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lix/src/nix/repl.cc
Eelco Dolstra 0629601da1
Move EvalState from the stack to the heap 
EvalState contains a few counters (e.g. nrValues) that increase
quickly enough that they end up being interpreted as pointers by the
garbage collector. Moving it to the heap makes them invisible to the
garbage collector.

This reduces the max RSS doing 100 evaluations of
nixos.tests.firefox.x86_64-linux.drvPath from 455 MiB to 292 MiB.

Note: ideally, allocations would be much further up in the 64-bit
address space to reduce the odds of an integer being misinterpreted as
a pointer. Maybe we can use some linker magic to move the .bss segment
to a higher address.
2018-06-12 17:49:55 +02:00

704 lines
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#include <iostream>
#include <cstdlib>
#include <setjmp.h>
#include "shared.hh"
#include "eval.hh"
#include "eval-inline.hh"
#include "store-api.hh"
#include "common-eval-args.hh"
#include "get-drvs.hh"
#include "derivations.hh"
#include "affinity.hh"
#include "globals.hh"
#include "command.hh"
#include "finally.hh"
#include "src/linenoise/linenoise.h"
namespace nix {
#define ESC_RED "\033[31m"
#define ESC_GRE "\033[32m"
#define ESC_YEL "\033[33m"
#define ESC_BLU "\033[34;1m"
#define ESC_MAG "\033[35m"
#define ESC_CYA "\033[36m"
#define ESC_END "\033[0m"
struct NixRepl
{
string curDir;
EvalState state;
Strings loadedFiles;
const static int envSize = 32768;
StaticEnv staticEnv;
Env * env;
int displ;
StringSet varNames;
const Path historyFile;
NixRepl(const Strings & searchPath, nix::ref<Store> store);
~NixRepl();
void mainLoop(const std::vector<std::string> & files);
StringSet completePrefix(string prefix);
bool getLine(string & input, const std::string &prompt);
Path getDerivationPath(Value & v);
bool processLine(string line);
void loadFile(const Path & path);
void initEnv();
void reloadFiles();
void addAttrsToScope(Value & attrs);
void addVarToScope(const Symbol & name, Value & v);
Expr * parseString(string s);
void evalString(string s, Value & v);
typedef set<Value *> ValuesSeen;
std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth);
std::ostream & printValue(std::ostream & str, Value & v, unsigned int maxDepth, ValuesSeen & seen);
};
void printHelp()
{
std::cout
<< "Usage: nix-repl [--help] [--version] [-I path] paths...\n"
<< "\n"
<< "nix-repl is a simple read-eval-print loop (REPL) for the Nix package manager.\n"
<< "\n"
<< "Options:\n"
<< " --help\n"
<< " Prints out a summary of the command syntax and exits.\n"
<< "\n"
<< " --version\n"
<< " Prints out the Nix version number on standard output and exits.\n"
<< "\n"
<< " -I path\n"
<< " Add a path to the Nix expression search path. This option may be given\n"
<< " multiple times. See the NIX_PATH environment variable for information on\n"
<< " the semantics of the Nix search path. Paths added through -I take\n"
<< " precedence over NIX_PATH.\n"
<< "\n"
<< " paths...\n"
<< " A list of paths to files containing Nix expressions which nix-repl will\n"
<< " load and add to its scope.\n"
<< "\n"
<< " A path surrounded in < and > will be looked up in the Nix expression search\n"
<< " path, as in the Nix language itself.\n"
<< "\n"
<< " If an element of paths starts with http:// or https://, it is interpreted\n"
<< " as the URL of a tarball that will be downloaded and unpacked to a temporary\n"
<< " location. The tarball must include a single top-level directory containing\n"
<< " at least a file named default.nix.\n";
}
string removeWhitespace(string s)
{
s = chomp(s);
size_t n = s.find_first_not_of(" \n\r\t");
if (n != string::npos) s = string(s, n);
return s;
}
NixRepl::NixRepl(const Strings & searchPath, nix::ref<Store> store)
: state(searchPath, store)
, staticEnv(false, &state.staticBaseEnv)
