No global eval settings in libnixexpr

Progress on #5638

There is still a global eval settings, but it pushed down into
`libnixcmd`, which is a lot less bad a place for this sort of thing.

.editorconfig

@@ -4,20 +4,20 @@
 # Top-most EditorConfig file
 root = true
 
-# Unix-style newlines with a newline ending every file, utf-8 charset
+# Unix-style newlines with a newline ending every file, UTF-8 charset
 [*]
 end_of_line = lf
 insert_final_newline = true
 trim_trailing_whitespace = true
 charset = utf-8
 
-# Match nix files, set indent to spaces with width of two
+# Match Nix files, set indent to spaces with width of two
 [*.nix]
 indent_style = space
 indent_size = 2
 
-# Match c++/shell/perl, set indent to spaces with width of four
-[*.{hpp,cc,hh,sh,pl,xs}]
+# Match C++/C/shell/Perl, set indent to spaces with width of four
+[*.{hpp,cc,hh,c,h,sh,pl,xs}]
 indent_style = space
 indent_size = 4
 

src/libcmd/command.cc

@@ -126,13 +126,11 @@ ref<EvalState> EvalCommand::getEvalState()
 {
     if (!evalState) {
         evalState =
+            std::allocate_shared<EvalState>(
             #if HAVE_BOEHMGC
-            std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
-                lookupPath, getEvalStore(), getStore())
-            #else
-            std::make_shared<EvalState>(
-                lookupPath, getEvalStore(), getStore())
+                traceable_allocator<EvalState>(),
             #endif
+                lookupPath, getEvalStore(), globalEvalSettings, getStore())
             ;
 
         evalState->repair = repair;

src/libcmd/common-eval-args.cc

@@ -13,6 +13,12 @@
 
 namespace nix {
 
+EvalSettings globalEvalSettings {
+    settings.readOnlyMode
+};
+
+static GlobalConfig::Register rEvalSettings(&globalEvalSettings);
+
 MixEvalArgs::MixEvalArgs()
 {
     addFlag({
@@ -134,7 +140,7 @@ MixEvalArgs::MixEvalArgs()
         .description = "Allow access to mutable paths and repositories.",
         .category = category,
         .handler = {[&]() {
-            evalSettings.pureEval = false;
+            globalEvalSettings.pureEval = false;
         }},
     });
 

src/libcmd/common-eval-args.hh

@@ -12,9 +12,15 @@ namespace nix {
 
 class Store;
 class EvalState;
+struct EvalSettings;
 class Bindings;
 struct SourcePath;
 
+/**
+ * @todo Get rid of global setttings variables
+ */
+extern EvalSettings globalEvalSettings;
+
 struct MixEvalArgs : virtual Args, virtual MixRepair
 {
     static constexpr auto category = "Common evaluation options";

src/libcmd/installables.cc

@@ -258,7 +258,7 @@ void SourceExprCommand::completeInstallable(AddCompletions & completions, std::s
         if (file) {
             completions.setType(AddCompletions::Type::Attrs);
 
-            evalSettings.pureEval = false;
+            globalEvalSettings.pureEval = false;
             auto state = getEvalState();
             auto e =
                 state->parseExprFromFile(
@@ -442,7 +442,7 @@ ref<eval_cache::EvalCache> openEvalCache(
     EvalState & state,
     std::shared_ptr<flake::LockedFlake> lockedFlake)
 {
-    auto fingerprint = evalSettings.useEvalCache && evalSettings.pureEval
+    auto fingerprint = globalEvalSettings.useEvalCache && globalEvalSettings.pureEval
         ? lockedFlake->getFingerprint(state.store)
         : std::nullopt;
     auto rootLoader = [&state, lockedFlake]()
@@ -484,7 +484,7 @@ Installables SourceExprCommand::parseInstallables(
             throw UsageError("'--file' and '--expr' are exclusive");
 
         // FIXME: backward compatibility hack
-        if (file) evalSettings.pureEval = false;
+        if (file) globalEvalSettings.pureEval = false;
 
         auto state = getEvalState();
         auto vFile = state->allocValue();

src/libcmd/repl.cc

@@ -690,7 +690,7 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
         throw Error("cannot use ':load-flake' without a path specified. (Use '.' for the current working directory.)");
 
     auto flakeRef = parseFlakeRef(flakeRefS, absPath("."), true);
-    if (evalSettings.pureEval && !flakeRef.input.isLocked())
+    if (globalEvalSettings.pureEval && !flakeRef.input.isLocked())
         throw Error("cannot use ':load-flake' on locked flake reference '%s' (use --impure to override)", flakeRefS);
 
     Value v;
@@ -699,8 +699,8 @@ void NixRepl::loadFlake(const std::string & flakeRefS)
         flake::lockFlake(*state, flakeRef,
             flake::LockFlags {
                 .updateLockFile = false,
-                .useRegistries = !evalSettings.pureEval,
-                .allowUnlocked = !evalSettings.pureEval,
+                .useRegistries = !globalEvalSettings.pureEval,
+                .allowUnlocked = !globalEvalSettings.pureEval,
             }),
         v);
     addAttrsToScope(v);

src/libexpr-c/nix_api_expr.cc

@@ -7,6 +7,7 @@
 #include "eval.hh"
 #include "globals.hh"
 #include "util.hh"
+#include "eval-settings.hh"
 
