eldritch horrors
80654b84b6
thunk values are shareable, and we can represent invalid/uninitialized values with a special bit pattern that makes no sense otherwise. there is no need to keep allocating values on the heap, instead we can treat values like reference-counted smart pointers to heap objects, which in turn lets us save a lot of allocations and, ultimately, gc heap space. compared to our baseline (main of 2025-09-27) we save 15%+ memory on a system rebuild and 17% on nix search. eval time regresses by ~3% for a system rebuild, while nix search is 7% faster. further optimization is probably possible (but for now this will just have to be good enough). Change-Id: Ib6c47acdbe2fac4f76a83c2269f16f30ef66b2e1
113 lines
4.1 KiB
C++
113 lines
4.1 KiB
C++
#include "lix/libexpr/primops.hh"
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#include "lix/libexpr/eval-settings.hh"
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#include "lix/libfetchers/fetchers.hh"
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#include "lix/libutil/url-parts.hh"
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namespace nix {
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static void prim_fetchMercurial(EvalState & state, Value * * args, Value & v)
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{
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std::string url;
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std::optional<Hash> rev;
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std::optional<std::string> ref;
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std::string_view name = "source";
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NixStringContext context;
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state.forceValue(*args[0], noPos);
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if (args[0]->type() == nAttrs) {
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for (auto & attr : *args[0]->attrs()) {
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std::string_view n(state.ctx.symbols[attr.name]);
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if (n == "url")
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url = state
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.coerceToString(
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attr.pos,
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attr.value,
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context,
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"while evaluating the `url` attribute passed to "
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"builtins.fetchMercurial",
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StringCoercionMode::Strict,
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false
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)
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.toOwned();
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else if (n == "rev") {
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// Ugly: unlike fetchGit, here the "rev" attribute can
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// be both a revision or a branch/tag name.
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auto value = state.forceStringNoCtx(
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attr.value,
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attr.pos,
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"while evaluating the `rev` attribute passed to builtins.fetchMercurial"
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);
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if (std::regex_match(value.begin(), value.end(), revRegex)) {
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rev = Hash::parseAny(value, HashType::SHA1);
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} else
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ref = value;
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}
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else if (n == "name")
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name = state.forceStringNoCtx(
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attr.value,
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attr.pos,
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"while evaluating the `name` attribute passed to builtins.fetchMercurial"
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);
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else {
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state.ctx.errors
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.make<EvalError>(
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"unsupported argument '%s' to 'fetchMercurial'",
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state.ctx.symbols[attr.name]
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)
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.atPos(attr.pos)
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.debugThrow();
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}
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}
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if (url.empty())
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state.ctx.errors.make<EvalError>("'url' argument required").debugThrow();
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} else
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url = state.coerceToString(noPos, *args[0], context,
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"while evaluating the first argument passed to builtins.fetchMercurial",
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StringCoercionMode::Strict, false).toOwned();
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// FIXME: git externals probably can be used to bypass the URI
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// whitelist. Ah well.
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state.ctx.paths.checkURI(url);
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if (evalSettings.pureEval && !rev)
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throw Error("in pure evaluation mode, 'fetchMercurial' requires a Mercurial revision");
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fetchers::Attrs attrs;
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attrs.insert_or_assign("type", "hg");
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attrs.insert_or_assign("url", url.find("://") != std::string::npos ? url : "file://" + url);
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attrs.insert_or_assign("name", std::string(name));
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if (ref) attrs.insert_or_assign("ref", *ref);
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if (rev) attrs.insert_or_assign("rev", rev->gitRev());
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auto input = fetchers::Input::fromAttrs(std::move(attrs));
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// FIXME: use name
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auto [tree, input2] = state.aio.blockOn(input.fetch(state.ctx.store));
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auto attrs2 = state.ctx.buildBindings(8);
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state.ctx.paths.mkStorePathString(tree.storePath, attrs2.alloc(state.ctx.s.outPath));
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if (input2.getRef())
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attrs2.alloc("branch").mkString(*input2.getRef());
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// Backward compatibility: set 'rev' to
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// 0000000000000000000000000000000000000000 for a dirty tree.
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auto rev2 = input2.getRev().value_or(Hash(HashType::SHA1));
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attrs2.alloc("rev").mkString(rev2.gitRev());
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attrs2.alloc("shortRev").mkString(rev2.gitRev().substr(0, 12));
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if (auto revCount = input2.getRevCount())
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attrs2.alloc("revCount").mkInt(*revCount);
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v.mkAttrs(attrs2);
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state.ctx.paths.allowPath(tree.storePath);
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}
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static RegisterPrimOp r_fetchMercurial({
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.name = "fetchMercurial",
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.arity = 1,
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.fun = prim_fetchMercurial
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});
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}
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