Merge pull request #7348 from thufschmitt/dont-use-vlas
Remove the usage of VLAs in the code
(cherry picked from commit ac4431e9d016e62fb5dc9ae36833bd0c6cdadeec)
Change-Id: Ifbf5fbfc2e27122362a2aaea4b62c7cf3ca46b1a
This commit is contained in:
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30f3298e9d
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@ -1,6 +1,7 @@
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#include "eval.hh"
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#include "eval-settings.hh"
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#include "hash.hh"
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#include "primops.hh"
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#include "types.hh"
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#include "util.hh"
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#include "store-api.hh"
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@ -38,6 +39,7 @@
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#include <boost/coroutine2/coroutine.hpp>
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#include <boost/coroutine2/protected_fixedsize_stack.hpp>
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#include <boost/context/stack_context.hpp>
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#include <boost/container/small_vector.hpp>
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#endif
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@ -703,6 +705,23 @@ void EvalState::addConstant(const std::string & name, Value * v, Constant info)
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}
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void PrimOp::check()
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{
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if (arity > maxPrimOpArity) {
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throw Error("primop arity must not exceed %1%", maxPrimOpArity);
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}
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}
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void Value::mkPrimOp(PrimOp * p)
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{
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p->check();
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clearValue();
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internalType = tPrimOp;
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primOp = p;
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}
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Value * EvalState::addPrimOp(PrimOp && primOp)
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{
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/* Hack to make constants lazy: turn them into a application of
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@ -1683,7 +1702,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
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/* We have all the arguments, so call the primop with
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the previous and new arguments. */
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Value * vArgs[arity];
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Value * vArgs[maxPrimOpArity];
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auto n = argsDone;
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for (Value * arg = &vCur; arg->isPrimOpApp(); arg = arg->primOpApp.left)
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vArgs[--n] = arg->primOpApp.right;
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@ -1740,11 +1759,17 @@ void ExprCall::eval(EvalState & state, Env & env, Value & v)
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Value vFun;
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fun->eval(state, env, vFun);
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Value * vArgs[args.size()];
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// Empirical arity of Nixpkgs lambdas by regex e.g. ([a-zA-Z]+:(\s|(/\*.*\/)|(#.*\n))*){5}
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// 2: over 4000
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// 3: about 300
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// 4: about 60
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// 5: under 10
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// This excluded attrset lambdas (`{...}:`). Contributions of mixed lambdas appears insignificant at ~150 total.
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boost::container::small_vector<Value *, 4> vArgs(args.size());
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for (size_t i = 0; i < args.size(); ++i)
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vArgs[i] = args[i]->maybeThunk(state, env);
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state.callFunction(vFun, args.size(), vArgs, v, pos);
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state.callFunction(vFun, args.size(), vArgs.data(), v, pos);
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}
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@ -1983,8 +2008,8 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
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return result;
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};
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Value values[es->size()];
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Value * vTmpP = values;
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boost::container::small_vector<Value, conservativeStackReservation> values(es->size());
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Value * vTmpP = values.data();
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for (auto & [i_pos, i] : *es) {
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Value & vTmp = *vTmpP++;
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@ -18,6 +18,12 @@
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namespace nix {
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/**
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* We put a limit on primop arity because it lets us use a fixed size array on
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* the stack. 8 is already an impractical number of arguments. Use an attrset
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* argument for such overly complicated functions.
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*/
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constexpr size_t maxPrimOpArity = 8;
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class Store;
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class EvalState;
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@ -69,6 +75,12 @@ struct PrimOp
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* Optional experimental for this to be gated on.
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*/
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std::optional<ExperimentalFeature> experimentalFeature;
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/**
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* Validity check to be performed by functions that introduce primops,
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* such as RegisterPrimOp() and Value::mkPrimOp().
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*/
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void check();
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};
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/**
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@ -28,7 +28,6 @@
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#include <cmath>
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namespace nix {
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@ -2547,6 +2546,7 @@ static void prim_removeAttrs(EvalState & state, const PosIdx pos, Value * * args
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/* Get the attribute names to be removed.
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We keep them as Attrs instead of Symbols so std::set_difference
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can be used to remove them from attrs[0]. */
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// 64: large enough to fit the attributes of a derivation
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boost::container::small_vector<Attr, 64> names;
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names.reserve(args[1]->listSize());
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for (auto elem : args[1]->listItems()) {
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@ -2726,8 +2726,8 @@ static void prim_catAttrs(EvalState & state, const PosIdx pos, Value * * args, V
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auto attrName = state.symbols.create(state.forceStringNoCtx(*args[0], pos, "while evaluating the first argument passed to builtins.catAttrs"));
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state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.catAttrs");
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Value * res[args[1]->listSize()];
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unsigned int found = 0;
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boost::container::small_vector<Value *, nonRecursiveStackReservation> res(args[1]->listSize());
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size_t found = 0;
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for (auto v2 : args[1]->listItems()) {
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state.forceAttrs(*v2, pos, "while evaluating an element in the list passed as second argument to builtins.catAttrs");
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@ -3061,9 +3061,8 @@ static void prim_filter(EvalState & state, const PosIdx pos, Value * * args, Val
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state.forceFunction(*args[0], pos, "while evaluating the first argument passed to builtins.filter");
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// FIXME: putting this on the stack is risky.
