lix/src/libexpr/eval.cc
Eelco Dolstra 0c4c5c2020 * Quick hack to fix NIX-67: evaluation result differing if the Nix
expression resides in the store.
2006-10-10 21:23:35 +00:00

697 lines
21 KiB
C++

#include "eval.hh"
#include "parser.hh"
#include "hash.hh"
#include "util.hh"
#include "store.hh"
#include "nixexpr-ast.hh"
namespace nix {
EvalState::EvalState()
: normalForms(32768), primOps(128)
{
nrEvaluated = nrCached = 0;
initNixExprHelpers();
addPrimOps();
}
void EvalState::addPrimOp(const string & name,
unsigned int arity, PrimOp primOp)
{
primOps.set(toATerm(name), makePrimOpDef(arity, ATmakeBlob(0, (void *) primOp)));
}
/* Substitute an argument set into the body of a function. */
static Expr substArgs(EvalState & state,
Expr body, ATermList formals, Expr arg)
{
unsigned int nrFormals = ATgetLength(formals);
ATermMap subs(nrFormals);
/* Get the actual arguments and put them in the substitution. */
ATermMap args(128); /* !!! fix */
queryAllAttrs(arg, args);
for (ATermMap::const_iterator i = args.begin(); i != args.end(); ++i)
subs.set(i->key, i->value);
/* Get the formal arguments. */
ATermVector defsUsed;
ATermList recAttrs = ATempty;
for (ATermIterator i(formals); i; ++i) {
Expr name, def;
ValidValues valids2;
DefaultValue def2;
if (!matchFormal(*i, name, valids2, def2)) abort(); /* can't happen */
Expr value = subs[name];
if (value == 0) {
if (!matchDefaultValue(def2, def)) def = 0;
if (def == 0) throw TypeError(format("the argument named `%1%' required by the function is missing")
% aterm2String(name));
value = def;
defsUsed.push_back(name);
recAttrs = ATinsert(recAttrs, makeBind(name, def, makeNoPos()));
}
ATermList valids;
if (matchValidValues(valids2, valids)) {
value = evalExpr(state, value);
bool found = false;
for (ATermIterator j(valids); j; ++j) {
Expr v = evalExpr(state, *j);
if (value == v) {
found = true;
break;
}
}
if (!found) throw TypeError(format("the argument named `%1%' has an illegal value")
% aterm2String(name));
}
}
/* Make a recursive attribute set out of the (argument-name,
value) tuples. This is so that we can support default
parameters that refer to each other, e.g. ({x, y ? x + x}: y)
{x = "foo";} evaluates to "foofoo". */
if (defsUsed.size() != 0) {
for (ATermMap::const_iterator i = args.begin(); i != args.end(); ++i)
recAttrs = ATinsert(recAttrs, makeBind(i->key, i->value, makeNoPos()));
Expr rec = makeRec(recAttrs, ATempty);
for (ATermVector::iterator i = defsUsed.begin(); i != defsUsed.end(); ++i)
subs.set(*i, makeSelect(rec, *i));
}
if (subs.size() != nrFormals) {
/* One or more actual arguments were not declared as formal
arguments. Find out which. */
for (ATermIterator i(formals); i; ++i) {
Expr name; ATerm d1, d2;
if (!matchFormal(*i, name, d1, d2)) abort();
subs.remove(name);
}
throw TypeError(format("the function does not expect an argument named `%1%'")
% aterm2String(subs.begin()->key));
}
return substitute(Substitution(0, &subs), body);
}
/* Transform a mutually recursive set into a non-recursive set. Each
attribute is transformed into an expression that has all references
to attributes substituted with selection expressions on the
original set. E.g., e = `rec {x = f x y; y = x;}' becomes `{x = f
(e.x) (e.y); y = e.x;}'. */
