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store Symbols in a table as well, like positions

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this slightly increases the amount of memory used for any given symbol, but this
increase is more than made up for if the symbol is referenced more than once in
the EvalState that holds it. on average every symbol should be referenced at
least twice (once to introduce a binding, once to use it), so we expect no
increase in memory on average.

symbol tables are limited to 2³² entries like position tables, and similar
arguments apply to why overflow is not likely: 2³² symbols would require as many
string instances (at 24 bytes each) and map entries (at 24 bytes or more each,
assuming that the map holds on average at most one item per bucket as the docs
say). a full symbol table would require at least 192GB of memory just for
symbols, which is well out of reach. (an ofborg eval of nixpks today creates
less than a million symbols!)
This commit is contained in:
pennae 2022-03-05 14:40:24 +01:00
parent 00a3280232
commit 8775be3393
32 changed files with 525 additions and 448 deletions
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84
src/libexpr/eval.cc
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@ -96,7 +96,8 @@ RootValue allocRootValue(Value * v)
}
void Value::print(std::ostream & str, std::set<const void *> * seen) const
void Value::print(const SymbolTable & symbols, std::ostream & str,
std::set<const void *> * seen) const
{
checkInterrupt();
@ -129,9 +130,9 @@ void Value::print(std::ostream & str, std::set<const void *> * seen) const
str << "«repeated»";
else {
str << "{ ";
for (auto & i : attrs->lexicographicOrder()) {
str << i->name << " = ";
i->value->print(str, seen);
for (auto & i : attrs->lexicographicOrder(symbols)) {
str << symbols[i->name] << " = ";
i->value->print(symbols, str, seen);
str << "; ";
}
str << "}";
@ -146,7 +147,7 @@ void Value::print(std::ostream & str, std::set<const void *> * seen) const
else {
str << "[ ";
for (auto v2 : listItems()) {
v2->print(str, seen);
v2->print(symbols, str, seen);
str << " ";
}
str << "]";
@ -177,17 +178,18 @@ void Value::print(std::ostream & str, std::set<const void *> * seen) const
}
void Value::print(std::ostream & str, bool showRepeated) const
void Value::print(const SymbolTable & symbols, std::ostream & str, bool showRepeated) const
{
std::set<const void *> seen;
print(str, showRepeated ? nullptr : &seen);
print(symbols, str, showRepeated ? nullptr : &seen);
}
std::ostream & operator << (std::ostream & str, const Value & v)
std::string printValue(const EvalState & state, const Value & v)
{
v.print(str, false);
return str;
std::ostringstream out;
v.print(state.symbols, out);
return out.str();
}
@ -306,9 +308,9 @@ static BoehmGCStackAllocator boehmGCStackAllocator;
#endif
static Symbol getName(const AttrName & name, EvalState & state, Env & env)
static SymbolIdx getName(const AttrName & name, EvalState & state, Env & env)
{
if (name.symbol.set()) {
if (name.symbol) {
return name.symbol;
} else {
Value nameValue;
@ -639,7 +641,7 @@ Value * EvalState::addPrimOp(const std::string & name,
size_t arity, PrimOpFun primOp)
{
auto name2 = name.substr(0, 2) == "__" ? name.substr(2) : name;
Symbol sym = symbols.create(name2);
auto sym = symbols.create(name2);
/* Hack to make constants lazy: turn them into a application of
the primop to a dummy value. */
@ -673,7 +675,7 @@ Value * EvalState::addPrimOp(PrimOp && primOp)
return addConstant(primOp.name, v);
}
Symbol envName = symbols.create(primOp.name);
auto envName = symbols.create(primOp.name);
if (hasPrefix(primOp.name, "__"))
primOp.name = primOp.name.substr(2);
@ -767,11 +769,11 @@ void EvalState::throwEvalError(const PosIdx pos, const char * s, const std::stri
});
}
void EvalState::throwEvalError(const PosIdx p1, const char * s, const Symbol & sym, const PosIdx p2) const
void EvalState::throwEvalError(const PosIdx p1, const char * s, const SymbolIdx sym, const PosIdx p2) const
{
// p1 is where the error occurred; p2 is a position mentioned in the message.
