mirror of
https://github.com/NixOS/nix
synced 2024-09-19 10:50:24 -04:00
8c0590fa32
Thunks are now overwritten by a helper function `Value::finishValue(newType, payload)` (where `payload` is the original anonymous union inside `Value`). This helps to ensure we never update a value elsewhere, since that would be incompatible with parallel evaluation (i.e. after a value has transitioned from being a thunk to being a non-thunk, it should be immutable). There were two places where this happened: `Value::mkString()` and `ExprAttrs::eval()`. This PR also adds a bunch of accessor functions for value contents, like `Value::integer()` to access the integer field in the union.
143 lines
3.5 KiB
C++
143 lines
3.5 KiB
C++
#pragma once
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///@file
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#include "print.hh"
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#include "eval.hh"
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#include "eval-error.hh"
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namespace nix {
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/**
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* Note: Various places expect the allocated memory to be zeroed.
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*/
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[[gnu::always_inline]]
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inline void * allocBytes(size_t n)
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{
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void * p;
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#if HAVE_BOEHMGC
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p = GC_MALLOC(n);
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#else
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p = calloc(n, 1);
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#endif
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if (!p) throw std::bad_alloc();
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return p;
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}
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[[gnu::always_inline]]
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Value * EvalState::allocValue()
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{
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#if HAVE_BOEHMGC
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/* We use the boehm batch allocator to speed up allocations of Values (of which there are many).
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GC_malloc_many returns a linked list of objects of the given size, where the first word
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of each object is also the pointer to the next object in the list. This also means that we
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have to explicitly clear the first word of every object we take. */
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if (!*valueAllocCache) {
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*valueAllocCache = GC_malloc_many(sizeof(Value));
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if (!*valueAllocCache) throw std::bad_alloc();
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}
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/* GC_NEXT is a convenience macro for accessing the first word of an object.
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Take the first list item, advance the list to the next item, and clear the next pointer. */
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void * p = *valueAllocCache;
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*valueAllocCache = GC_NEXT(p);
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GC_NEXT(p) = nullptr;
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#else
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void * p = allocBytes(sizeof(Value));
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#endif
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nrValues++;
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return (Value *) p;
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}
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[[gnu::always_inline]]
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Env & EvalState::allocEnv(size_t size)
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{
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nrEnvs++;
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nrValuesInEnvs += size;
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Env * env;
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#if HAVE_BOEHMGC
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if (size == 1) {
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/* see allocValue for explanations. */
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if (!*env1AllocCache) {
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*env1AllocCache = GC_malloc_many(sizeof(Env) + sizeof(Value *));
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if (!*env1AllocCache) throw std::bad_alloc();
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}
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void * p = *env1AllocCache;
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*env1AllocCache = GC_NEXT(p);
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GC_NEXT(p) = nullptr;
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env = (Env *) p;
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} else
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#endif
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env = (Env *) allocBytes(sizeof(Env) + size * sizeof(Value *));
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/* We assume that env->values has been cleared by the allocator; maybeThunk() and lookupVar fromWith expect this. */
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return *env;
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}
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[[gnu::always_inline]]
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void EvalState::forceValue(Value & v, const PosIdx pos)
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{
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if (v.isThunk()) {
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Env * env = v.payload.thunk.env;
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Expr * expr = v.payload.thunk.expr;
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try {
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v.mkBlackhole();
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//checkInterrupt();
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expr->eval(*this, *env, v);
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} catch (...) {
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v.mkThunk(env, expr);
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tryFixupBlackHolePos(v, pos);
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throw;
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}
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}
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else if (v.isApp())
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callFunction(*v.payload.app.left, *v.payload.app.right, v, pos);
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}
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[[gnu::always_inline]]
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inline void EvalState::forceAttrs(Value & v, const PosIdx pos, std::string_view errorCtx)
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{
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forceAttrs(v, [&]() { return pos; }, errorCtx);
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}
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template <typename Callable>
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[[gnu::always_inline]]
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inline void EvalState::forceAttrs(Value & v, Callable getPos, std::string_view errorCtx)
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{
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PosIdx pos = getPos();
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forceValue(v, pos);
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if (v.type() != nAttrs) {
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error<TypeError>(
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"expected a set but found %1%: %2%",
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showType(v),
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ValuePrinter(*this, v, errorPrintOptions)
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).withTrace(pos, errorCtx).debugThrow();
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}
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}
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[[gnu::always_inline]]
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inline void EvalState::forceList(Value & v, const PosIdx pos, std::string_view errorCtx)
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{
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forceValue(v, pos);
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if (!v.isList()) {
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error<TypeError>(
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"expected a list but found %1%: %2%",
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showType(v),
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ValuePrinter(*this, v, errorPrintOptions)
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).withTrace(pos, errorCtx).debugThrow();
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}
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}
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}
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