ATerm expandRec(ATerm e, ATermList rbnds, ATermList nrbnds)
{
ATerm name;
Expr e2;
Pos pos;
/* Create the substitution list. */
ATermMap subs(ATgetLength(rbnds) + ATgetLength(nrbnds));
for (ATermIterator i(rbnds); i; ++i) {
if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
subs.set(name, makeSelect(e, name));
}
for (ATermIterator i(nrbnds); i; ++i) {
if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
subs.set(name, e2);
}
Substitution subs_(0, &subs);
/* Create the non-recursive set. */
ATermMap as(ATgetLength(rbnds) + ATgetLength(nrbnds));
for (ATermIterator i(rbnds); i; ++i) {
if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
as.set(name, makeAttrRHS(substitute(subs_, e2), pos));
}
/* Copy the non-recursive bindings. !!! inefficient */
for (ATermIterator i(nrbnds); i; ++i) {
if (!matchBind(*i, name, e2, pos)) abort(); /* can't happen */
as.set(name, makeAttrRHS(e2, pos));
}
return makeAttrs(as);
}
static Expr updateAttrs(Expr e1, Expr e2)
{
/* Note: e1 and e2 should be in normal form. */
ATermMap attrs(128); /* !!! */
queryAllAttrs(e1, attrs, true);
queryAllAttrs(e2, attrs, true);
return makeAttrs(attrs);
}
string evalString(EvalState & state, Expr e)
{
e = evalExpr(state, e);
ATerm s;
if (!matchStr(e, s))
throw TypeError(format("value is %1% while a string was expected") % showType(e));
return aterm2String(s);
}
Path evalPath(EvalState & state, Expr e)
{
e = evalExpr(state, e);
ATerm s;
if (!matchPath(e, s))
throw TypeError(format("value is %1% while a path was expected") % showType(e));
return aterm2String(s);
}
int evalInt(EvalState & state, Expr e)
{
e = evalExpr(state, e);
int i;
if (!matchInt(e, i))
throw TypeError(format("value is %1% while an integer was expected") % showType(e));
return i;
}
bool evalBool(EvalState & state, Expr e)
{
e = evalExpr(state, e);
if (e == eTrue) return true;
else if (e == eFalse) return false;
else throw TypeError(format("value is %1% while a boolean was expected") % showType(e));
}
ATermList evalList(EvalState & state, Expr e)
{
e = evalExpr(state, e);
ATermList list;
if (!matchList(e, list))
throw TypeError(format("value is %1% while a list was expected") % showType(e));
return list;
}
/* String concatenation and context nodes: in order to allow users to
write things like
"--with-freetype2-library=" + freetype + "/lib"
where `freetype' is a derivation, we automatically coerce
derivations into their output path (e.g.,
/nix/store/hashcode-freetype) in concatenations. However, if we do
this naively, we could introduce an undeclared dependency: when the
string is used in another derivation, that derivation would not
have an explicitly dependency on `freetype' in its inputDrvs
field. Thus `freetype' would not necessarily be built.
To prevent this, we wrap the string resulting from the
concatenation in a *context node*, like this:
Context([freetype],
Str("--with-freetype2-library=/nix/store/hashcode-freetype/lib"))
Thus the context is the list of all derivations used in the
computation of a value. These contexts are propagated through
further concatenations. In processBinding() in primops.cc, context
nodes are unwrapped and added to inputDrvs.
!!! Should the ordering of the context list have a canonical form?