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Value * vs[args[1]->listSize()];
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unsigned int k = 0;
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boost::container::small_vector<Value *, nonRecursiveStackReservation> vs(args[1]->listSize());
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size_t k = 0;
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bool same = true;
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for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
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@ -3188,10 +3187,14 @@ static void anyOrAll(bool any, EvalState & state, const PosIdx pos, Value * * ar
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state.forceFunction(*args[0], pos, std::string("while evaluating the first argument passed to builtins.") + (any ? "any" : "all"));
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state.forceList(*args[1], pos, std::string("while evaluating the second argument passed to builtins.") + (any ? "any" : "all"));
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std::string_view errorCtx = any
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? "while evaluating the return value of the function passed to builtins.any"
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: "while evaluating the return value of the function passed to builtins.all";
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Value vTmp;
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for (auto elem : args[1]->listItems()) {
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state.callFunction(*args[0], *elem, vTmp, pos);
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bool res = state.forceBool(vTmp, pos, std::string("while evaluating the return value of the function passed to builtins.") + (any ? "any" : "all"));
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bool res = state.forceBool(vTmp, pos, errorCtx);
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if (res == any) {
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v.mkBool(any);
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return;
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@ -3447,7 +3450,7 @@ static void prim_concatMap(EvalState & state, const PosIdx pos, Value * * args,
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state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.concatMap");
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auto nrLists = args[1]->listSize();
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Value lists[nrLists];
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boost::container::small_vector<Value, conservativeStackReservation> lists(nrLists);
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size_t len = 0;
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for (unsigned int n = 0; n < nrLists; ++n) {
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@ -8,6 +8,22 @@
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namespace nix {
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/**
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* For functions where we do not expect deep recursion, we can use a sizable
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* part of the stack a free allocation space.
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*
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* Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
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*/
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constexpr size_t nonRecursiveStackReservation = 128;
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/**
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* Functions that maybe applied to self-similar inputs, such as concatMap on a
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* tree, should reserve a smaller part of the stack for allocation.
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*
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* Note: this is expected to be multiplied by sizeof(Value), or about 24 bytes.
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*/
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constexpr size_t conservativeStackReservation = 16;
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struct RegisterPrimOp
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{
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typedef std::vector<PrimOp> PrimOps;
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@ -349,13 +349,7 @@ public:
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// Value will be overridden anyways
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}
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inline void mkPrimOp(PrimOp * p)
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{
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clearValue();
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internalType = tPrimOp;
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primOp = p;
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}
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void mkPrimOp(PrimOp * p);
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inline void mkPrimOpApp(Value * l, Value * r)
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{
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@ -152,11 +152,10 @@ StorePath writeDerivation(Store & store,
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/* Read string `s' from stream `str'. */
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static void expect(std::istream & str, std::string_view s)
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{
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char s2[s.size()];
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str.read(s2, s.size());
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std::string_view s2View { s2, s.size() };
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if (s2View != s)
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throw FormatError("expected string '%s', got '%s'", s, s2View);
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for (auto & c : s) {
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if (str.get() != c)
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throw FormatError("expected string '%1%'", s);
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}
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}
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@ -323,9 +323,7 @@ typedef std::unordered_map<Path, std::unordered_set<std::string>> UncheckedRoots
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static void readProcLink(const std::string & file, UncheckedRoots & roots)
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{
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/* 64 is the starting buffer size gnu readlink uses... */
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auto bufsiz = ssize_t{64};
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try_again:
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constexpr auto bufsiz = PATH_MAX;
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char buf[bufsiz];
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auto res = readlink(file.c_str(), buf, bufsiz);
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if (res == -1) {
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throw SysError("reading symlink");
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}
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if (res == bufsiz) {
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if (SSIZE_MAX / 2 < bufsiz)
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throw Error("stupidly long symlink");
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bufsiz *= 2;
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goto try_again;
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throw Error("overly long symlink starting with '%1%'", std::string_view(buf, bufsiz));
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}
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if (res > 0 && buf[0] == '/')
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roots[std::string(static_cast<char *>(buf), res)]
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TEST_F(ValuePrintingTests, vPrimOp)
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{
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Value vPrimOp;
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vPrimOp.mkPrimOp(nullptr);
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PrimOp primOp{};
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vPrimOp.mkPrimOp(&primOp);
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test(vPrimOp, "<PRIMOP>");
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}
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