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43 commits

Author SHA1 Message Date
jade 789b19a0cf util: fix brotli decompression of empty input
This caused an infinite loop before since it would just keep asking the
underlying source for more data.

In practice this happened because an HTTP server served a
response to a HEAD request (for which curl will not retrieve any body or
call our write callback function) with Content-Encoding: br, leading to
decompressing nothing at all and going into an infinite loop.

This adds a test to make sure none of our compression methods do that
again, as well as just patching the HTTP client to never feed empty data
into a compression algorithm (since they absolutely have the right to
throw CompressionError on unexpectedly-short streams!).

Reported on Matrix: https://matrix.to/#/!lymvtcwDJ7ZA9Npq:lix.systems/$8BWQR_zKxCQDJ40C5NnDo4bQPId3pZ_aoDj2ANP7Itc?via=lix.systems&via=matrix.org&via=tchncs.de

Change-Id: I027566e280f0f569fdb8df40e5ecbf46c211dad1
2024-09-18 15:37:29 -07:00
jade 4046e019ca tests/compression: rewrite
This test suite was in desperate need of using the parameterization
available with gtest, and was a bunch of useless duplicated code. At
least now it's not duplicated code, though it still probably should be
more full of property tests.

Change-Id: Ia8ccee7ef4f02b2fa40417b79aa8c8f0626ea479
2024-09-17 19:07:48 -07:00
Rebecca Turner 75c0de3e3c
Test including relative paths in configuration
Change-Id: If6c69a5e16d1ccd223fba392890f08f0032fb754
2024-09-01 15:52:48 -07:00
Rebecca Turner 02eb07cfd5 Merge changes I5566a985,I88cf53d3 into main
* changes:
  Support relative and `~/` paths in config settings
  Thread `ApplyConfigOptions` through config parsing
2024-09-01 22:06:36 +00:00
jade 04f8a14833
tree-wide: shuffle headers around for about 30s compile time
This didn't really feel so worth it afterwards, but I did untangle a
bunch of stuff that should not have been tangled.

The general gist of this change is that variant bullshit was causing a
bunch of compile time, and it seems like the only way to deal with
variant induced compile time is to keep variant types out of headers.
Explicit template instantiation seems to do nothing for them.

I also seem to have gotten some back-end time improvement from
explicitly instantiating regex, but I don't know why. There is no
corresponding front-end time improvement from it: regex is still at the
top of the sinners list.

**** Templates that took longest to instantiate:
 15231 ms: std::basic_regex<char>::_M_compile (28 times, avg 543 ms)
 15066 ms: std::__detail::_Compiler<std::regex_traits<char>>::_Compiler (28 times, avg 538 ms)
 12571 ms: std::__detail::_Compiler<std::regex_traits<char>>::_M_disjunction (28 times, avg 448 ms)
 12454 ms: std::__detail::_Compiler<std::regex_traits<char>>::_M_alternative (28 times, avg 444 ms)
 12225 ms: std::__detail::_Compiler<std::regex_traits<char>>::_M_term (28 times, avg 436 ms)
 11363 ms: nlohmann::basic_json<>::parse<const char *> (21 times, avg 541 ms)
 10628 ms: nlohmann::basic_json<>::basic_json (109 times, avg 97 ms)
 10134 ms: std::__detail::_Compiler<std::regex_traits<char>>::_M_atom (28 times, avg 361 ms)

