The goal is to support libeditline AND libreadline and let the user
decide at compile time which one to use.
Add a compile time option to use libreadline instead of
libeditline. If compiled against libreadline completion functionality
is lost because of a incompatibility between libeditlines and
libreadlines completion function. Completion with libreadline is
possible and can be added later.
To use libreadline instead of libeditline the environment
variables 'EDITLINE_LIBS' and 'EDITLINE_CFLAGS' have to been set
during the ./configure step.
Example:
EDITLINE_LIBS="/usr/lib/x86_64-linux-gnu/libhistory.so /usr/lib/x86_64-linux-gnu/libreadline.so"
EDITLINE_CFLAGS="-DREADLINE"
The reason for this change is that for example on Debian already three
different editline libraries exist but none of those is compatible the
flavor used by nix. My hope is that with this change it would be
easier to port nix to systems that have already libreadline available.
EvalState contains a few counters (e.g. nrValues) that increase
quickly enough that they end up being interpreted as pointers by the
garbage collector. Moving it to the heap makes them invisible to the
garbage collector.
This reduces the max RSS doing 100 evaluations of
nixos.tests.firefox.x86_64-linux.drvPath from 455 MiB to 292 MiB.
Note: ideally, allocations would be much further up in the 64-bit
address space to reduce the odds of an integer being misinterpreted as
a pointer. Maybe we can use some linker magic to move the .bss segment
to a higher address.
