And make `core:terminal` use it so that `core:log` can be imported with `-default-to-nil-allocator`,
in which the actual allocator is set up in `main()`.
Windows was tricky because of the utf-8 <> utf-16 conversion, so we use some temporary stack buffers for that purpose,
limiting the non-allocating version there to 512 utf-16 characters each for the key and environment value.
In general the value is (obviously) limited to the size of the supplied buffer, and a `.Buffer_Full` error is returned
if that buffer is insufficient. If the key is not found, the procedure returns `.Env_Var_Not_Found`.
TODO:
- Factor out buffer-backed utf8 + utf16 conversion to `core:sys/util` to more easily apply this pattern.
- Add similar `lookup_env` and `get_env` procedures to `core:os/os2`.
Fixes#5336
os.args is never freed, while this is an insignificant leak, it is a bit
annoying as it makes valgrind complain:
==234270== Memcheck, a memory error detector
==234270== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==234270== Using Valgrind-3.24.0 and LibVEX; rerun with -h for copyright info
==234270== Command: ./wc /tmp/mulumulu
==234270==
1 8 58 /tmp/mulumulu
==234270==
==234270== HEAP SUMMARY:
==234270== in use at exit: 47 bytes in 1 blocks
==234270== total heap usage: 5 allocs, 4 frees, 4,195,875 bytes allocated
==234270==
==234270== 47 bytes in 1 blocks are possibly lost in loss record 1 of 1
==234270== at 0x484BC13: calloc (vg_replace_malloc.c:1675)
==234270== by 0x402E49: runtime._heap_alloc-769 (in /d/learn-odin/wc/wc)
==234270== by 0x40A8D7: runtime.heap_alloc (in /d/learn-odin/wc/wc)
==234270== by 0x436E9D: runtime.heap_allocator_proc.aligned_alloc-0 (in /d/learn-odin/wc/wc)
==234270== by 0x4022DC: runtime.heap_allocator_proc (in /d/learn-odin/wc/wc)
==234270== by 0x4165E0: runtime.make_aligned-22560 (in /d/learn-odin/wc/wc)
==234270== by 0x41F6D0: runtime.make_slice-22340 (in /d/learn-odin/wc/wc)
==234270== by 0x40156B: os._alloc_command_line_arguments-4679 (in /d/learn-odin/wc/wc)
==234270== by 0x4011AF: __$startup_runtime (in /d/learn-odin/wc/wc)
==234270== by 0x406F17: main (in /d/learn-odin/wc/wc)
==234270==
==234270== LEAK SUMMARY:
==234270== definitely lost: 0 bytes in 0 blocks
==234270== indirectly lost: 0 bytes in 0 blocks
==234270== possibly lost: 47 bytes in 1 blocks
==234270== still reachable: 0 bytes in 0 blocks
==234270== suppressed: 0 bytes in 0 blocks
==234270==
==234270== For lists of detected and suppressed errors, rerun with: -s
==234270== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
With the fix the leak is gone, tested on linux only.
While here, also make _alloc_command_line_arguments() private.