throw EvalError({
.msg = hintfmt(s, sym, positions[p2]),
.msg = hintfmt(s, symbols[sym], positions[p2]),
.errPos = positions[p1]
});
}
@ -785,19 +787,19 @@ void EvalState::throwTypeError(const PosIdx pos, const char * s) const
}
void EvalState::throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun,
const Symbol & s2) const
const SymbolIdx s2) const
{
throw TypeError({
.msg = hintfmt(s, fun.showNamePos(positions), s2),
.msg = hintfmt(s, fun.showNamePos(*this), symbols[s2]),
.errPos = positions[pos]
});
}
void EvalState::throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const ExprLambda & fun, const Symbol & s2) const
const ExprLambda & fun, const SymbolIdx s2) const
{
throw TypeError(ErrorInfo {
.msg = hintfmt(s, fun.showNamePos(positions), s2),
.msg = hintfmt(s, fun.showNamePos(*this), symbols[s2]),
.errPos = positions[pos],
.suggestions = suggestions,
});
@ -901,7 +903,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
return j->value;
}
if (!env->prevWith)
throwUndefinedVarError(var.pos, "undefined variable '%1%'", var.name);
throwUndefinedVarError(var.pos, "undefined variable '%1%'", symbols[var.name]);
for (size_t l = env->prevWith; l; --l, env = env->up) ;
}
}
@ -1187,7 +1189,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
if (nameVal.type() == nNull)
continue;
state.forceStringNoCtx(nameVal);
Symbol nameSym = state.symbols.create(nameVal.string.s);
auto nameSym = state.symbols.create(nameVal.string.s);
Bindings::iterator j = v.attrs->find(nameSym);
if (j != v.attrs->end())
state.throwEvalError(i.pos, "dynamic attribute '%1%' already defined at %2%", nameSym, j->pos);
@ -1243,10 +1245,12 @@ static std::string showAttrPath(EvalState & state, Env & env, const AttrPath & a
for (auto & i : attrPath) {
if (!first) out << '.'; else first = false;
try {
out << getName(i, state, env);
out << state.symbols[getName(i, state, env)];
} catch (Error & e) {
assert(!i.symbol.set());
out << "\"${" << *i.expr << "}\"";
assert(!i.symbol);
out << "\"${";
i.expr->show(state.symbols, out);
out << "}\"";
}
}
return out.str();
@ -1266,7 +1270,7 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
for (auto & i : attrPath) {
state.nrLookups++;
Bindings::iterator j;
Symbol name = getName(i, state, env);
auto name = getName(i, state, env);
if (def) {
state.forceValue(*vAttrs, pos);
if (vAttrs->type() != nAttrs ||
@ -1280,11 +1284,11 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
if ((j = vAttrs->attrs->find(name)) == vAttrs->attrs->end()) {
std::set<std::string> allAttrNames;
for (auto & attr : *vAttrs->attrs)
allAttrNames.insert(attr.name);
allAttrNames.insert(state.symbols[attr.name]);
state.throwEvalError(
pos,
Suggestions::bestMatches(allAttrNames, name),
"attribute '%1%' missing", name);
Suggestions::bestMatches(allAttrNames, state.symbols[name]),
"attribute '%1%' missing", state.symbols[name]);
}
}
vAttrs = j->value;
@ -1316,7 +1320,7 @@ void ExprOpHasAttr::eval(EvalState & state, Env & env, Value & v)
for (auto & i : attrPath) {
state.forceValue(*vAttrs, noPos);
Bindings::iterator j;
Symbol name = getName(i, state, env);
auto name = getName(i, state, env);
if (vAttrs->type() != nAttrs ||
(j = vAttrs->attrs->find(name)) == vAttrs->attrs->end())
{
@ -1366,7 +1370,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
ExprLambda & lambda(*vCur.lambda.fun);
auto size =
(!lambda.arg.set() ? 0 : 1) +
(!lambda.arg ? 0 : 1) +
(lambda.hasFormals() ? lambda.formals->formals.size() : 0);
Env & env2(allocEnv(size));
env2.up = vCur.lambda.env;
@ -1379,7 +1383,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
else {
forceAttrs(*args[0], pos);
if (lambda.arg.set())
if (lambda.arg)
env2.values[displ++] = args[0];
/* For each formal argument, get the actual argument. If
@ -1407,10 +1411,10 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
if (!lambda.formals->has(i.name)) {
std::set<std::string> formalNames;
for (auto & formal : lambda.formals->formals)
formalNames.insert(formal.name);
formalNames.insert(symbols[formal.name]);
throwTypeError(
pos,
Suggestions::bestMatches(formalNames, i.name),
Suggestions::bestMatches(formalNames, symbols[i.name]),
"%1% called with unexpected argument '%2%'",
lambda,
i.name);
@ -1428,8 +1432,8 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
} catch (Error & e) {
if (loggerSettings.showTrace.get()) {
addErrorTrace(e, lambda.pos, "while evaluating %s",
(lambda.name.set()
? "'" + (const std::string &) lambda.name + "'"
(lambda.name
? concatStrings("'", symbols[lambda.name], "'")
: "anonymous lambda"));
addErrorTrace(e, pos, "from call site%s", "");
}
@ -1578,7 +1582,7 @@ void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
Nix attempted to evaluate a function as a top level expression; in
this case it must have its arguments supplied either by default
values, or passed explicitly with '--arg' or '--argstr'. See
https://nixos.org/manual/nix/stable/#ss-functions.)", i.name);
https://nixos.org/manual/nix/stable/#ss-functions.)", symbols[i.name]);
}
}
@ -1610,7 +1614,7 @@ void ExprAssert::eval(EvalState & state, Env & env, Value & v)
{
if (!state.evalBool(env, cond, pos)) {
std::ostringstream out;
cond->show(out);
cond->show(state.symbols, out);
state.throwAssertionError(pos, "assertion '%1%' failed", out.str());
}
body->eval(state, env, v);
@ -1844,7 +1848,7 @@ void EvalState::forceValueDeep(Value & v)
try {
recurse(*i.value);
} catch (Error & e) {
addErrorTrace(e, i.pos, "while evaluating the attribute '%1%'", i.name);
addErrorTrace(e, i.pos, "while evaluating the attribute '%1%'", symbols[i.name]);
throw;
}
}
@ -2267,7 +2271,7 @@ void EvalState::printStats()
auto list = topObj.list("functions");
for (auto & i : functionCalls) {
auto obj = list.object();
if (i.first->name.set())
if (i.first->name)
obj.attr("name", (const std::string &) i.first->name);
else
obj.attr("name", nullptr);