, historyFile(getDataDir() + "/nix/repl-history")
{
curDir = absPath(".");
}
NixRepl::~NixRepl()
{
linenoiseHistorySave(historyFile.c_str());
}
static NixRepl * curRepl; // ugly
static void completionCallback(const char * s, linenoiseCompletions *lc)
{
/* Otherwise, return all symbols that start with the prefix. */
for (auto & c : curRepl->completePrefix(s))
linenoiseAddCompletion(lc, c.c_str());
}
void NixRepl::mainLoop(const std::vector<std::string> & files)
{
string error = ANSI_RED "error:" ANSI_NORMAL " ";
std::cout << "Welcome to Nix version " << nixVersion << ". Type :? for help." << std::endl << std::endl;
for (auto & i : files)
loadedFiles.push_back(i);
reloadFiles();
if (!loadedFiles.empty()) std::cout << std::endl;
createDirs(dirOf(historyFile));
linenoiseHistorySetMaxLen(1000);
linenoiseHistoryLoad(historyFile.c_str());
curRepl = this;
linenoiseSetCompletionCallback(completionCallback);
std::string input;
while (true) {
// When continuing input from previous lines, don't print a prompt, just align to the same
// number of chars as the prompt.
if (!getLine(input, input.empty() ? "nix-repl> " : " "))
break;
try {
if (!removeWhitespace(input).empty() && !processLine(input)) return;
} catch (ParseError & e) {
if (e.msg().find("unexpected $end") != std::string::npos) {
// For parse errors on incomplete input, we continue waiting for the next line of
// input without clearing the input so far.
continue;
} else {
printMsg(lvlError, format(error + "%1%%2%") % (settings.showTrace ? e.prefix() : "") % e.msg());
}
} catch (Error & e) {
printMsg(lvlError, format(error + "%1%%2%") % (settings.showTrace ? e.prefix() : "") % e.msg());
} catch (Interrupted & e) {
printMsg(lvlError, format(error + "%1%%2%") % (settings.showTrace ? e.prefix() : "") % e.msg());
}
// We handled the current input fully, so we should clear it
// and read brand new input.
linenoiseHistoryAdd(input.c_str());
input.clear();
std::cout << std::endl;
}
}
bool NixRepl::getLine(string & input, const std::string &prompt)
{
char * s = linenoise(prompt.c_str());
Finally doFree([&]() { free(s); });
if (!s) {
switch (auto type = linenoiseKeyType()) {
case 1: // ctrl-C
input = "";
return true;
case 2: // ctrl-D
return false;
default:
throw Error(format("Unexpected linenoise keytype: %1%") % type);
}
}
input += s;
input += '\n';
return true;
}
StringSet NixRepl::completePrefix(string prefix)
{
StringSet completions;
size_t start = prefix.find_last_of(" \n\r\t(){}[]");
std::string prev, cur;
if (start == std::string::npos) {
prev = "";
cur = prefix;
} else {
prev = std::string(prefix, 0, start + 1);
cur = std::string(prefix, start + 1);
}
size_t slash, dot;
if ((slash = cur.rfind('/')) != string::npos) {
try {
auto dir = std::string(cur, 0, slash);
auto prefix2 = std::string(cur, slash + 1);
for (auto & entry : readDirectory(dir == "" ? "/" : dir)) {
if (entry.name[0] != '.' && hasPrefix(entry.name, prefix2))
completions.insert(prev + dir + "/" + entry.name);
}
} catch (Error &) {
}
} else if ((dot = cur.rfind('.')) == string::npos) {
/* This is a variable name; look it up in the current scope. */
StringSet::iterator i = varNames.lower_bound(cur);
while (i != varNames.end()) {
if (string(*i, 0, cur.size()) != cur) break;
completions.insert(prev + *i);
i++;
}
} else {
try {
/* This is an expression that should evaluate to an
attribute set. Evaluate it to get the names of the
attributes. */
string expr(cur, 0, dot);
string cur2 = string(cur, dot + 1);
Expr * e = parseString(expr);
Value v;
e->eval(state, *env, v);
state.forceAttrs(v);
for (auto & i : *v.attrs) {
string name = i.name;
if (string(name, 0, cur2.size()) != cur2) continue;
completions.insert(prev + expr + "." + name);
}
} catch (ParseError & e) {
// Quietly ignore parse errors.