!!! Contexts are not currently recognised in most places in the
evaluator. */
/* Coerce a value to a string, keeping track of contexts. */
string coerceToStringWithContext(EvalState & state,
ATermList & context, Expr e, bool & isPath)
{
isPath = false;
e = evalExpr(state, e);
bool isWrapped = false;
ATermList es;
ATerm e2;
if (matchContext(e, es, e2)) {
isWrapped = true;
e = e2;
context = ATconcat(es, context);
}
ATerm s;
if (matchStr(e, s) || matchUri(e, s))
return aterm2String(s);
if (matchPath(e, s)) {
isPath = true;
Path path = aterm2String(s);
if (isInStore(path) && !isWrapped) {
context = ATinsert(context, makePath(toATerm(toStorePath(path))));
}
return path;
}
if (matchAttrs(e, es)) {
ATermMap attrs(128); /* !!! */
queryAllAttrs(e, attrs, false);
Expr a = attrs.get(toATerm("type"));
if (a && evalString(state, a) == "derivation") {
a = attrs.get(toATerm("outPath"));
if (!a) throw TypeError("output path missing from derivation");
isPath = true;
context = ATinsert(context, e);
return evalPath(state, a);
}
}
throw TypeError(format("cannot coerce %1% to a string") % showType(e));
}
/* Wrap an expression in a context if the context is not empty. */
Expr wrapInContext(ATermList context, Expr e)
{
return context == ATempty ? e : makeContext(context, e);
}
static ATerm concatStrings(EvalState & state, const ATermVector & args)
{
ATermList context = ATempty;
std::ostringstream s;
bool isPath = false;
/* Note that if the first argument in the concatenation is a path,
then the result is also a path. */
for (ATermVector::const_iterator i = args.begin(); i != args.end(); ++i) {
bool isPath2;
s << coerceToStringWithContext(state, context, *i, isPath2);
if (i == args.begin()) isPath = isPath2;
}
return wrapInContext(context, isPath
? makePath(toATerm(canonPath(s.str())))
: makeStr(toATerm(s.str())));
}
Expr autoCallFunction(Expr e, const ATermMap & args)
{
ATermList formals;
ATerm body, pos;
if (matchFunction(e, formals, body, pos)) {
ATermMap actualArgs(128);
for (ATermIterator i(formals); i; ++i) {
Expr name, def, value; ATerm values, def2;
if (!matchFormal(*i, name, values, def2)) abort();
if ((value = args.get(name)))
actualArgs.set(name, makeAttrRHS(value, makeNoPos()));
else if (!matchDefaultValue(def2, def))
throw TypeError(format("cannot auto-call a function that has an argument without a default value (`%1%')")
% aterm2String(name));
}
e = makeCall(e, makeAttrs(actualArgs));
}
return e;
}
Expr evalExpr2(EvalState & state, Expr e)
{
Expr e1, e2, e3, e4;
ATerm name, pos;
AFun sym = ATgetAFun(e);
/* Normal forms. */
if (sym == symStr ||
sym == symPath ||
sym == symUri ||
sym == symNull ||
sym == symInt ||
sym == symBool ||
sym == symFunction ||
sym == symFunction1 ||
sym == symAttrs ||
sym == symList ||
sym == symPrimOp ||
sym == symContext)
return e;
/* The `Closed' constructor is just a way to prevent substitutions
into expressions not containing free variables. */
if (matchClosed(e, e1))
return evalExpr(state, e1);
/* Any encountered variables must be primops (since undefined
variables are detected after parsing). */
if (matchVar(e, name)) {
ATerm primOp = state.primOps.get(name);
if (!primOp)
throw EvalError(format("impossible: undefined variable `%1%'") % aterm2String(name));
int arity;
ATermBlob fun;
if (!matchPrimOpDef(primOp, arity, fun)) abort();
if (arity == 0)
return ((PrimOp) ATgetBlobData(fun)) (state, ATermVector());
else
return makePrimOp(arity, fun, ATempty);
}
/* Function application. */
if (matchCall(e, e1, e2)) {
ATermList formals;
ATerm pos;
/* Evaluate the left-hand side. */
e1 = evalExpr(state, e1);
/* Is it a primop or a function? */
int arity;
ATermBlob fun;
ATermList args;
if (matchPrimOp(e1, arity, fun, args)) {
args = ATinsert(args, e2);
if (ATgetLength(args) == arity) {
