Force all Pos* to be non-null

This fixes a class of crashes and introduces ptr<T> to make the
code robust against this failure mode going forward.

Thanks regnat for the idea of a ref<T> without overhead!

Closes #4895
Closes #4893
Closes #5127
Closes #5113
This commit is contained in:
Robert Hensing 2021-08-29 18:09:13 +02:00
parent af94b54db3
commit f10465774f
7 changed files with 65 additions and 22 deletions

View file

@ -17,8 +17,8 @@ struct Attr
{ {
Symbol name; Symbol name;
Value * value; Value * value;
Pos * pos; ptr<Pos> pos;
Attr(Symbol name, Value * value, Pos * pos = &noPos) Attr(Symbol name, Value * value, ptr<Pos> pos = ptr(&noPos))
: name(name), value(value), pos(pos) { }; : name(name), value(value), pos(pos) { };
Attr() : pos(&noPos) { }; Attr() : pos(&noPos) { };
bool operator < (const Attr & a) const bool operator < (const Attr & a) const
@ -35,13 +35,13 @@ class Bindings
{ {
public: public:
typedef uint32_t size_t; typedef uint32_t size_t;
Pos *pos; ptr<Pos> pos;
private: private:
size_t size_, capacity_; size_t size_, capacity_;
Attr attrs[0]; Attr attrs[0];
Bindings(size_t capacity) : size_(0), capacity_(capacity) { } Bindings(size_t capacity) : pos(&noPos), size_(0), capacity_(capacity) { }
Bindings(const Bindings & bindings) = delete; Bindings(const Bindings & bindings) = delete;
public: public:

View file

@ -770,7 +770,7 @@ inline Value * EvalState::lookupVar(Env * env, const ExprVar & var, bool noEval)
} }
Bindings::iterator j = env->values[0]->attrs->find(var.name); Bindings::iterator j = env->values[0]->attrs->find(var.name);
if (j != env->values[0]->attrs->end()) { if (j != env->values[0]->attrs->end()) {
if (countCalls && j->pos) attrSelects[*j->pos]++; if (countCalls) attrSelects[*j->pos]++;
return j->value; return j->value;
} }
if (!env->prevWith) if (!env->prevWith)
@ -825,9 +825,9 @@ void EvalState::mkThunk_(Value & v, Expr * expr)
} }
void EvalState::mkPos(Value & v, Pos * pos) void EvalState::mkPos(Value & v, ptr<Pos> pos)
{ {
if (pos && pos->file.set()) { if (pos->file.set()) {
mkAttrs(v, 3); mkAttrs(v, 3);
mkString(*allocAttr(v, sFile), pos->file); mkString(*allocAttr(v, sFile), pos->file);
mkInt(*allocAttr(v, sLine), pos->line); mkInt(*allocAttr(v, sLine), pos->line);
@ -1027,7 +1027,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
} else } else
vAttr = i.second.e->maybeThunk(state, i.second.inherited ? env : env2); vAttr = i.second.e->maybeThunk(state, i.second.inherited ? env : env2);
env2.values[displ++] = vAttr; env2.values[displ++] = vAttr;
v.attrs->push_back(Attr(i.first, vAttr, &i.second.pos)); v.attrs->push_back(Attr(i.first, vAttr, ptr(&i.second.pos)));
} }
/* If the rec contains an attribute called `__overrides', then /* If the rec contains an attribute called `__overrides', then
@ -1059,7 +1059,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
else else
for (auto & i : attrs) for (auto & i : attrs)
v.attrs->push_back(Attr(i.first, i.second.e->maybeThunk(state, env), &i.second.pos)); v.attrs->push_back(Attr(i.first, i.second.e->maybeThunk(state, env), ptr(&i.second.pos)));
/* Dynamic attrs apply *after* rec and __overrides. */ /* Dynamic attrs apply *after* rec and __overrides. */
for (auto & i : dynamicAttrs) { for (auto & i : dynamicAttrs) {
@ -1076,11 +1076,11 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
i.valueExpr->setName(nameSym); i.valueExpr->setName(nameSym);
/* Keep sorted order so find can catch duplicates */ /* Keep sorted order so find can catch duplicates */
v.attrs->push_back(Attr(nameSym, i.valueExpr->maybeThunk(state, *dynamicEnv), &i.pos)); v.attrs->push_back(Attr(nameSym, i.valueExpr->maybeThunk(state, *dynamicEnv), ptr(&i.pos)));
v.attrs->sort(); // FIXME: inefficient v.attrs->sort(); // FIXME: inefficient
} }
v.attrs->pos = &pos; v.attrs->pos = ptr(&pos);
} }
@ -1138,7 +1138,7 @@ static string showAttrPath(EvalState & state, Env & env, const AttrPath & attrPa
void ExprSelect::eval(EvalState & state, Env & env, Value & v) void ExprSelect::eval(EvalState & state, Env & env, Value & v)
{ {
Value vTmp; Value vTmp;
Pos * pos2 = 0; ptr<Pos> pos2(&noPos);
Value * vAttrs = &vTmp; Value * vAttrs = &vTmp;
e->eval(state, env, vTmp); e->eval(state, env, vTmp);
@ -1164,13 +1164,13 @@ void ExprSelect::eval(EvalState & state, Env & env, Value & v)
} }
vAttrs = j->value; vAttrs = j->value;
pos2 = j->pos; pos2 = j->pos;
if (state.countCalls && pos2) state.attrSelects[*pos2]++; if (state.countCalls) state.attrSelects[*pos2]++;
} }
state.forceValue(*vAttrs, ( pos2 != NULL ? *pos2 : this->pos ) ); state.forceValue(*vAttrs, (*pos2 != noPos ? *pos2 : this->pos ) );
} catch (Error & e) { } catch (Error & e) {
if (pos2 && pos2->file != state.sDerivationNix) if (*pos2 != noPos && pos2->file != state.sDerivationNix)
addErrorTrace(e, *pos2, "while evaluating the attribute '%1%'", addErrorTrace(e, *pos2, "while evaluating the attribute '%1%'",
showAttrPath(state, env, attrPath)); showAttrPath(state, env, attrPath));
throw; throw;
@ -1616,7 +1616,7 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
void ExprPos::eval(EvalState & state, Env & env, Value & v) void ExprPos::eval(EvalState & state, Env & env, Value & v)
{ {
state.mkPos(v, &pos); state.mkPos(v, ptr(&pos));
} }