} catch (EvalError & e) {
// Quietly ignore evaluation errors.
} catch (UndefinedVarError & e) {
// Quietly ignore undefined variable errors.
}
}
return completions;
}
static int runProgram(const string & program, const Strings & args)
{
Strings args2(args);
args2.push_front(program);
Pid pid;
pid = fork();
if (pid == -1) throw SysError("forking");
if (pid == 0) {
restoreAffinity();
execvp(program.c_str(), stringsToCharPtrs(args2).data());
_exit(1);
}
return pid.wait();
}
bool isVarName(const string & s)
{
if (s.size() == 0) return false;
char c = s[0];
if ((c >= '0' && c <= '9') || c == '-' || c == '\'') return false;
for (auto & i : s)
if (!((i >= 'a' && i <= 'z') ||
(i >= 'A' && i <= 'Z') ||
(i >= '0' && i <= '9') ||
i == '_' || i == '-' || i == '\''))
return false;
return true;
}
Path NixRepl::getDerivationPath(Value & v) {
auto drvInfo = getDerivation(state, v, false);
if (!drvInfo)
throw Error("expression does not evaluate to a derivation, so I can't build it");
Path drvPath = drvInfo->queryDrvPath();
if (drvPath == "" || !state.store->isValidPath(drvPath))
throw Error("expression did not evaluate to a valid derivation");
return drvPath;
}
bool NixRepl::processLine(string line)
{
if (line == "") return true;
string command, arg;
if (line[0] == ':') {
size_t p = line.find_first_of(" \n\r\t");
command = string(line, 0, p);
if (p != string::npos) arg = removeWhitespace(string(line, p));
} else {
arg = line;
}
if (command == ":?" || command == ":help") {
std::cout
<< "The following commands are available:\n"
<< "\n"
<< " <expr> Evaluate and print expression\n"
<< " <x> = <expr> Bind expression to variable\n"
<< " :a <expr> Add attributes from resulting set to scope\n"
<< " :b <expr> Build derivation\n"
<< " :i <expr> Build derivation, then install result into current profile\n"
<< " :l <path> Load Nix expression and add it to scope\n"
<< " :p <expr> Evaluate and print expression recursively\n"
<< " :q Exit nix-repl\n"
<< " :r Reload all files\n"
<< " :s <expr> Build dependencies of derivation, then start nix-shell\n"
<< " :t <expr> Describe result of evaluation\n"
<< " :u <expr> Build derivation, then start nix-shell\n";
}
else if (command == ":a" || command == ":add") {
Value v;
evalString(arg, v);
addAttrsToScope(v);
}
else if (command == ":l" || command == ":load") {
state.resetFileCache();
loadFile(arg);
}
else if (command == ":r" || command == ":reload") {
state.resetFileCache();
reloadFiles();
}
else if (command == ":t") {
Value v;
evalString(arg, v);
std::cout << showType(v) << std::endl;
} else if (command == ":u") {
Value v, f, result;
evalString(arg, v);
evalString("drv: (import <nixpkgs> {}).runCommand \"shell\" { buildInputs = [ drv ]; } \"\"", f);
state.callFunction(f, v, result, Pos());
Path drvPath = getDerivationPath(result);
runProgram(settings.nixBinDir + "/nix-shell", Strings{drvPath});
}
else if (command == ":b" || command == ":i" || command == ":s") {
Value v;
evalString(arg, v);
Path drvPath = getDerivationPath(v);
if (command == ":b") {
/* We could do the build in this process using buildPaths(),
but doing it in a child makes it easier to recover from
problems / SIGINT. */
