/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/include/json-c  -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/ogr/ogrsf_frmts/geojson -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/ogr/ogrsf_frmts/generic -g -I/tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/gnm -c -o gdaladdo.lo gdaladdo.cpp

Link:

/bin/bash /tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/libtool --mode=link --silent clang++ -std=c++11 -m64 -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/json-c/0.13.1/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libgeotiff/1.6.0/_/_/package/a9fbdb19bebdff8d60cc4f20198ff2e86ea26a06/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/flatbuffers/1.12.0/_/_/package/ab1732eaa9b018f8ce55e42c1863eee4f20db10b/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libiconv/1.16/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libpng/1.6.37/_/_/package/a5db9977b995c3a52f6068c4befeb555e2aa78ee/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/giflib/5.1.4/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/geos/3.8.1/_/_/package/819c37cee2f8127f8ac8b5386c4ba4a3c58e0afb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/proj/7.0.0/_/_/package/9e8e2da8da6517b3d18441049c73f8deeec5224e/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libtiff/4.1.0/_/_/package/4cfb872a7d959dfb53da0abead498a7ffe3cbe72/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/sqlite3/3.31.1/_/_/package/8726bdb7fed1c9d10784d2490c79f6b14c4fe44d/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libcurl/7.69.1/_/_/package/32b2c6d4da512dd3d22600a1021c80fca6ac4095/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/zlib/1.2.11/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/xz_utils/5.2.4/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libjpeg/9d/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/jbig/20160605/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/zstd/1.4.3/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/libwebp/1.0.3/_/_/package/6a842bb5bec37e0c6199fd57aedd95fdcc7cbc98/lib -L/tmp/c3ipr/pr_1722_5_0_48/.conan/data/openssl/1.1.1g/_/_/package/689541ef75e69f6ec6dadbae4187260d6a3f4cfb/lib gdaladdo.lo  /tmp/c3ipr/pr_1722_5_0_48/.conan/data/gdal/3.1.0/_/_/build/24258629af78ec0a2e509c7d4fa7fdf23ae5f854/source_subfolder/libgdal.la -o gdaladdo

Error at link time:

/usr/bin/ld: .libs/gdaladdo.o: undefined reference to symbol '_ZNSt3__112basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEE6__initEPKcm'
//usr/lib/x86_64-linux-gnu/libc++.so.1: error adding symbols: DSO missing from command line
clang: error: linker command failed with exit code 1 (use -v to see invocation)

Each command is a little bit long :p but you can see that -stdlib=libc++ is used for compilation but not for link. If -stdlib=libc++ is also added for link, it works.