nix-build: Port to c++

This was a dumb line-for-line rewrite, because nix build/nix run/etc.
will replace it.

src/nix-build/nix-build.cc

@@ -0,0 +1,482 @@
+#include <cstring>
+#include <regex>
+#include "util.hh"
+#include <unistd.h>
+#include "shared.hh"
+#include <sstream>
+#include <vector>
+#include <iostream>
+#include <fstream>
+#include "store-api.hh"
+#include "globals.hh"
+#include "derivations.hh"
+
+using namespace nix;
+using std::stringstream;
+
+extern char ** environ;
+
+std::vector<string> shellwords(const string & s)
+{
+    auto whitespace = std::regex("^(\\s+).*");
+    auto begin = s.cbegin();
+    auto res = std::vector<string>{};
+    auto cur = stringstream{};
+    enum state {
+        sBegin,
+        sQuote
+    };
+    state st = sBegin;
+    auto it = begin;
+    for (; it != s.cend(); ++it) {
+        if (st == sBegin) {
+            auto match = std::smatch{};
+            if (regex_search(it, s.cend(), match, whitespace)) {
+                cur << string(begin, it);
+                res.push_back(cur.str());
+                cur = stringstream{};
+                it = match[1].second;
+                begin = it;
+            }
+        }
+        switch (*it) {
+            case '"':
+                cur << string(begin, it);
+                begin = it + 1;
+                st = st == sBegin ? sQuote : sBegin;
+                break;
+            case '\\':
+                /* perl shellwords mostly just treats the next char as part of the string with no special processing */
+                cur << string(begin, it);
+                begin = ++it;
+                break;
+        }
+    }
+    cur << string(begin, it);
+    auto last = cur.str();
+    if (!last.empty()) {
+        res.push_back(std::move(last));
+    }
+    return res;
+}
+
+int main(int argc, char ** argv)
+{
+    return handleExceptions(argv[0], [&]() {
+        initNix();
+        auto store = openStore();
+        auto dryRun = false;
+        auto verbose = false;
+        auto runEnv = std::regex_search(argv[0], std::regex("nix-shell$"));
+        auto pure = false;
+        auto fromArgs = false;
+        auto packages = false;
+        auto interactive = true;
+
+        auto instArgs = Strings{};
+        auto buildArgs = Strings{};
+        auto exprs = Strings{};
+
+        auto shell = getEnv("SHELL", "/bin/sh");
+        auto envCommand = string{}; // interactive shell
+        auto envExclude = Strings{};
+
+        auto myName = runEnv ? "nix-shell" : "nix-build";
+
+        auto inShebang = false;
+        auto script = string{};
+        auto savedArgs = std::vector<string>{};
+
+        auto tmpDir = AutoDelete{createTempDir("", myName)};
+
+        auto outLink = string("./result");
+        auto drvLink = (Path) tmpDir + "/derivation";
+
+        auto args = std::vector<string>{};
+        for (int i = 1; i < argc; ++i)
+            args.push_back(argv[i]);
+        // Heuristic to see if we're invoked as a shebang script, namely, if we
+        // have a single argument, it's the name of an executable file, and it
+        // starts with "#!".
+        if (runEnv && argc > 1 && !std::regex_search(argv[1], std::regex("nix-shell"))) {
+            script = argv[1];
+            if (access(script.c_str(), F_OK) == 0 && access(script.c_str(), X_OK) == 0) {
+                auto SCRIPT = std::ifstream(script);
+                string first;
+                std::getline(SCRIPT, first);
+                if (std::regex_search(first, std::regex("^#!"))) {
+                    inShebang = true;
+                    for (int i = 2; i < argc - 1; ++i)
+                        savedArgs.push_back(argv[i]);
+                    args = std::vector<string>{};
+                    for (string line; std::getline(SCRIPT, line);) {
+                        line = chomp(line);
+                        std::smatch match;
+                        if (std::regex_match(line, match, std::regex("^#!\\s*nix-shell (.*)$")))
+                            for (const auto & word : shellwords(match[1].str()))
+                                args.push_back(word);
+                    }
+                }
+            }
+        }
+
+        for (auto n = decltype(args)::size_type{0}; n < args.size(); ++n) {
+            auto arg = args[n];
+
+            if (arg == "--help") {
+                deletePath(tmpDir);
+                tmpDir.cancel();
+                execlp("man", "man", myName, NULL);
+                throw SysError("executing man");
+            }
+
+            else if (arg == "--version") {
+                std::cout << myName << " (Nix) " << nixVersion << '\n';
+                return;
+            }
+
+            else if (arg == "--add-drv-link") {
+                drvLink = "./derivation";
+            }
+
+            else if (arg == "--no-out-link" || arg == "--no-link") {
+                outLink = (Path) tmpDir + "/result";
+            }
+
+            else if (arg == "--drv-link") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError("--drv-link requires an argument");
+                }
+                drvLink = args[n];
+            }
+
+            else if (arg == "--out-link" || arg == "-o") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError(format("%1% requires an argument") % arg);
+                }
+                outLink = args[n];
+            }
+
+            else if (arg == "--attr" || arg == "-A" || arg == "-I") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError(format("%1% requires an argument") % arg);
+                }
+                instArgs.push_back(arg);
+                instArgs.push_back(args[n]);
+            }
+
+            else if (arg == "--arg" || arg == "--argstr") {
+                if (n + 2 >= args.size()) {
+                    throw UsageError(format("%1% requires two arguments") % arg);
+                }
+                instArgs.push_back(arg);
