lix/src/libexpr/eval.hh
pennae a385e51a08 rename SymbolIdx -> Symbol, Symbol -> SymbolStr
after #6218 `Symbol` no longer confers a uniqueness invariant on the
string it wraps, it is now possible to create multiple symbols that
compare equal but whose string contents have different addresses. this
guarantee is now only provided by `SymbolIdx`, leaving `Symbol` only as
a string wrapper that knows about the intricacies of how symbols need to
be formatted for output.

this change renames `SymbolIdx` to `Symbol` to restore the previous
semantics of `Symbol` to that name. we also keep the wrapper type and
rename it to `SymbolStr` instead of returning plain strings from lookups
into the symbol table because symbols are formatted for output in many
places. theoretically we do not need `SymbolStr`, only a function that
formats a string for output as a symbol, but having to wrap every symbol
that appears in a message into eg `formatSymbol()` is error-prone and
inconvient.
2022-04-25 15:37:01 +02:00

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#pragma once
#include "attr-set.hh"
#include "types.hh"
#include "value.hh"
#include "nixexpr.hh"
#include "symbol-table.hh"
#include "config.hh"
#include "experimental-features.hh"
#include <map>
#include <optional>
#include <unordered_map>
#include <mutex>
namespace nix {
class Store;
class EvalState;
class StorePath;
enum RepairFlag : bool;
typedef void (* PrimOpFun) (EvalState & state, const PosIdx pos, Value * * args, Value & v);
struct PrimOp
{
PrimOpFun fun;
size_t arity;
std::string name;
std::vector<std::string> args;
const char * doc = nullptr;
};
struct Env
{
Env * up;
unsigned short prevWith:14; // nr of levels up to next `with' environment
enum { Plain = 0, HasWithExpr, HasWithAttrs } type:2;
Value * values[0];
};
void copyContext(const Value & v, PathSet & context);
/* Cache for calls to addToStore(); maps source paths to the store
paths. */
typedef std::map<Path, StorePath> SrcToStore;
std::ostream & printValue(const EvalState & state, std::ostream & str, const Value & v);
std::string printValue(const EvalState & state, const Value & v);
typedef std::pair<std::string, std::string> SearchPathElem;
typedef std::list<SearchPathElem> SearchPath;
/* Initialise the Boehm GC, if applicable. */
void initGC();
struct RegexCache;
std::shared_ptr<RegexCache> makeRegexCache();
class EvalState
{
public:
SymbolTable symbols;
PosTable positions;
static inline std::string derivationNixPath = "//builtin/derivation.nix";
const Symbol sWith, sOutPath, sDrvPath, sType, sMeta, sName, sValue,
sSystem, sOverrides, sOutputs, sOutputName, sIgnoreNulls,
sFile, sLine, sColumn, sFunctor, sToString,
sRight, sWrong, sStructuredAttrs, sBuilder, sArgs,
sContentAddressed, sImpure,
sOutputHash, sOutputHashAlgo, sOutputHashMode,
sRecurseForDerivations,
sDescription, sSelf, sEpsilon, sStartSet, sOperator, sKey, sPath,
sPrefix;
Symbol sDerivationNix;
/* If set, force copying files to the Nix store even if they
already exist there. */
RepairFlag repair;
/* The allowed filesystem paths in restricted or pure evaluation
mode. */
std::optional<PathSet> allowedPaths;
Bindings emptyBindings;
/* Store used to materialise .drv files. */
const ref<Store> store;
/* Store used to build stuff. */
const ref<Store> buildStore;
RootValue vCallFlake = nullptr;
RootValue vImportedDrvToDerivation = nullptr;
private:
SrcToStore srcToStore;
/* A cache from path names to parse trees. */
#if HAVE_BOEHMGC
typedef std::map<Path, Expr *, std::less<Path>, traceable_allocator<std::pair<const Path, Expr *> > > FileParseCache;
#else
typedef std::map<Path, Expr *> FileParseCache;
#endif
FileParseCache fileParseCache;
/* A cache from path names to values. */
#if HAVE_BOEHMGC
typedef std::map<Path, Value, std::less<Path>, traceable_allocator<std::pair<const Path, Value> > > FileEvalCache;
#else
typedef std::map<Path, Value> FileEvalCache;
#endif
FileEvalCache fileEvalCache;
SearchPath searchPath;
std::map<std::string, std::pair<bool, std::string>> searchPathResolved;
/* Cache used by checkSourcePath(). */
std::unordered_map<Path, Path> resolvedPaths;
/* Cache used by prim_match(). */
std::shared_ptr<RegexCache> regexCache;
#if HAVE_BOEHMGC
/* Allocation cache for GC'd Value objects. */
std::shared_ptr<void *> valueAllocCache;
/* Allocation cache for size-1 Env objects. */
std::shared_ptr<void *> env1AllocCache;
#endif
public:
EvalState(
const Strings & _searchPath,
ref<Store> store,
std::shared_ptr<Store> buildStore = nullptr);
