Appendix: the VM footprint number doesn't really give us a breakdown since it includes executable and shared libs mappings. I ran the second compile again with the memory-optimized build, and this time captured a pmap.

Here you can also see the full command, confirming the compile job:

  $ pmap 24087
  24087:   ./txr --in-package=sys --compile=stdlib/compiler.tl:stdlib/compiler.tlo.tmp
  08048000   1660K r-x-- txr
  081e7000      4K r---- txr
  081e8000     12K rw--- txr
  081eb000    124K rw---   [ anon ]
  08c03000   6188K rw---   [ anon ]
  b7c5e000      8K rw---   [ anon ]
  b7c60000   1876K r-x-- libc-2.27.so
  b7e35000      4K ----- libc-2.27.so
  b7e36000      8K r---- libc-2.27.so
  b7e38000      4K rw--- libc-2.27.so
  b7e39000     12K rw---   [ anon ]
  b7e3c000    116K r-x-- libz.so.1.2.11
  b7e59000      4K r---- libz.so.1.2.11
  b7e5a000      4K rw--- libz.so.1.2.11
  b7e5b000     28K r-x-- libffi.so.6.0.4
  b7e62000      4K r---- libffi.so.6.0.4
  b7e63000      4K rw--- libffi.so.6.0.4
  b7e64000     12K r-x-- libdl-2.27.so
  b7e67000      4K r---- libdl-2.27.so
  b7e68000      4K rw--- libdl-2.27.so
  b7e69000     36K r-x-- libcrypt-2.27.so
  b7e72000      4K r---- libcrypt-2.27.so
  b7e73000      4K rw--- libcrypt-2.27.so
  b7e74000    156K rw---   [ anon ]
  b7e9b000   1024K r-x-- libm-2.27.so
  b7f9b000      4K r---- libm-2.27.so
  b7f9c000      4K rw--- libm-2.27.so
  b7fba000      8K rw---   [ anon ]
  b7fbc000     12K r----   [ anon ]
  b7fbf000      8K r-x--   [ anon ]
  b7fc1000    152K r-x-- ld-2.27.so
  b7fe7000      4K r---- ld-2.27.so
  b7fe8000      4K rw--- ld-2.27.so
  bf8d9000    200K rw---   [ stack ]
   total    11700K

You can see the 11700K fairly closely matches the earlier VIRT figure of 11964.

Anyway, look at the [ anon ] heap area: it's like 6-something megs. That's it. That's where all the dynamic Lisp stuff is. All the predefined symbols and function bindings and whatnot, and all the objects allocated during the compile job.

libz is new; I integrated libz into TXR in just the most recent release. It happens to be number 277, so I code named it (L)Z77.