Back-end time before messing with the regex:
**** Function sets that took longest to compile / optimize:
  8076 ms: void boost::io::detail::put<$>(boost::io::detail::put_holder<$> cons... (177 times, avg 45 ms)
  4382 ms: std::_Rb_tree<$>::_M_erase(std::_Rb_tree_node<$>*) (1247 times, avg 3 ms)
  3137 ms: boost::stacktrace::detail::to_string_impl_base<boost::stacktrace::de... (137 times, avg 22 ms)
  2896 ms: void boost::io::detail::mk_str<$>(std::__cxx11::basic_string<$>&, ch... (177 times, avg 16 ms)
  2304 ms: std::_Rb_tree<$>::_M_get_insert_hint_unique_pos(std::_Rb_tree_const_... (210 times, avg 10 ms)
  2116 ms: bool std::__detail::_Compiler<$>::_M_expression_term<$>(std::__detai... (112 times, avg 18 ms)
  2051 ms: std::_Rb_tree_iterator<$> std::_Rb_tree<$>::_M_emplace_hint_unique<$... (244 times, avg 8 ms)
  2037 ms: toml::result<$> toml::detail::sequence<$>::invoke<$>(toml::detail::l... (93 times, avg 21 ms)
  1928 ms: std::__detail::_Compiler<$>::_M_quantifier() (28 times, avg 68 ms)
  1859 ms: nlohmann::json_abi_v3_11_3::detail::serializer<$>::dump(nlohmann::js... (41 times, avg 45 ms)
  1824 ms: std::_Function_handler<$>::_M_manager(std::_Any_data&, std::_Any_dat... (973 times, avg 1 ms)
  1810 ms: std::__detail::_BracketMatcher<$>::_BracketMatcher(std::__detail::_B... (112 times, avg 16 ms)
  1793 ms: nix::fetchers::GitInputScheme::fetch(nix::ref<$>, nix::fetchers::Inp... (1 times, avg 1793 ms)
  1759 ms: std::_Rb_tree<$>::_M_get_insert_unique_pos(std::__cxx11::basic_strin... (281 times, avg 6 ms)
  1722 ms: bool nlohmann::json_abi_v3_11_3::detail::parser<$>::sax_parse_intern... (19 times, avg 90 ms)
  1677 ms: boost::io::basic_altstringbuf<$>::overflow(int) (194 times, avg 8 ms)
  1674 ms: std::__cxx11::basic_string<$>::_M_mutate(unsigned long, unsigned lon... (249 times, avg 6 ms)
  1660 ms: std::_Rb_tree_node<$>* std::_Rb_tree<$>::_M_copy<$>(std::_Rb_tree_no... (304 times, avg 5 ms)
  1599 ms: bool nlohmann::json_abi_v3_11_3::detail::parser<$>::sax_parse_intern... (19 times, avg 84 ms)
  1568 ms: void std::__detail::_Compiler<$>::_M_insert_bracket_matcher<$>(bool) (112 times, avg 14 ms)
  1541 ms: std::__shared_ptr<$>::~__shared_ptr() (531 times, avg 2 ms)
  1539 ms: nlohmann::json_abi_v3_11_3::detail::serializer<$>::dump_escaped(std:... (41 times, avg 37 ms)
  1471 ms: void std::__detail::_Compiler<$>::_M_insert_character_class_matcher<... (112 times, avg 13 ms)

After messing with the regex (notice std::__detail::_Compiler vanishes
here, but I don't know why):