+                instArgs.push_back(args[n + 1]);
+                instArgs.push_back(args[n + 2]);
+                n += 2;
+            }
+
+            else if (arg == "--option") {
+                if (n + 2 >= args.size()) {
+                    throw UsageError(format("%1% requires two arguments") % arg);
+                }
+                instArgs.push_back(arg);
+                instArgs.push_back(args[n + 1]);
+                instArgs.push_back(args[n + 2]);
+                buildArgs.push_back(arg);
+                buildArgs.push_back(args[n + 1]);
+                buildArgs.push_back(args[n + 2]);
+                n += 2;
+            }
+
+            else if (arg == "--max-jobs" || arg == "-j" || arg == "--max-silent-time" || arg == "--cores" || arg == "--timeout" || arg == "--add-root") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError(format("%1% requires an argument") % arg);
+                }
+                buildArgs.push_back(arg);
+                buildArgs.push_back(args[n]);
+            }
+
+            else if (arg == "--dry-run") {
+                buildArgs.push_back("--dry-run");
+                dryRun = true;
+            }
+
+            else if (arg == "--show-trace") {
+                instArgs.push_back(arg);
+            }
+
+            else if (arg == "-") {
+                exprs = Strings{"-"};
+            }
+
+            else if (arg == "--verbose" || (arg.size() >= 2 && arg.substr(0, 2) == "-v")) {
+                buildArgs.push_back(arg);
+                instArgs.push_back(arg);
+                verbose = true;
+            }
+
+            else if (arg == "--quiet" || arg == "--repair") {
+                buildArgs.push_back(arg);
+                instArgs.push_back(arg);
+            }
+
+            else if (arg == "--check") {
+                buildArgs.push_back(arg);
+            }
+
+            else if (arg == "--run-env") { // obsolete
+                runEnv = true;
+            }
+
+            else if (arg == "--command" || arg == "--run") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError(format("%1% requires an argument") % arg);
+                }
+                envCommand = args[n] + "\nexit";
+                if (arg == "--run")
+                    interactive = false;
+            }
+
+            else if (arg == "--exclude") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError(format("%1% requires an argument") % arg);
+                }
+                envExclude.push_back(args[n]);
+            }
+
+            else if (arg == "--pure") { pure = true; }
+            else if (arg == "--impure") { pure = false; }
+
+            else if (arg == "--expr" || arg == "-E") {
+                fromArgs = true;
+                instArgs.push_back("--expr");
+            }
+
+            else if (arg == "--packages" || arg == "-p") {
+                packages = true;
+            }
+
+            else if (inShebang && arg == "-i") {
+                n++;
+                if (n >= args.size()) {
+                    throw UsageError(format("%1% requires an argument") % arg);
+                }
+                auto interpreter = args[n];
+                auto execArgs = "";
+
+                auto shellEscape = [](const string & s) {
+                    return "'" + std::regex_replace(s, std::regex("'"), "'\\''") + "'";
+                };
+
+                // Überhack to support Perl. Perl examines the shebang and
+                // executes it unless it contains the string "perl" or "indir",
+                // or (undocumented) argv[0] does not contain "perl". Exploit
+                // the latter by doing "exec -a".
+                if (std::regex_search(interpreter, std::regex("perl"))) {
+                        execArgs = "-a PERL";
+                }
+
+                auto joined = stringstream{};
+                for (const auto & i : savedArgs)
+                    joined << shellEscape(i) << ' ';
+
+                if (std::regex_search(interpreter, std::regex("ruby"))) {
+                    // Hack for Ruby. Ruby also examines the shebang. It tries to
+                    // read the shebang to understand which packages to read from. Since
+                    // this is handled via nix-shell -p, we wrap our ruby script execution
+                    // in ruby -e 'load' which ignores the shebangs.
+
+                    envCommand = (format("exec %1% %2% -e 'load(\"%3%\") -- %4%") % execArgs % interpreter % script % joined.str()).str();
+                } else {
+                    envCommand = (format("exec %1% %2% %3% %4%") % execArgs % interpreter % script % joined.str()).str();
+                }
+            }
+
+            else if (!arg.empty() && arg[0] == '-') {
+                buildArgs.push_back(arg);
+            }
+
+            else if (arg == "-Q" || arg == "--no-build-output") {
+                buildArgs.push_back(arg);
+                instArgs.push_back(arg);
+            }
+
+            else {
+                exprs.push_back(arg);
+            }
+        }
+
+        if (packages && fromArgs) {
+            throw UsageError("‘-p’ and ‘-E’ are mutually exclusive");
+        }
+
+        if (packages) {
+            instArgs.push_back("--expr");
+            auto joined = stringstream{};
+            joined << "with import <nixpkgs> { }; runCommand \"shell\" { buildInputs = [ ";
+            for (const auto & i : exprs)
+                joined << '(' << i << ") ";
+            joined << "]; } \"\"";
+            exprs = Strings{joined.str()};
+        } else if (!fromArgs) {
+            if (exprs.empty() && runEnv && access("shell.nix", F_OK) == 0)
+                exprs.push_back("shell.nix");
+            if (exprs.empty())
+                exprs.push_back("default.nix");
+        }
+
+        if (runEnv)
+            setenv("IN_NIX_SHELL", "1", 1);
+
+        for (auto & expr : exprs) {
+            // Instantiate.