 #include "nix_api_expr.h"
 #include "nix_api_expr_internal.h"
@@ -106,7 +107,20 @@ EvalState * nix_state_create(nix_c_context * context, const char ** lookupPath_c
             for (size_t i = 0; lookupPath_c[i] != nullptr; i++)
                 lookupPath.push_back(lookupPath_c[i]);
 
-        return new EvalState{nix::EvalState(nix::LookupPath::parse(lookupPath), store->ptr)};
+        void * p = ::operator new(
+            sizeof(EvalState),
+            static_cast<std::align_val_t>(alignof(EvalState)));
+        auto * p2 = static_cast<EvalState *>(p);
+        return new (p) EvalState {
+            .readOnlyMode = false,
+            .settings = nix::EvalSettings{
+                p2->readOnlyMode,
+            },
+            .state = nix::EvalState(
+                nix::LookupPath::parse(lookupPath),
+                store->ptr,
+                p2->settings),
+        };
     }
     NIXC_CATCH_ERRS_NULL
 }

src/libexpr-c/nix_api_expr_internal.h

@@ -2,11 +2,14 @@
 #define NIX_API_EXPR_INTERNAL_H
 
 #include "eval.hh"
+#include "eval-settings.hh"
 #include "attr-set.hh"
 #include "nix_api_value.h"
 
 struct EvalState
 {
+    bool readOnlyMode;
+    nix::EvalSettings settings;
     nix::EvalState state;
 };
 

src/libexpr/eval-settings.cc

@@ -44,7 +44,8 @@ static Strings parseNixPath(const std::string & s)
     return res;
 }
 
-EvalSettings::EvalSettings()
+EvalSettings::EvalSettings(bool & readOnlyMode)
+    : readOnlyMode{readOnlyMode}
 {
     auto var = getEnv("NIX_PATH");
     if (var) nixPath = parseNixPath(*var);
@@ -54,7 +55,7 @@ EvalSettings::EvalSettings()
         builtinsAbortOnWarn = true;
 }
 
-Strings EvalSettings::getDefaultNixPath()
+Strings EvalSettings::getDefaultNixPath() const
 {
     Strings res;
     auto add = [&](const Path & p, const std::string & s = std::string()) {
@@ -67,7 +68,7 @@ Strings EvalSettings::getDefaultNixPath()
         }
     };
 
-    if (!evalSettings.restrictEval && !evalSettings.pureEval) {
+    if (!restrictEval && !pureEval) {
         add(getNixDefExpr() + "/channels");
         add(rootChannelsDir() + "/nixpkgs", "nixpkgs");
         add(rootChannelsDir());
@@ -93,16 +94,12 @@ std::string EvalSettings::resolvePseudoUrl(std::string_view url)
         return std::string(url);
 }
 
-const std::string & EvalSettings::getCurrentSystem()
+const std::string & EvalSettings::getCurrentSystem() const
 {
     const auto & evalSystem = currentSystem.get();
     return evalSystem != "" ? evalSystem : settings.thisSystem.get();
 }
 
-EvalSettings evalSettings;
-
-static GlobalConfig::Register rEvalSettings(&evalSettings);
-
 Path getNixDefExpr()
 {
     return settings.useXDGBaseDirectories

src/libexpr/eval-settings.hh

@@ -7,9 +7,11 @@ namespace nix {
 
 struct EvalSettings : Config
 {
-    EvalSettings();
+    EvalSettings(bool & readOnlyMode);
 
-    static Strings getDefaultNixPath();
+    bool & readOnlyMode;
+
+    Strings getDefaultNixPath() const;
 
     static bool isPseudoUrl(std::string_view s);
 
@@ -74,7 +76,7 @@ struct EvalSettings : Config
      * Implements the `eval-system` vs `system` defaulting logic
      * described for `eval-system`.
      */
-    const std::string & getCurrentSystem();
+    const std::string & getCurrentSystem() const;
 
     Setting<bool> restrictEval{
         this, false, "restrict-eval",
@@ -193,8 +195,6 @@ struct EvalSettings : Config
         )"};
 };
 
-extern EvalSettings evalSettings;
-
 /**
  * Conventionally part of the default nix path in impure mode.
  */