if (runProgram(settings.nixBinDir + "/nix-store", Strings{"-r", drvPath}) == 0) {
Derivation drv = readDerivation(drvPath);
std::cout << std::endl << "this derivation produced the following outputs:" << std::endl;
for (auto & i : drv.outputs)
std::cout << format(" %1% -> %2%") % i.first % i.second.path << std::endl;
}
} else if (command == ":i") {
runProgram(settings.nixBinDir + "/nix-env", Strings{"-i", drvPath});
} else {
runProgram(settings.nixBinDir + "/nix-shell", Strings{drvPath});
}
}
else if (command == ":p" || command == ":print") {
Value v;
evalString(arg, v);
printValue(std::cout, v, 1000000000) << std::endl;
}
else if (command == ":q" || command == ":quit")
return false;
else if (command != "")
throw Error(format("unknown command '%1%'") % command);
else {
size_t p = line.find('=');
string name;
if (p != string::npos &&
p < line.size() &&
line[p + 1] != '=' &&
isVarName(name = removeWhitespace(string(line, 0, p))))
{
Expr * e = parseString(string(line, p + 1));
Value & v(*state.allocValue());
v.type = tThunk;
v.thunk.env = env;
v.thunk.expr = e;
addVarToScope(state.symbols.create(name), v);
} else {
Value v;
evalString(line, v);
printValue(std::cout, v, 1) << std::endl;
}
}
return true;
}
void NixRepl::loadFile(const Path & path)
{
loadedFiles.remove(path);
loadedFiles.push_back(path);
Value v, v2;
state.evalFile(lookupFileArg(state, path), v);
Bindings & bindings(*state.allocBindings(0));
state.autoCallFunction(bindings, v, v2);
addAttrsToScope(v2);
}
void NixRepl::initEnv()
{
env = &state.allocEnv(envSize);
env->up = &state.baseEnv;
displ = 0;
staticEnv.vars.clear();
varNames.clear();
for (auto & i : state.staticBaseEnv.vars)
varNames.insert(i.first);
}
void NixRepl::reloadFiles()
{
initEnv();
Strings old = loadedFiles;
loadedFiles.clear();
bool first = true;
for (auto & i : old) {
if (!first) std::cout << std::endl;
first = false;
std::cout << format("Loading '%1%'...") % i << std::endl;
loadFile(i);
}
}
void NixRepl::addAttrsToScope(Value & attrs)
{
state.forceAttrs(attrs);
for (auto & i : *attrs.attrs)
addVarToScope(i.name, *i.value);
std::cout << format("Added %1% variables.") % attrs.attrs->size() << std::endl;
}
void NixRepl::addVarToScope(const Symbol & name, Value & v)
{
if (displ >= envSize)
throw Error("environment full; cannot add more variables");
staticEnv.vars[name] = displ;
env->values[displ++] = &v;
varNames.insert((string) name);
}
Expr * NixRepl::parseString(string s)
{
Expr * e = state.parseExprFromString(s, curDir, staticEnv);
return e;
}
void NixRepl::evalString(string s, Value & v)
{
Expr * e = parseString(s);
e->eval(state, *env, v);
state.forceValue(v);
}
std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int maxDepth)
{
ValuesSeen seen;
return printValue(str, v, maxDepth, seen);
}
std::ostream & printStringValue(std::ostream & str, const char * string) {
str << "\"";
for (const char * i = string; *i; i++)
if (*i == '\"' || *i == '\\') str << "\\" << *i;
else if (*i == '\n') str << "\\n";
else if (*i == '\r') str << "\\r";
else if (*i == '\t') str << "\\t";
else str << *i;
str << "\"";
return str;
}
// FIXME: lot of cut&paste from Nix's eval.cc.
