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Use boost small vectors instead of VLAs in the primops

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VLAs are a dangerous feature, and their usage triggers an undefined
behavior since theire size can be zero in some cases.
So replace them with `boost::small_vector`s which fit the same goal but
are safer.

It's also incidentally consistently 1% faster on the benchmarks.
This commit is contained in:
Théophane Hufschmitt 2022-11-18 11:13:32 +01:00 committed by Robert Hensing
parent e34c424279
commit 5196613e82
1 changed files with 5 additions and 7 deletions
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12
src/libexpr/primops.cc
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@ -29,7 +29,6 @@
#include <cmath> #include <cmath>
namespace nix { namespace nix {
@ -2729,8 +2728,8 @@ static void prim_catAttrs(EvalState & state, const PosIdx pos, Value * * args, V
auto attrName = state.symbols.create(state.forceStringNoCtx(*args[0], pos, "while evaluating the first argument passed to builtins.catAttrs")); auto attrName = state.symbols.create(state.forceStringNoCtx(*args[0], pos, "while evaluating the first argument passed to builtins.catAttrs"));
state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.catAttrs"); state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.catAttrs");
Value * res[args[1]->listSize()]; boost::container::small_vector<Value *, 256> res(args[1]->listSize());
unsigned int found = 0; size_t found = 0;
for (auto v2 : args[1]->listItems()) { for (auto v2 : args[1]->listItems()) {
state.forceAttrs(*v2, pos, "while evaluating an element in the list passed as second argument to builtins.catAttrs"); state.forceAttrs(*v2, pos, "while evaluating an element in the list passed as second argument to builtins.catAttrs");
@ -3064,9 +3063,8 @@ static void prim_filter(EvalState & state, const PosIdx pos, Value * * args, Val
state.forceFunction(*args[0], pos, "while evaluating the first argument passed to builtins.filter"); state.forceFunction(*args[0], pos, "while evaluating the first argument passed to builtins.filter");
// FIXME: putting this on the stack is risky. boost::container::small_vector<Value *, 256> vs(args[1]->listSize());
Value * vs[args[1]->listSize()]; size_t k = 0;
unsigned int k = 0;
bool same = true; bool same = true;
for (unsigned int n = 0; n < args[1]->listSize(); ++n) { for (unsigned int n = 0; n < args[1]->listSize(); ++n) {
@ -3450,7 +3448,7 @@ static void prim_concatMap(EvalState & state, const PosIdx pos, Value * * args,
state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.concatMap"); state.forceList(*args[1], pos, "while evaluating the second argument passed to builtins.concatMap");
auto nrLists = args[1]->listSize(); auto nrLists = args[1]->listSize();
Value lists[nrLists]; boost::container::small_vector<Value, 64> lists(nrLists);
size_t len = 0; size_t len = 0;
for (unsigned int n = 0; n < nrLists; ++n) { for (unsigned int n = 0; n < nrLists; ++n) {