View file

@ -308,7 +308,7 @@ public:
void mkList(Value & v, size_t length); void mkList(Value & v, size_t length);
void mkAttrs(Value & v, size_t capacity); void mkAttrs(Value & v, size_t capacity);
void mkThunk_(Value & v, Expr * expr); void mkThunk_(Value & v, Expr * expr);
void mkPos(Value & v, Pos * pos); void mkPos(Value & v, ptr<Pos> pos);
void concatLists(Value & v, size_t nrLists, Value * * lists, const Pos & pos); void concatLists(Value & v, size_t nrLists, Value * * lists, const Pos & pos);

View file

@ -2109,7 +2109,7 @@ void prim_getAttr(EvalState & state, const Pos & pos, Value * * args, Value & v)
pos pos
); );
// !!! add to stack trace? // !!! add to stack trace?
if (state.countCalls && i->pos) state.attrSelects[*i->pos]++; if (state.countCalls && *i->pos != noPos) state.attrSelects[*i->pos]++;
state.forceValue(*i->value, pos); state.forceValue(*i->value, pos);
v = *i->value; v = *i->value;
} }
@ -2369,7 +2369,7 @@ static void prim_functionArgs(EvalState & state, const Pos & pos, Value * * args
for (auto & i : args[0]->lambda.fun->formals->formals) { for (auto & i : args[0]->lambda.fun->formals->formals) {
// !!! should optimise booleans (allocate only once) // !!! should optimise booleans (allocate only once)
Value * value = state.allocValue(); Value * value = state.allocValue();
v.attrs->push_back(Attr(i.name, value, &i.pos)); v.attrs->push_back(Attr(i.name, value, ptr(&i.pos)));
mkBool(*value, i.def); mkBool(*value, i.def);
} }
v.attrs->sort(); v.attrs->sort();

View file

@ -42,7 +42,7 @@ static void showAttrs(EvalState & state, bool strict, bool location,
XMLAttrs xmlAttrs; XMLAttrs xmlAttrs;
xmlAttrs["name"] = i; xmlAttrs["name"] = i;
if (location && a.pos != &noPos) posToXML(xmlAttrs, *a.pos); if (location && a.pos != ptr(&noPos)) posToXML(xmlAttrs, *a.pos);
XMLOpenElement _(doc, "attr", xmlAttrs); XMLOpenElement _(doc, "attr", xmlAttrs);
printValueAsXML(state, strict, location, printValueAsXML(state, strict, location,

View file

@ -99,4 +99,47 @@ make_ref(Args&&... args)
return ref<T>(p); return ref<T>(p);
} }
/* A non-nullable pointer.
This is similar to a C++ "& reference", but mutable.
This is similar to ref<T> but backed by a regular pointer instead of a smart pointer.
*/
template<typename T>
class ptr {
private:
T * p;
public:
ptr<T>(const ptr<T> & r)
: p(r.p)
{ }
explicit ptr<T>(T * p)
: p(p)
{
if (!p)
throw std::invalid_argument("null pointer cast to ptr");
}
T* operator ->() const
{
return &*p;
}
T& operator *() const
{
return *p;
}
bool operator == (const ptr<T> & other) const
{
return p == other.p;
}
bool operator != (const ptr<T> & other) const
{
return p != other.p;
}
};
} }

View file

@ -131,9 +131,9 @@ bool createUserEnv(EvalState & state, DrvInfos & elems,
state.forceValue(topLevel); state.forceValue(topLevel);
PathSet context; PathSet context;
Attr & aDrvPath(*topLevel.attrs->find(state.sDrvPath)); Attr & aDrvPath(*topLevel.attrs->find(state.sDrvPath));
auto topLevelDrv = state.store->parseStorePath(state.coerceToPath(aDrvPath.pos ? *(aDrvPath.pos) : noPos, *(aDrvPath.value), context)); auto topLevelDrv = state.store->parseStorePath(state.coerceToPath(*aDrvPath.pos, *(aDrvPath.value), context));
Attr & aOutPath(*topLevel.attrs->find(state.sOutPath)); Attr & aOutPath(*topLevel.attrs->find(state.sOutPath));
Path topLevelOut = state.coerceToPath(aOutPath.pos ? *(aOutPath.pos) : noPos, *(aOutPath.value), context); Path topLevelOut = state.coerceToPath(*aOutPath.pos, *(aOutPath.value), context);
/* Realise the resulting store expression. */ /* Realise the resulting store expression. */
debug("building user environment"); debug("building user environment");