/* Put the arguments in a vector in reverse (i.e.,
actual) order. */
ATermVector args2(arity);
for (ATermIterator i(args); i; ++i)
args2[--arity] = *i;
return ((PrimOp) ATgetBlobData((ATermBlob) fun))
(state, args2);
} else
/* Need more arguments, so propagate the primop. */
return makePrimOp(arity, fun, args);
}
else if (matchFunction(e1, formals, e4, pos)) {
e2 = evalExpr(state, e2);
try {
return evalExpr(state, substArgs(state, e4, formals, e2));
} catch (Error & e) {
e.addPrefix(format("while evaluating the function at %1%:\n")
% showPos(pos));
throw;
}
}
else if (matchFunction1(e1, name, e4, pos)) {
try {
ATermMap subs(1);
subs.set(name, e2);
return evalExpr(state, substitute(Substitution(0, &subs), e4));
} catch (Error & e) {
e.addPrefix(format("while evaluating the function at %1%:\n")
% showPos(pos));
throw;
}
}
else throw TypeError(
format("the left-hand side of the function call is neither a function nor a primop (built-in operation) but %1%")
% showType(e1));
}
/* Attribute selection. */
if (matchSelect(e, e1, name)) {
ATerm pos;
string s1 = aterm2String(name);
Expr a = queryAttr(evalExpr(state, e1), s1, pos);
if (!a) throw EvalError(format("attribute `%1%' missing") % s1);
try {
return evalExpr(state, a);
} catch (Error & e) {
e.addPrefix(format("while evaluating the attribute `%1%' at %2%:\n")
% s1 % showPos(pos));
throw;
}
}
/* Mutually recursive sets. */
ATermList rbnds, nrbnds;
if (matchRec(e, rbnds, nrbnds))
return expandRec(e, rbnds, nrbnds);
/* Conditionals. */
if (matchIf(e, e1, e2, e3)) {
if (evalBool(state, e1))
return evalExpr(state, e2);
else
return evalExpr(state, e3);
}
/* Assertions. */
if (matchAssert(e, e1, e2, pos)) {
if (!evalBool(state, e1))
throw AssertionError(format("assertion failed at %1%") % showPos(pos));
return evalExpr(state, e2);
}
/* Withs. */
if (matchWith(e, e1, e2, pos)) {
ATermMap attrs(128); /* !!! */
try {
e1 = evalExpr(state, e1);
queryAllAttrs(e1, attrs);
} catch (Error & e) {
e.addPrefix(format("while evaluating the `with' definitions at %1%:\n")
% showPos(pos));
throw;
}
try {
e2 = substitute(Substitution(0, &attrs), e2);
checkVarDefs(state.primOps, e2);
return evalExpr(state, e2);
} catch (Error & e) {
e.addPrefix(format("while evaluating the `with' body at %1%:\n")
% showPos(pos));
throw;
}
}
/* Generic equality/inequality. Note that the behaviour on
composite data (lists, attribute sets) and functions is
undefined, since the subterms of those terms are not evaluated.
However, we don't want to make (==) strict, because that would
make operations like `big_derivation == null' very slow (unless
we were to evaluate them side-by-side). */
if (matchOpEq(e, e1, e2))
return makeBool(evalExpr(state, e1) == evalExpr(state, e2));
if (matchOpNEq(e, e1, e2))
return makeBool(evalExpr(state, e1) != evalExpr(state, e2));
/* Negation. */
if (matchOpNot(e, e1))
return makeBool(!evalBool(state, e1));
/* Implication. */
if (matchOpImpl(e, e1, e2))
return makeBool(!evalBool(state, e1) || evalBool(state, e2));
/* Conjunction (logical AND). */
if (matchOpAnd(e, e1, e2))
return makeBool(evalBool(state, e1) && evalBool(state, e2));
/* Disjunction (logical OR). */
if (matchOpOr(e, e1, e2))
return makeBool(evalBool(state, e1) || evalBool(state, e2));
/* Attribute set update (//). */
if (matchOpUpdate(e, e1, e2))
return updateAttrs(evalExpr(state, e1), evalExpr(state, e2));
/* Attribute existence test (?). */
if (matchOpHasAttr(e, e1, name)) {
ATermMap attrs(128); /* !!! */
queryAllAttrs(evalExpr(state, e1), attrs);
return makeBool(attrs.get(name) != 0);
}
/* String or path concatenation. */
ATermList es = ATempty;
if (matchOpPlus(e, e1, e2) || matchConcatStrings(e, es)) {
ATermVector args;
if (matchOpPlus(e, e1, e2)) {
args.push_back(e1);