~EvalState();
void addToSearchPath(const std::string & s);
SearchPath getSearchPath() { return searchPath; }
/* Allow access to a path. */
void allowPath(const Path & path);
/* Allow access to a store path. Note that this gets remapped to
the real store path if `store` is a chroot store. */
void allowPath(const StorePath & storePath);
/* Allow access to a store path and return it as a string. */
void allowAndSetStorePathString(const StorePath & storePath, Value & v);
/* Check whether access to a path is allowed and throw an error if
not. Otherwise return the canonicalised path. */
Path checkSourcePath(const Path & path);
void checkURI(const std::string & uri);
/* When using a diverted store and 'path' is in the Nix store, map
'path' to the diverted location (e.g. /nix/store/foo is mapped
to /home/alice/my-nix/nix/store/foo). However, this is only
done if the context is not empty, since otherwise we're
probably trying to read from the actual /nix/store. This is
intended to distinguish between import-from-derivation and
sources stored in the actual /nix/store. */
Path toRealPath(const Path & path, const PathSet & context);
/* Parse a Nix expression from the specified file. */
Expr * parseExprFromFile(const Path & path);
Expr * parseExprFromFile(const Path & path, StaticEnv & staticEnv);
/* Parse a Nix expression from the specified string. */
Expr * parseExprFromString(std::string s, const Path & basePath, StaticEnv & staticEnv);
Expr * parseExprFromString(std::string s, const Path & basePath);
Expr * parseStdin();
/* Evaluate an expression read from the given file to normal
form. Optionally enforce that the top-level expression is
trivial (i.e. doesn't require arbitrary computation). */
void evalFile(const Path & path, Value & v, bool mustBeTrivial = false);
/* Like `cacheFile`, but with an already parsed expression. */
void cacheFile(
const Path & path,
const Path & resolvedPath,
Expr * e,
Value & v,
bool mustBeTrivial = false);
void resetFileCache();
/* Look up a file in the search path. */
Path findFile(const std::string_view path);
Path findFile(SearchPath & searchPath, const std::string_view path, const PosIdx pos = noPos);
/* If the specified search path element is a URI, download it. */
std::pair<bool, std::string> resolveSearchPathElem(const SearchPathElem & elem);
/* Evaluate an expression to normal form, storing the result in
value `v'. */
void eval(Expr * e, Value & v);
/* Evaluation the expression, then verify that it has the expected
type. */
inline bool evalBool(Env & env, Expr * e);
inline bool evalBool(Env & env, Expr * e, const PosIdx pos);
inline void evalAttrs(Env & env, Expr * e, Value & v);
/* If `v' is a thunk, enter it and overwrite `v' with the result
of the evaluation of the thunk. If `v' is a delayed function
application, call the function and overwrite `v' with the
result. Otherwise, this is a no-op. */
inline void forceValue(Value & v, const PosIdx pos);
template <typename Callable>
inline void forceValue(Value & v, Callable getPos);
/* Force a value, then recursively force list elements and
attributes. */
void forceValueDeep(Value & v);
/* Force `v', and then verify that it has the expected type. */
NixInt forceInt(Value & v, const PosIdx pos);
NixFloat forceFloat(Value & v, const PosIdx pos);
bool forceBool(Value & v, const PosIdx pos);
void forceAttrs(Value & v, const PosIdx pos);
template <typename Callable>
inline void forceAttrs(Value & v, Callable getPos);
inline void forceList(Value & v, const PosIdx pos);
void forceFunction(Value & v, const PosIdx pos); // either lambda or primop
std::string_view forceString(Value & v, const PosIdx pos = noPos);
std::string_view forceString(Value & v, PathSet & context, const PosIdx pos = noPos);
std::string_view forceStringNoCtx(Value & v, const PosIdx pos = noPos);
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s) const;
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s, const Value & v) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const char * s, const std::string & s2) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const std::string & s2) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s, const std::string & s2) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const char * s, const std::string & s2, const std::string & s3) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx pos, const char * s, const std::string & s2, const std::string & s3) const;
[[gnu::noinline, gnu::noreturn]]
