forked from lix-project/lix
dcc37c236c
immediately add the result as a permanent GC root. This is the only
way to prevent a race with the garbage collector. For instance, the
old style
ln -s $(nix-store -r $(nix-instantiate foo.nix)) \
/nix/var/nix/gcroots/result
has two time windows in which the garbage collector can interfere
(by GC'ing the derivation and the output, respectively). On the
other hand,
nix-store --add-root /nix/var/nix/gcroots/result -r \
$(nix-instantiate --add-root /nix/var/nix/gcroots/drv \
foo.nix)
is safe.
* nix-build: use `--add-root' to prevent GC races.
141 lines
3.4 KiB
C++
141 lines
3.4 KiB
C++
#include <map>
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#include <iostream>
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#include "globals.hh"
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#include "build.hh"
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#include "gc.hh"
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#include "shared.hh"
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#include "eval.hh"
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#include "parser.hh"
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#include "nixexpr-ast.hh"
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#include "help.txt.hh"
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void printHelp()
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{
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cout << string((char *) helpText, sizeof helpText);
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}
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static Expr evalStdin(EvalState & state, bool parseOnly)
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{
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startNest(nest, lvlTalkative, format("evaluating standard input"));
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string s, s2;
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while (getline(cin, s2)) s += s2 + "\n";
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Expr e = parseExprFromString(state, s, absPath("."));
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return parseOnly ? e : evalExpr(state, e);
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}
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static Path gcRoot;
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static int rootNr = 0;
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/* Print out the paths of the resulting derivation(s). If the user
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specified the `--add-root' flag, we register the derivation as a
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garbage collection root and print out the path of the GC root
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symlink instead. */
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static void printDrvPaths(EvalState & state, Expr e)
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{
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ATermList es;
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/* !!! duplication w.r.t. parseDerivations in nix-env */
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if (matchAttrs(e, es)) {
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Expr a = queryAttr(e, "type");
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if (a && evalString(state, a) == "derivation") {
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a = queryAttr(e, "drvPath");
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if (a) {
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Path drvPath = evalPath(state, a);
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if (gcRoot == "")
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printGCWarning();
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else
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drvPath = addPermRoot(drvPath,
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makeRootName(gcRoot, rootNr));
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cout << format("%1%\n") % drvPath;
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return;
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}
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throw Error("bad derivation");
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} else {
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ATermMap drvMap;
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queryAllAttrs(e, drvMap);
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for (ATermIterator i(drvMap.keys()); i; ++i)
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printDrvPaths(state, evalExpr(state, drvMap.get(*i)));
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return;
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}
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}
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if (matchList(e, es)) {
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for (ATermIterator i(es); i; ++i)
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printDrvPaths(state, evalExpr(state, *i));
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return;
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}
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throw Error("expression does not evaluate to one or more derivations");
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}
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static void printResult(EvalState & state, Expr e, bool evalOnly)
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{
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if (evalOnly)
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cout << format("%1%\n") % e;
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else
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printDrvPaths(state, e);
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}
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void run(Strings args)
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{
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EvalState state;
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Strings files;
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bool readStdin = false;
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bool evalOnly = false;
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bool parseOnly = false;
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for (Strings::iterator i = args.begin();
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i != args.end(); )
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{
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string arg = *i++;
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if (arg == "-")
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readStdin = true;
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else if (arg == "--eval-only") {
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readOnlyMode = true;
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evalOnly = true;
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}
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else if (arg == "--parse-only") {
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readOnlyMode = true;
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parseOnly = evalOnly = true;
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}
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else if (arg == "--add-root") {
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if (i == args.end())
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throw UsageError("`--add-root requires an argument");
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gcRoot = *i++;
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}
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else if (arg[0] == '-')
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throw UsageError(format("unknown flag `%1%`") % arg);
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else
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files.push_back(arg);
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}
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openDB();
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if (readStdin) {
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Expr e = evalStdin(state, parseOnly);
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printResult(state, e, evalOnly);
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}
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for (Strings::iterator i = files.begin();
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i != files.end(); i++)
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{
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Expr e = evalFile(state, absPath(*i));
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/* !!! parseOnly ignored */
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printResult(state, e, evalOnly);
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}
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printEvalStats(state);
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}
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string programId = "nix-instantiate";
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