args.push_back(e2);
} else
for (ATermIterator i(es); i; ++i) args.push_back(*i);
try {
return concatStrings(state, args);
} catch (Error & e) {
e.addPrefix(format("in a string concatenation:\n"));
throw;
}
}
/* Backwards compatability: subpath operator (~). */
if (matchSubPath(e, e1, e2)) {
static bool haveWarned = false;
warnOnce(haveWarned, "the subpath operator (~) is deprecated, use string concatenation (+) instead");
ATermList context = ATempty;
bool dummy;
string s1 = coerceToStringWithContext(state, context, e1, dummy);
string s2 = coerceToStringWithContext(state, context, e2, dummy);
return wrapInContext(context, makePath(toATerm(canonPath(s1 + "/" + s2))));
}
/* List concatenation. */
if (matchOpConcat(e, e1, e2)) {
try {
ATermList l1 = evalList(state, e1);
ATermList l2 = evalList(state, e2);
return makeList(ATconcat(l1, l2));
} catch (Error & e) {
e.addPrefix(format("in a list concatenation:\n"));
throw;
}
}
/* Barf. */
throw badTerm("invalid expression", e);
}
Expr evalExpr(EvalState & state, Expr e)
{
checkInterrupt();
startNest(nest, lvlVomit,
format("evaluating expression: %1%") % e);
state.nrEvaluated++;
/* Consult the memo table to quickly get the normal form of
previously evaluated expressions. */
Expr nf = state.normalForms.get(e);
if (nf) {
if (nf == makeBlackHole())
throw EvalError("infinite recursion encountered");
state.nrCached++;
return nf;
}
/* Otherwise, evaluate and memoize. */
state.normalForms.set(e, makeBlackHole());
try {
nf = evalExpr2(state, e);
} catch (Error & err) {
debug("removing black hole");
state.normalForms.remove(e);
throw;
}
state.normalForms.set(e, nf);
return nf;
}
Expr evalFile(EvalState & state, const Path & path)
{
startNest(nest, lvlTalkative, format("evaluating file `%1%'") % path);
Expr e = parseExprFromFile(state, path);
try {
return evalExpr(state, e);
} catch (Error & e) {
e.addPrefix(format("while evaluating the file `%1%':\n")
% path);
throw;
}
}
Expr strictEvalExpr(EvalState & state, Expr e, bool canonicalise)
{
e = evalExpr(state, e);
ATermList as;
if (matchAttrs(e, as)) {
ATermList as2 = ATempty;
for (ATermIterator i(as); i; ++i) {
ATerm name; Expr e; ATerm pos;
if (!matchBind(*i, name, e, pos)) abort(); /* can't happen */
as2 = ATinsert(as2, makeBind(name, strictEvalExpr(state, e, canonicalise),
canonicalise ? makeNoPos() : pos));
}
/* !!! sort attributes if canonicalise == true */
return makeAttrs(ATreverse(as2));
}
ATermList es;
if (matchList(e, es)) {
ATermList es2 = ATempty;
for (ATermIterator i(es); i; ++i)
es2 = ATinsert(es2, strictEvalExpr(state, *i, canonicalise));
return makeList(ATreverse(es2));
}
ATermList formals;
ATerm body, pos;
if (matchFunction(e, formals, body, pos)) {
ATermList formals2 = ATempty;
for (ATermIterator i(formals); i; ++i) {
Expr name; ValidValues valids; ATerm dummy;
if (!matchFormal(*i, name, valids, dummy)) abort();
ATermList valids2;
if (matchValidValues(valids, valids2)) {
ATermList valids3 = ATempty;
for (ATermIterator j(valids2); j; ++j)
valids3 = ATinsert(valids3, strictEvalExpr(state, *j, canonicalise));
valids = makeValidValues(ATreverse(valids3));
}
formals2 = ATinsert(formals2, makeFormal(name, valids, dummy));
}
return makeFunction(ATreverse(formals2), body,
canonicalise ? makeNoPos() : pos);
}
return e;
}
/* Yes, this is a really bad idea... */
extern "C" {
unsigned long AT_calcAllocatedSize();
}
void printEvalStats(EvalState & state)
{
bool showStats = getEnv("NIX_SHOW_STATS", "0") != "0";
printMsg(showStats ? lvlInfo : lvlDebug,
format("evaluated %1% expressions, %2% cache hits, %3%%% efficiency, used %4% ATerm bytes")
% state.nrEvaluated % state.nrCached
% ((float) state.nrCached / (float) state.nrEvaluated * 100)
% AT_calcAllocatedSize());
if (showStats)
printATermMapStats();
}
}