std::ostream & NixRepl::printValue(std::ostream & str, Value & v, unsigned int maxDepth, ValuesSeen & seen)
{
str.flush();
checkInterrupt();
state.forceValue(v);
switch (v.type) {
case tInt:
str << ESC_CYA << v.integer << ESC_END;
break;
case tBool:
str << ESC_CYA << (v.boolean ? "true" : "false") << ESC_END;
break;
case tString:
str << ESC_YEL;
printStringValue(str, v.string.s);
str << ESC_END;
break;
case tPath:
str << ESC_GRE << v.path << ESC_END; // !!! escaping?
break;
case tNull:
str << ESC_CYA "null" ESC_END;
break;
case tAttrs: {
seen.insert(&v);
bool isDrv = state.isDerivation(v);
if (isDrv) {
str << "«derivation ";
Bindings::iterator i = v.attrs->find(state.sDrvPath);
PathSet context;
Path drvPath = i != v.attrs->end() ? state.coerceToPath(*i->pos, *i->value, context) : "???";
str << drvPath << "»";
}
else if (maxDepth > 0) {
str << "{ ";
typedef std::map<string, Value *> Sorted;
Sorted sorted;
for (auto & i : *v.attrs)
sorted[i.name] = i.value;
/* If this is a derivation, then don't show the
self-references ("all", "out", etc.). */
StringSet hidden;
if (isDrv) {
hidden.insert("all");
Bindings::iterator i = v.attrs->find(state.sOutputs);
if (i == v.attrs->end())
hidden.insert("out");
else {
state.forceList(*i->value);
for (unsigned int j = 0; j < i->value->listSize(); ++j)
hidden.insert(state.forceStringNoCtx(*i->value->listElems()[j]));
}
}
for (auto & i : sorted) {
if (isVarName(i.first))
str << i.first;
else
printStringValue(str, i.first.c_str());
str << " = ";
if (hidden.find(i.first) != hidden.end())
str << "«...»";
else if (seen.find(i.second) != seen.end())
str << "«repeated»";
else
try {
printValue(str, *i.second, maxDepth - 1, seen);
} catch (AssertionError & e) {
str << ESC_RED "«error: " << e.msg() << "»" ESC_END;
}
str << "; ";
}
str << "}";
} else
str << "{ ... }";
break;
}
case tList1:
case tList2:
case tListN:
seen.insert(&v);
str << "[ ";
if (maxDepth > 0)
for (unsigned int n = 0; n < v.listSize(); ++n) {
if (seen.find(v.listElems()[n]) != seen.end())
str << "«repeated»";
else
try {
printValue(str, *v.listElems()[n], maxDepth - 1, seen);
} catch (AssertionError & e) {
str << ESC_RED "«error: " << e.msg() << "»" ESC_END;
}
str << " ";
}
else
str << "... ";
str << "]";
break;
case tLambda: {
std::ostringstream s;
s << v.lambda.fun->pos;
str << ESC_BLU "«lambda @ " << filterANSIEscapes(s.str()) << "»" ESC_END;
break;
}
case tPrimOp:
str << ESC_MAG "«primop»" ESC_END;
break;
case tPrimOpApp:
str << ESC_BLU "«primop-app»" ESC_END;
break;
case tFloat:
str << v.fpoint;
break;
default:
str << ESC_RED "«unknown»" ESC_END;
break;
}
return str;
}
struct CmdRepl : StoreCommand, MixEvalArgs
{
std::vector<std::string> files;
CmdRepl()
{
expectArgs("files", &files);
}
std::string name() override { return "repl"; }
std::string description() override
{
return "start an interactive environment for evaluating Nix expressions";
}
void run(ref<Store> store) override
{
auto repl = std::make_unique<NixRepl>(searchPath, openStore());
repl->mainLoop(files);
}
};
static RegisterCommand r1(make_ref<CmdRepl>());
}
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