**** Function sets that took longest to compile / optimize:
  8054 ms: void boost::io::detail::put<$>(boost::io::detail::put_holder<$> cons... (177 times, avg 45 ms)
  4313 ms: std::_Rb_tree<$>::_M_erase(std::_Rb_tree_node<$>*) (1217 times, avg 3 ms)
  3259 ms: boost::stacktrace::detail::to_string_impl_base<boost::stacktrace::de... (137 times, avg 23 ms)
  3045 ms: void boost::io::detail::mk_str<$>(std::__cxx11::basic_string<$>&, ch... (177 times, avg 17 ms)
  2314 ms: std::_Rb_tree<$>::_M_get_insert_hint_unique_pos(std::_Rb_tree_const_... (207 times, avg 11 ms)
  1923 ms: std::_Rb_tree_iterator<$> std::_Rb_tree<$>::_M_emplace_hint_unique<$... (216 times, avg 8 ms)
  1817 ms: bool nlohmann::json_abi_v3_11_3::detail::parser<$>::sax_parse_intern... (18 times, avg 100 ms)
  1816 ms: toml::result<$> toml::detail::sequence<$>::invoke<$>(toml::detail::l... (93 times, avg 19 ms)
  1788 ms: nlohmann::json_abi_v3_11_3::detail::serializer<$>::dump(nlohmann::js... (40 times, avg 44 ms)
  1749 ms: std::_Rb_tree<$>::_M_get_insert_unique_pos(std::__cxx11::basic_strin... (278 times, avg 6 ms)
  1724 ms: std::__cxx11::basic_string<$>::_M_mutate(unsigned long, unsigned lon... (248 times, avg 6 ms)
  1697 ms: boost::io::basic_altstringbuf<$>::overflow(int) (194 times, avg 8 ms)
  1684 ms: nix::fetchers::GitInputScheme::fetch(nix::ref<$>, nix::fetchers::Inp... (1 times, avg 1684 ms)
  1680 ms: std::_Rb_tree_node<$>* std::_Rb_tree<$>::_M_copy<$>(std::_Rb_tree_no... (303 times, avg 5 ms)
  1589 ms: bool nlohmann::json_abi_v3_11_3::detail::parser<$>::sax_parse_intern... (18 times, avg 88 ms)
  1483 ms: non-virtual thunk to boost::wrapexcept<$>::~wrapexcept() (181 times, avg 8 ms)
  1447 ms: nlohmann::json_abi_v3_11_3::detail::serializer<$>::dump_escaped(std:... (40 times, avg 36 ms)
  1441 ms: std::__shared_ptr<$>::~__shared_ptr() (496 times, avg 2 ms)
  1420 ms: boost::stacktrace::basic_stacktrace<$>::init(unsigned long, unsigned... (137 times, avg 10 ms)
  1396 ms: boost::basic_format<$>::~basic_format() (194 times, avg 7 ms)
  1290 ms: std::__cxx11::basic_string<$>::_M_replace_cold(char*, unsigned long,... (231 times, avg 5 ms)
  1258 ms: std::vector<$>::~vector() (354 times, avg 3 ms)
  1222 ms: std::__cxx11::basic_string<$>::_M_replace(unsigned long, unsigned lo... (231 times, avg 5 ms)
  1194 ms: std::_Rb_tree<$>::_M_get_insert_hint_unique_pos(std::_Rb_tree_const_... (49 times, avg 24 ms)
  1186 ms: bool tao::pegtl::internal::sor<$>::match<$>(std::integer_sequence<$>... (1 times, avg 1186 ms)
  1149 ms: std::__detail::_Executor<$>::_M_dfs(std::__detail::_Executor<$>::_Ma... (70 times, avg 16 ms)
  1123 ms: toml::detail::sequence<$>::invoke(toml::detail::location&) (69 times, avg 16 ms)
  1110 ms: nlohmann::json_abi_v3_11_3::basic_json<$>::json_value::destroy(nlohm... (55 times, avg 20 ms)
  1079 ms: std::_Function_handler<$>::_M_manager(std::_Any_data&, std::_Any_dat... (541 times, avg 1 ms)
  1033 ms: nlohmann::json_abi_v3_11_3::detail::lexer<$>::scan_number() (20 times, avg 51 ms)

Change-Id: I10af282bcd4fc39c2d3caae3453e599e4639c70b
2024-08-28 09:55:05 -07:00
jade 0cc285f87b
treewide: fix a bunch of lints
Fixes:
- Identifiers starting with _ are prohibited
- Some driveby header dependency cleaning which wound up with doing some
  extra fixups.
- Fucking C style casts, man. C++ made these 1000% worse by letting you
  also do memory corruption with them with references.
  - Remove casts to Expr * where ExprBlackHole is an incomplete type by
    introducing an explicitly-cast eBlackHoleAddr as Expr *.
  - An incredibly illegal cast of the text bytes of the StorePath hash
    into a size_t directly. You can't DO THAT.

    Replaced with actually parsing the hash so we get 100% of the bits
    being entropy, then memcpying the start of the hash. If this shows
    up in a profile we should just make the hash parser faster with a
    lookup table or something sensible like that.
  - This horrendous bit of UB which I thankfully slapped a deprecation
    warning on, built, and it didn't trigger anywhere so it was dead
    code and I just deleted it. But holy crap you *cannot* do that.

    inline void mkString(const Symbol & s)
    {
        mkString(((const std::string &) s).c_str());
    }
- Some wrong lints. Lots of wrong macro lints, one wrong
  suspicious-sizeof lint triggered by the template being instantiated
  with only pointers, but the calculation being correct for both
  pointers and not-pointers.
- Exceptions in destructors strike again. I tried to catch the
  exceptions that might actually happen rather than all the exceptions
  imaginable. We can let the runtime hard-kill it on other exceptions
  imo.

Change-Id: I71761620846cba64d66ee7ca231b20c061e69710
2024-08-26 16:13:03 -07:00
Rebecca Turner 690f07272e
Support relative and ~/ paths in config settings
Change-Id: I5566a9858ba255f4ac5051d1368c7dfb24460f0a
2024-08-25 15:54:22 -07:00
Rebecca Turner 5fc6fcb310
Thread ApplyConfigOptions through config parsing
This makes no changes to logic but makes the `ApplyConfigOptions` value
available to consumers.

