boost build issue with -Wl,--as-needed or binutils-gold

[Andreas Metzler]

Hello,

programs including the boost_filesystem headers also should be linked against *both* boost_filesystem headers and boost system, since boost_system functions are invoked directly via inline functions in the boost_filesystem headers. The autoconf setup of enblend-enfuse does not do this.

enblend 4.0 will therefore fail to build from source if binutils-gold is used or LDFLAGS="-Wl,--as-needed" is set:
----------------------------------------------------------------
i686-linux-gnu-g++ -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -I../../include -DVIGRA_STATIC_LIB -pthread -I/usr/include/OpenEXR -Wall -g -O2 -fopenmp -Wl,-Bsymbolic-functions -o enblend enblend-enblend.o enblend-gpu.o enblend-error_message.o enblend-filenameparse.o enblend-filespec.o enblend-self_test.o enblend-tiff_message.o vigra_impex/libvigra_impex.a -lGLEW -lGLU -lGL -lm -lglut -lGLU -lGL -lm -lboost_filesystem -pthread -lIlmImf -lz -lImath -lHalf -lIex -lIlmThread -lxmi -llcms -ltiff -lpng -ljpeg -lz
enblend-filenameparse.o: In function `__static_initialization_and_destruction_0':
/usr/include/boost/system/error_code.hpp:208: undefined reference to `boost::system::get_system_category()'
/usr/include/boost/system/error_code.hpp:209: undefined reference to `boost::system::get_generic_category()'
/usr/include/boost/system/error_code.hpp:214: undefined reference to `boost::system::get_generic_category()'
/usr/include/boost/system/error_code.hpp:215: undefined reference to `boost::system::get_generic_category()'
/usr/include/boost/system/error_code.hpp:216: undefined reference to `boost::system::get_system_category()'
collect2: ld returned 1 exit status
make[5]: *** [enblend] Error 1
-----------------------------------------------

hg head behaves slightly differently, the autoconf test fails and the build falls back to Boost's generic filename parsing. The cmake setup already checks for both libraries afaict.

FWIW Ubuntu linux has recently enabled LDFLAGS="-Wl,--as-needed" by default.

Works-for-me patch attached.

[Andreas Metzler (k-launchpad-downhill-at-eu-org)]

The file asneeded.diff was added: suggested path for hg head