src/libexpr/eval.cc

@@ -9,7 +9,6 @@
 #include "store-api.hh"
 #include "derivations.hh"
 #include "downstream-placeholder.hh"
-#include "globals.hh"
 #include "eval-inline.hh"
 #include "filetransfer.hh"
 #include "function-trace.hh"
@@ -219,8 +218,10 @@ static constexpr size_t BASE_ENV_SIZE = 128;
 EvalState::EvalState(
     const LookupPath & _lookupPath,
     ref<Store> store,
+    const EvalSettings & settings,
     std::shared_ptr<Store> buildStore)
-    : sWith(symbols.create("<with>"))
+    : settings{settings}
+    , sWith(symbols.create("<with>"))
     , sOutPath(symbols.create("outPath"))
     , sDrvPath(symbols.create("drvPath"))
     , sType(symbols.create("type"))
@@ -270,10 +271,10 @@ EvalState::EvalState(
     , repair(NoRepair)
     , emptyBindings(0)
     , rootFS(
-        evalSettings.restrictEval || evalSettings.pureEval
+        settings.restrictEval || settings.pureEval
         ? ref<SourceAccessor>(AllowListSourceAccessor::create(getFSSourceAccessor(), {},
-            [](const CanonPath & path) -> RestrictedPathError {
-                auto modeInformation = evalSettings.pureEval
+            [&settings](const CanonPath & path) -> RestrictedPathError {
+                auto modeInformation = settings.pureEval
                     ? "in pure evaluation mode (use '--impure' to override)"
                     : "in restricted mode";
                 throw RestrictedPathError("access to absolute path '%1%' is forbidden %2%", path, modeInformation);
@@ -324,10 +325,10 @@ EvalState::EvalState(
     vStringUnknown.mkString("unknown");
 
     /* Initialise the Nix expression search path. */
-    if (!evalSettings.pureEval) {
+    if (!settings.pureEval) {
         for (auto & i : _lookupPath.elements)
             lookupPath.elements.emplace_back(LookupPath::Elem {i});
-        for (auto & i : evalSettings.nixPath.get())
+        for (auto & i : settings.nixPath.get())
             lookupPath.elements.emplace_back(LookupPath::Elem::parse(i));
     }
 
@@ -405,9 +406,9 @@ bool isAllowedURI(std::string_view uri, const Strings & allowedUris)
 
 void EvalState::checkURI(const std::string & uri)
 {
-    if (!evalSettings.restrictEval) return;
+    if (!settings.restrictEval) return;
 
-    if (isAllowedURI(uri, evalSettings.allowedUris.get())) return;
+    if (isAllowedURI(uri, settings.allowedUris.get())) return;
 
     /* If the URI is a path, then check it against allowedPaths as
        well. */
@@ -452,7 +453,7 @@ void EvalState::addConstant(const std::string & name, Value * v, Constant info)
 
     constantInfos.push_back({name2, info});
 
-    if (!(evalSettings.pureEval && info.impureOnly)) {
+    if (!(settings.pureEval && info.impureOnly)) {
         /* Check the type, if possible.
 
            We might know the type of a thunk in advance, so be allowed
@@ -1407,11 +1408,11 @@ class CallDepth {
 
 void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value & vRes, const PosIdx pos)
 {
-    if (callDepth > evalSettings.maxCallDepth)
+    if (callDepth > settings.maxCallDepth)
         error<EvalError>("stack overflow; max-call-depth exceeded").atPos(pos).debugThrow();
     CallDepth _level(callDepth);
 
-    auto trace = evalSettings.traceFunctionCalls
+    auto trace = settings.traceFunctionCalls
         ? std::make_unique<FunctionCallTrace>(positions[pos])
         : nullptr;
 
@@ -2739,7 +2740,7 @@ SourcePath EvalState::findFile(const LookupPath & lookupPath, const std::string_
         return {corepkgsFS, CanonPath(path.substr(3))};
 
     error<ThrownError>(
-        evalSettings.pureEval
+        settings.pureEval
             ? "cannot look up '<%s>' in pure evaluation mode (use '--impure' to override)"
             : "file '%s' was not found in the Nix search path (add it using $NIX_PATH or -I)",
         path
@@ -2819,7 +2820,7 @@ Expr * EvalState::parse(
     const SourcePath & basePath,
     std::shared_ptr<StaticEnv> & staticEnv)
 {
-    auto result = parseExprFromBuf(text, length, origin, basePath, symbols, positions, rootFS, exprSymbols);
+    auto result = parseExprFromBuf(text, length, origin, basePath, symbols, settings, positions, rootFS, exprSymbols);
 
     result->bindVars(*this, staticEnv);
 

src/libexpr/eval.hh

@@ -30,6 +30,7 @@ namespace nix {
 constexpr size_t maxPrimOpArity = 8;
 
 class Store;
+struct EvalSettings;
 class EvalState;
 class StorePath;
 struct SingleDerivedPath;
@@ -39,7 +40,6 @@ namespace eval_cache {
     class EvalCache;
 }
 
-
 /**
  * Function that implements a primop.
  */
@@ -162,6 +162,7 @@ struct DebugTrace {
 class EvalState : public std::enable_shared_from_this<EvalState>
 {
 public:
+    const EvalSettings & settings;
     SymbolTable symbols;
     PosTable positions;
 
@@ -349,6 +350,7 @@ public:
     EvalState(
         const LookupPath & _lookupPath,
         ref<Store> store,
+        const EvalSettings & settings,
         std::shared_ptr<Store> buildStore = nullptr);
     ~EvalState();
 

src/libexpr/flake/config.cc

@@ -1,5 +1,4 @@
 #include "users.hh"
-#include "globals.hh"
 #include "fetch-settings.hh"
 #include "flake.hh"