[C++-sig] building boost python --threading mystery ?

[Avi Bahra]

Trying to understand --threading option when applied to building boost python
On Linux with gcc it appears to have no effect.

 bjam toolset=gcc --with-python link=shared variant=debug --threading=single
Building the Boost C++ Libraries.
...patience...
...patience...
...found 1489 targets...
...updating 40 targets...
common.mkdir bin.v2
common.mkdir bin.v2/libs
common.mkdir bin.v2/libs/python
common.mkdir bin.v2/libs/python/build
common.mkdir bin.v2/libs/python/build/gcc-4.2.1
common.mkdir bin.v2/libs/python/build/gcc-4.2.1/debug
common.mkdir bin.v2/libs/python/build/gcc-4.2.1/debug/threading-multi
gcc.compile.c++
bin.v2/libs/python/build/gcc-4.2.1/debug/threading-multi/numeric.o


When I specify "--threading=single" it appears to be ignored:
Even putting a rubbish value has no effect ?  --threading=gooblygook

bjam toolset=gcc --with-python link=shared variant=debug --threading=gooblygook
nBuilding the Boost C++ Libraries.nn
...patience...
...patience...
...found 1489 targets...
...updating 19 targets...
gcc.compile.c++
bin.v2/libs/python/build/gcc-4.2.1/debug/threading-multi/object/function.o


However if you have Jamfile that has "using python" like boost python examples
then it gets built as :
bjam
...patience...
...patience...
...patience...
...found 12311 targets...
...updating 42 targets...
common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2
common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs
common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python
common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build
common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1
common.mkdir /var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1/debug
gcc.compile.c++
/var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1/debug/numeric.o
gcc.compile.c++
/var/tmp/ma0/boost/boost_1_43_0/bin.v2/libs/python/build/gcc-4.2.1/debug/list.o

This time there is no mention of threading ?

So it appears that when building boost python at $BOOST_ROOT level it
is fixed as multi threaded
but then gets ignored when building python extensions. The net result
being two builds
of boost python.

Best regards,
Avi