Change-Id: I88cf53d38faac8472c556aee55c13d0acbd1e5db
2024-08-25 15:54:22 -07:00
alois31 e3c289dbe9
libutil/config: unify path setting types
There have been multiple setting types for paths that are supposed to be
canonicalised, depending on whether zero or one, one, or any number of paths is
to be specified. Naturally, they behaved in slightly different ways in the
code. Simplify things by unifying them and removing special behaviour (mainly
the "multiple paths type can coerce to boolean" thing).

Change-Id: I7c1ce95e9c8e1829a866fb37d679e167811e9705
2024-08-21 17:57:23 +02:00
jade e34833c025 tree-wide: fix a pile of lints
This:
- Converts a bunch of C style casts into C++ casts.
- Removes some very silly pointer subtraction code (which is no more or
  less busted on i686 than it began)
- Fixes some "technically UB" that never had to be UB in the first
  place.
- Makes finally follow the noexcept status of the inner function. Maybe
  in the future we should ban the function from not being noexcept, but
  that is not today.
- Makes various locally-used exceptions inherit from std::exception.

Change-Id: I22e66972602604989b5e494fd940b93e0e6e9297
2024-08-08 14:53:17 -07:00
jade 370ac940dd refactor: make HashType and Base enum classes for type safety
Change-Id: I9fbd55a9d50464a56fe11cb42a06a206914150d8
2024-08-08 14:53:17 -07:00
jade f9641b9efd libutil: add checked arithmetic tools
This is in preparation for adding checked arithmetic to the evaluator.

Change-Id: I6e115ce8f5411feda1706624977a4dcd5efd4d13
2024-07-13 00:56:37 +02:00
eldritch horrors df8851f286 libutil: rewrite RewritingSink as source
the rewriting sink was just broken. when given a rewrite set that
contained a key that is also a proper infix of another key it was
possible to produce an incorrectly rewritten result if the writer
used the wrong block size. fixing this duplicates rewriteStrings,
to avoid this we'll rewrite rewriteStrings to use RewritingSource
in a new mode that'll allow rewrites we had previously forbidden.

Change-Id: I57fa0a9a994e654e11d07172b8e31d15f0b7e8c0
2024-07-11 11:39:18 +00:00
eldritch horrors b51ea465de libutil: allow construction of sources from generators
Change-Id: I78ff8d0720f06bce731e26d5e1c53b1382bbd589
2024-07-05 22:28:16 +00:00
eldritch horrors 5eec6418de libutil: begin porting serialization to generators
generators are a better basis for serializers than streaming into sinks
as we do currently for many reasons, such as being usable as sources if
one wishes to (without requiring an intermediate sink to serialize full
data sets into memory, or boost coroutines to turn sinks into sources),
composing more naturally (as one can just yield a sub-generator instead
of being forced to wrap entire substreams into clunky functions or even
more clunky custom types to implement operator<< on), allowing wrappers
to transform data with clear ownership semantics (removing the need for
explicit memory allocations and Source wrappers), and many other things

Change-Id: I361d89ff556354f6930d9204f55117565f2f7f20
2024-07-03 11:46:53 +00:00
eldritch horrors 73ddc4540f libutil: generator type with on-yield value mapping
this will be the basis of non-boost coroutines in lix. anything that is
a boost coroutine *should* be representable with a Generator coroutine,
and many things that are not currently boost coroutines but behave much
like one (such as, notably, serializers) should be as well. this allows
us to greatly simplify many things that look like iteration but aren't.

Change-Id: I2cebcefa0148b631fb30df4c8cfa92167a407e34
2024-07-03 11:46:53 +00:00
eldritch horrors a9949f4760 libutil: add some serialize.hh serializer tests
Change-Id: I0116265a18bc44bba16c07bf419af70d5195f07d
2024-06-23 11:52:49 +00:00
Ilya K 7d52d74bbe BrotliDecompressionSource: don't bail out too early
If we've consumed the entire input, that doesn't actually mean we're
done decompressing - there might be more output left. This worked (?)
in most cases because the input and output sizes are pretty comparable,
but sometimes they're not and then things get very funny.

