Previously, the build system used uname(1) output when it wanted to
check the operating system it was being built for, which meant that it
didn't take into-account cross-compilation when the build and host
operating systems were different.
To fix this, instead of consulting uname output, we consult the host
triple, specifically the third "kernel" part.
For "kernel"s with stable ABIs, like Linux or Cygwin, we can use a
simple ifeq to test whether we're compiling for that system, but for
other platforms, like Darwin, FreeBSD, or Solaris, we have to use a
more complicated check to take into account the version numbers at the
end of the "kernel"s. I couldn't find a way to just strip these
version numbers in GNU Make without shelling out, which would be even
more ugly IMO. Because these checks differ between kernels, and the
patsubst ones are quite fiddly, I've added variables for each host OS
we might want to check to make them easier to reuse.
This combines the *.o into a big .o producing one translation unit.
This preserve our unused static initializers, as specified in the C++
standard:
If no variable or function is odr-used from a given translation
unit, the non-local variables defined in that translation unit may
never be initialized (this models the behavior of an on-demand
dynamic library).
Note that this is very similar to how the --whole-archive flag works.
One advantage of this is that users of the final .a library don’t have
to worry about specifying --whole-archive, or that we have unused
static initializers at all!
autotools-based systems usually allow user to
append own LDFLAGS like
LDFLAGS="-Wl,-O1 -Wl,--as-needed -Wl,--hash-style=gnu"
at ./configure stage
This change plumbs LDFLAGS through similar to existing CXXFLAGS variable.
Signed-off-by: Sergei Trofimovich <siarheit@google.com>