void throwEvalError(const PosIdx p1, const char * s, const Symbol sym, const PosIdx p2) const;
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s) const;
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const char * s, const ExprLambda & fun, const Symbol s2) const;
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const PosIdx pos, const Suggestions & suggestions, const char * s,
const ExprLambda & fun, const Symbol s2) const;
[[gnu::noinline, gnu::noreturn]]
void throwTypeError(const char * s, const Value & v) const;
[[gnu::noinline, gnu::noreturn]]
void throwAssertionError(const PosIdx pos, const char * s, const std::string & s1) const;
[[gnu::noinline, gnu::noreturn]]
void throwUndefinedVarError(const PosIdx pos, const char * s, const std::string & s1) const;
[[gnu::noinline, gnu::noreturn]]
void throwMissingArgumentError(const PosIdx pos, const char * s, const std::string & s1) const;
[[gnu::noinline]]
void addErrorTrace(Error & e, const char * s, const std::string & s2) const;
[[gnu::noinline]]
void addErrorTrace(Error & e, const PosIdx pos, const char * s, const std::string & s2) const;
public:
/* Return true iff the value `v' denotes a derivation (i.e. a
set with attribute `type = "derivation"'). */
bool isDerivation(Value & v);
std::optional<std::string> tryAttrsToString(const PosIdx pos, Value & v,
PathSet & context, bool coerceMore = false, bool copyToStore = true);
/* String coercion. Converts strings, paths and derivations to a
string. If `coerceMore' is set, also converts nulls, integers,
booleans and lists to a string. If `copyToStore' is set,
referenced paths are copied to the Nix store as a side effect. */
BackedStringView coerceToString(const PosIdx pos, Value & v, PathSet & context,
bool coerceMore = false, bool copyToStore = true,
bool canonicalizePath = true);
std::string copyPathToStore(PathSet & context, const Path & path);
/* Path coercion. Converts strings, paths and derivations to a
path. The result is guaranteed to be a canonicalised, absolute
path. Nothing is copied to the store. */
Path coerceToPath(const PosIdx pos, Value & v, PathSet & context);
/* Like coerceToPath, but the result must be a store path. */
StorePath coerceToStorePath(const PosIdx pos, Value & v, PathSet & context);
public:
/* The base environment, containing the builtin functions and
values. */
Env & baseEnv;
/* The same, but used during parsing to resolve variables. */
StaticEnv staticBaseEnv; // !!! should be private
private:
unsigned int baseEnvDispl = 0;
void createBaseEnv();
Value * addConstant(const std::string & name, Value & v);
void addConstant(const std::string & name, Value * v);
Value * addPrimOp(const std::string & name,
size_t arity, PrimOpFun primOp);
Value * addPrimOp(PrimOp && primOp);
public:
Value & getBuiltin(const std::string & name);
struct Doc
{
Pos pos;
std::optional<std::string> name;
size_t arity;
std::vector<std::string> args;
const char * doc;
};
std::optional<Doc> getDoc(Value & v);
private:
inline Value * lookupVar(Env * env, const ExprVar & var, bool noEval);
friend struct ExprVar;
friend struct ExprAttrs;
friend struct ExprLet;
Expr * parse(char * text, size_t length, FileOrigin origin, const PathView path,
const PathView basePath, StaticEnv & staticEnv);
public:
/* Do a deep equality test between two values. That is, list
elements and attributes are compared recursively. */
bool eqValues(Value & v1, Value & v2);
bool isFunctor(Value & fun);
// FIXME: use std::span
void callFunction(Value & fun, size_t nrArgs, Value * * args, Value & vRes, const PosIdx pos);
void callFunction(Value & fun, Value & arg, Value & vRes, const PosIdx pos)
{
Value * args[] = {&arg};
callFunction(fun, 1, args, vRes, pos);
}
/* Automatically call a function for which each argument has a
default value or has a binding in the `args' map. */
void autoCallFunction(Bindings & args, Value & fun, Value & res);
/* Allocation primitives. */
inline Value * allocValue();
inline Env & allocEnv(size_t size);
Value * allocAttr(Value & vAttrs, const Symbol & name);
Value * allocAttr(Value & vAttrs, std::string_view name);
Bindings * allocBindings(size_t capacity);
BindingsBuilder buildBindings(size_t capacity)
{
return BindingsBuilder(*this, allocBindings(capacity));
}
void mkList(Value & v, size_t length);
void mkThunk_(Value & v, Expr * expr);
void mkPos(Value & v, PosIdx pos);
void concatLists(Value & v, size_t nrLists, Value * * lists, const PosIdx pos);
/* Print statistics. */