Change-Id: I73435a654a911b8ce25119f713b80706c5783c1b
2024-06-20 09:21:13 +03:00
eldritch horrors 67f778670c libutil: add makeDecompressionSource
Change-Id: Iac7f24d79e24417436b9b5cbefd6af051aeea0a6
2024-06-19 10:50:12 +00:00
Tom Hubrecht a39ba22ff7 util.hh: Delete remaining file and clean up headers
Change-Id: Ic1f68e6af658e94ef7922841dd3ad4c69551ef56
2024-05-29 12:38:51 +02:00
Tom Hubrecht b910551120 util.{hh,cc}: Split out strings.{hh,cc}
Change-Id: I4f642d1046d56b5db26f1b0296ee16a0e02d444a
2024-05-29 11:01:34 +02:00
Tom Hubrecht 9a52e4688c util.{hh,cc}: Split out processes.{hh,cc}
Change-Id: I39280dc40ca3f7f9007bc6c898ffcf760e2238b7
2024-05-29 11:01:34 +02:00
Tom Hubrecht 6b5078c815 util.{hh,cc}: Split out file-system.{hh,cc}
Change-Id: Ifa89a529e7e34e7291eca87d802d2f569cf2493e
2024-05-29 09:54:47 +02:00
Tom Hubrecht 81bdf8d2d6 util.{hh,cc}: Split out terminal.{hh,cc}
Change-Id: I9de2296b4012d50f540124001d54d6ca3be4c6da
2024-05-29 09:54:47 +02:00
Qyriad b9be46fb31 remove the autoconf+Make buildsystem
We're not using it anymore. Any leftover bugs in the Meson buildsystem
are now just bugs.

Closes #249.

Change-Id: I0465a0c37ae819f94d40e7829f5bff046aa63d73
2024-05-07 17:04:30 -06:00
eldritch horrors 964ac8b0e8 libutil: de-callback-ify computeClosure
only two users of this function exist. only one used it in a way that
even bears resemblance to asynchronicity, and even that one didn't do
it right. fully async and parallel computation would have only worked
if any getEdgesAsync never calls the continuation it receives itself,
only from more derived callbacks running on other threads. calling it
directly would cause the decoupling promise to be awaited immediately
*on the original thread*, completely negating all nice async effects.

Change-Id: I0aa640950cf327533a32dee410105efdabb448df
2024-05-07 14:35:20 +00:00
eldritch horrors d55b158e24 libutil: make rewriteStrings sound
this is used in CA rewriting, replacement of placeholders in
derivations, generating scripts for devShells, and some more
places. in all of these transitive replacements are unsound,
and overlapping replacements would be as well. there even is
a test that transitive replacements do not happen (in the CA
RewriteSink suite), but none for overlapping replacements. a
minimally surprising binary rewriter surely would not do any
of these replacements, the only reason we have not seen this
break yet is probably that rewriteStrings is only called for
store paths and things that look like store paths (and those
should never overlap nor admit such transitive replacements)

Change-Id: I6fc29f939d5061d9f56c752624a823ece8437c07
2024-05-03 00:50:31 +00:00
Eelco Dolstra ce70f02aff getNameFromURL(): Support uppercase characters in attribute names
In particular, this makes it handle 'legacyPackages' correctly.

(cherry picked from commit 936a3642264ac159f3f9093710be3465b70e0e89)

Upstream-PR: https://github.com/NixOS/nix/pull/9657
Change-Id: Icc4efe02f7f8e90a2970589f72fd3d3cd4418d95
2024-05-02 12:02:28 -06:00
Qyriad 1425aa0b7c implement parsing human-readable names from URLs
Based off of commit 257b768436a0e8ab7887f9b790c5b92a7fe51ef5

Upstream-PR: https://github.com/NixOS/nix/pull/8678
Co-authored-by: Felix Uhl <felix.uhl@outlook.com>
Change-Id: Idcb7f6191ca3310ef9dc854197f7798260c3f71d
2024-04-30 18:11:14 -06:00
Qyriad 4e68deef80 abort with a descriptive message on bad HintFmt usage
Change-Id: Ic2f05572042343a8160fd971394372f5f2706fc4
2024-04-15 23:09:16 +00:00
Rebecca Turner 6f863e8ccd Add PathsSetting
Change-Id: I1165f6ef033a5f757ca3716d3f8008ba36b01fd0
2024-04-07 18:22:15 -07:00
eldritch horrors 38dc6f5b69 Revert "libutil: drop Pool resources on exceptional free"
This reverts commit de2884b82b376d10de5c400d8e73bc7d98f195d2.

Change-Id: I1fa301149d7c2ed3d266a40c15b2d010e12e44e6
2024-04-05 20:13:02 +00:00
Rebecca Turner ea10fe7ab0 Add EscapeStringOptions and escapeString tests
Change-Id: I86ead2f969c9e03c9edfa51bbc92ee06393fd7d6
2024-04-03 16:25:54 +00:00
eldritch horrors 862f20a4ba libutil: remove Pool::flushBad
this was never actually used, and bad design in the first place—why
should a bad resource be put back into the idle pool? just drop it.

Change-Id: Idab8774bee19dadae0209d404c4fb86dd4aeba1e
2024-03-31 00:07:09 +00:00
eldritch horrors 620de98d0c libutil: drop Pool resources on exceptional free
if a scope owning a resource does not gracefully drop that resource
while handling exceptions from deeper down the call stack we should
assume the resource is invalid state and drop it. currently it *is*
true that such cases do not cause resources to be freed, but thanks
to validator misuses this has so far not caused any larger problem.

Change-Id: Ie4f91bcd60a64d05c5ff9d22cc97954816d13b97
2024-03-30 23:40:45 +00:00
Rebecca Turner 2a98ba8b97 Add pre-commit checks
The big ones here are `trim-trailing-whitespace` and `end-of-file-fixer`
(which makes sure that every file ends with exactly one newline
character).

Change-Id: Idca73b640883188f068f9903e013cf0d82aa1123
2024-03-29 22:57:40 -07:00
Rebecca Turner 236bc046ba Merge "Remove HintFmt::operator%" into main 2024-03-29 01:13:45 +00:00
Rebecca Turner aee3d639b5 Move shell_words into its own file
Change-Id: I34c0ebfb6dcea49bf632d8880e04075335a132bf
2024-03-26 16:44:04 -07:00
Rebecca Turner 8e63eca912 Remove HintFmt::operator%
Change-Id: Ibcf1a7848b4b18ec9b0807628ff229079ae7a0fe
2024-03-26 15:40:05 -07:00
jade 61e21b2557 Delete hasPrefix and hasSuffix from the codebase
These now have equivalents in the standard lib in C++20. This change was
performed with a custom clang-tidy check which I will submit later.
Executed like so:

ninja -C build && run-clang-tidy -checks='-*,nix-*' -load=build/libnix-clang-tidy.so -p .. -fix ../tests | tee -a clang-tidy-result

Change-Id: I62679e315ff9e7ce72a40b91b79c3e9fc01b27e9
2024-03-17 20:17:19 -07:00
eldritch horrors b221a14f0a Merge pull request #9925 from 9999years/fmt-cleanup
Cleanup `fmt.hh`

(cherry picked from commit 47a1dbb4b8e7913cbb9b4d604728b912e76e4ca0)
Change-Id: Id076a45cb39652f437fe3f8bda10c310a9894777
2024-03-09 07:00:13 -07:00
eldritch horrors c208e918e5 fix: nlohmann::adl_serializer for std::optional (#9147)
This allows templates such as `NLOHMANN_DEFINE_TYPE_*` templates and other generators with things like `std::vector<std::optional<T>>`.

Co-authored-by: John Ericson <John.Ericson@Obsidian.Systems>
(cherry picked from commit 02bd821f2e71372d31bbe6700bd68086cc2ee70a)
Change-Id: I8b0ebcf2af4226610dadd565962f2d2327415a03
2024-03-04 07:11:25 +01:00
John Ericson f7f37035c8 Move tests to separate directories, and document
Today, with the tests inside a `tests` intermingled with the
corresponding library's source code, we have a few problems:

- We have to be careful that wildcards don't end up with tests being
  built as part of Nix proper, or test headers being installed as part
  of Nix proper.

- Tests in libraries but not executables is not right:

  - It means each executable runs the previous unit tests again, because
    it needs the libraries.

  - It doesn't work right on Windows, which doesn't want you to load a
    DLL just for the side global variable . It could be made to work
    with the dlopen equivalent, but that's gross!

This reorg solves these problems.

There is a remaining problem which is that sibbling headers (like
`hash.hh` the test header vs `hash.hh` the main `libnixutil` header) end
up shadowing each other. This PR doesn't solve that. That is left as
future work for a future PR.

Co-authored-by: Valentin Gagarin <valentin.gagarin@tweag.io>

(cherry picked from commit 91b6833686a6a6d9eac7f3f66393ec89ef1d3b57)
(cherry picked from commit a61e42adb528b3d40ce43e07c79368d779a8b624)
2023-12-01 13:05:03 -05:00