void printStats();
/* Realise the given context, and return a mapping from the placeholders
* used to construct the associated value to their final store path
*/
[[nodiscard]] StringMap realiseContext(const PathSet & context);
private:
unsigned long nrEnvs = 0;
unsigned long nrValuesInEnvs = 0;
unsigned long nrValues = 0;
unsigned long nrListElems = 0;
unsigned long nrLookups = 0;
unsigned long nrAttrsets = 0;
unsigned long nrAttrsInAttrsets = 0;
unsigned long nrAvoided = 0;
unsigned long nrOpUpdates = 0;
unsigned long nrOpUpdateValuesCopied = 0;
unsigned long nrListConcats = 0;
unsigned long nrPrimOpCalls = 0;
unsigned long nrFunctionCalls = 0;
bool countCalls;
typedef std::map<std::string, size_t> PrimOpCalls;
PrimOpCalls primOpCalls;
typedef std::map<ExprLambda *, size_t> FunctionCalls;
FunctionCalls functionCalls;
void incrFunctionCall(ExprLambda * fun);
typedef std::map<PosIdx, size_t> AttrSelects;
AttrSelects attrSelects;
friend struct ExprOpUpdate;
friend struct ExprOpConcatLists;
friend struct ExprVar;
friend struct ExprString;
friend struct ExprInt;
friend struct ExprFloat;
friend struct ExprPath;
friend struct ExprSelect;
friend void prim_getAttr(EvalState & state, const PosIdx pos, Value * * args, Value & v);
friend void prim_match(EvalState & state, const PosIdx pos, Value * * args, Value & v);
friend void prim_split(EvalState & state, const PosIdx pos, Value * * args, Value & v);
friend struct Value;
};
/* Return a string representing the type of the value `v'. */
std::string_view showType(ValueType type);
std::string showType(const Value & v);
/* Decode a context string !<name>!<path> into a pair <path,
name>. */
NixStringContextElem decodeContext(const Store & store, std::string_view s);
/* If `path' refers to a directory, then append "/default.nix". */
Path resolveExprPath(Path path);
struct InvalidPathError : EvalError
{
Path path;
InvalidPathError(const Path & path);
#ifdef EXCEPTION_NEEDS_THROW_SPEC
~InvalidPathError() throw () { };
#endif
};
struct EvalSettings : Config
{
EvalSettings();
static Strings getDefaultNixPath();
Setting<bool> enableNativeCode{this, false, "allow-unsafe-native-code-during-evaluation",
"Whether builtin functions that allow executing native code should be enabled."};
Setting<Strings> nixPath{
this, getDefaultNixPath(), "nix-path",
"List of directories to be searched for `<...>` file references."};
Setting<bool> restrictEval{
this, false, "restrict-eval",
R"(
If set to `true`, the Nix evaluator will not allow access to any
files outside of the Nix search path (as set via the `NIX_PATH`
environment variable or the `-I` option), or to URIs outside of
`allowed-uri`. The default is `false`.
)"};
Setting<bool> pureEval{this, false, "pure-eval",
"Whether to restrict file system and network access to files specified by cryptographic hash."};
Setting<bool> enableImportFromDerivation{
this, true, "allow-import-from-derivation",
R"(
By default, Nix allows you to `import` from a derivation, allowing
building at evaluation time. With this option set to false, Nix will
throw an error when evaluating an expression that uses this feature,
allowing users to ensure their evaluation will not require any
builds to take place.
)"};
Setting<Strings> allowedUris{this, {}, "allowed-uris",
R"(
A list of URI prefixes to which access is allowed in restricted
evaluation mode. For example, when set to
`https://github.com/NixOS`, builtin functions such as `fetchGit` are
allowed to access `https://github.com/NixOS/patchelf.git`.
)"};
Setting<bool> traceFunctionCalls{this, false, "trace-function-calls",
R"(
If set to `true`, the Nix evaluator will trace every function call.
Nix will print a log message at the "vomit" level for every function
entrance and function exit.
function-trace entered undefined position at 1565795816999559622
function-trace exited undefined position at 1565795816999581277
function-trace entered /nix/store/.../example.nix:226:41 at 1565795253249935150
function-trace exited /nix/store/.../example.nix:226:41 at 1565795253249941684
The `undefined position` means the function call is a builtin.
Use the `contrib/stack-collapse.py` script distributed with the Nix
source code to convert the trace logs in to a format suitable for
`flamegraph.pl`.
)"};
Setting<bool> useEvalCache{this, true, "eval-cache",
"Whether to use the flake evaluation cache."};
};
extern EvalSettings evalSettings;
static const std::string corepkgsPrefix{"/__corepkgs__/"};
}
#include "eval-inline.hh"