+            auto drvPaths = std::vector<string>{};
+            if (!std::regex_match(expr, std::regex("^/.*\\.drv$"))) {
+                // If we're in a #! script, interpret filenames relative to the
+                // script.
+                if (inShebang && !packages)
+                    expr = absPath(expr, dirOf(script));
+
+                auto instantiateArgs = Strings{"--add-root", drvLink, "--indirect"};
+                for (const auto & arg : instArgs)
+                    instantiateArgs.push_back(arg);
+                instantiateArgs.push_back(expr);
+                auto instOutput = runProgram(settings.nixBinDir + "/nix-instantiate", false, instantiateArgs);
+                drvPaths = tokenizeString<std::vector<string>>(instOutput);
+            } else {
+                drvPaths.push_back(expr);
+            }
+
+            if (runEnv) {
+                if (drvPaths.size() != 1)
+                    throw UsageError("a single derivation is required");
+                auto drvPath = drvPaths[0];
+                drvPath = drvPath.substr(0, drvPath.find_first_of('!'));
+                if (isLink(drvPath))
+                    drvPath = readLink(drvPath);
+                auto drv = store->derivationFromPath(drvPath);
+
+                // Build or fetch all dependencies of the derivation.
+                auto nixStoreArgs = Strings{"-r", "--no-output", "--no-gc-warning"};
+                for (const auto & arg : buildArgs)
+                    nixStoreArgs.push_back(arg);
+                for (const auto & input : drv.inputDrvs)
+                    if (std::all_of(envExclude.cbegin(), envExclude.cend(), [&](const string & exclude) { return !std::regex_search(input.first, std::regex(exclude)); }))
+                        nixStoreArgs.push_back(input.first);
+                for (const auto & src : drv.inputSrcs)
+                    nixStoreArgs.push_back(src);
+                runProgram(settings.nixBinDir + "/nix-store", false, nixStoreArgs);
+
+                // Set the environment.
+                auto tmp = getEnv("TMPDIR", getEnv("XDG_RUNTIME_DIR", "/tmp"));
+                if (pure) {
+                    auto skippedEnv = std::vector<string>{"HOME", "USER", "LOGNAME", "DISPLAY", "PATH", "TERM", "IN_NIX_SHELL", "TZ", "PAGER", "NIX_BUILD_SHELL"};
+                    auto removed = std::vector<string>{};
+                    for (auto i = size_t{0}; environ[i]; ++i) {
+                        auto eq = strchr(environ[i], '=');
+                        if (!eq)
+                            // invalid env, just keep going
+                            continue;
+                        auto name = string(environ[i], eq);
+                        if (find(skippedEnv.begin(), skippedEnv.end(), name) == skippedEnv.end())
+                            removed.emplace_back(std::move(name));
+                    }
+                    for (const auto & name : removed)
+                        unsetenv(name.c_str());
+                    // NixOS hack: prevent /etc/bashrc from sourcing /etc/profile.
+                    setenv("__ETC_PROFILE_SOURCED", "1", 1);
+                }
+                setenv("NIX_BUILD_TOP", tmp.c_str(), 1);
+                setenv("TMPDIR", tmp.c_str(), 1);
+                setenv("TEMPDIR", tmp.c_str(), 1);
+                setenv("TMP", tmp.c_str(), 1);
+                setenv("TEMP", tmp.c_str(), 1);
+                setenv("NIX_STORE", store->storeDir.c_str(), 1);
+                for (const auto & env : drv.env)
+                    setenv(env.first.c_str(), env.second.c_str(), 1);
+
+                // Run a shell using the derivation's environment.  For
+                // convenience, source $stdenv/setup to setup additional
+                // environment variables and shell functions.  Also don't lose
+                // the current $PATH directories.
+                auto rcfile = (Path) tmpDir + "/rc";
+                writeFile(rcfile, (format(
+                        "rm -rf '%1%'; "
+                        "unset BASH_ENV; "
+                        "[ -n \"$PS1\" ] && [ -e ~/.bashrc ] && source ~/.bashrc; "
+                        "%2%"
+                        "dontAddDisableDepTrack=1; "
+                        "[ -e $stdenv/setup ] && source $stdenv/setup; "
+                        "%3%"
+                        "set +e; "
+                        "[ -n \"$PS1\" ] && PS1=\"\\n\\[\\033[1;32m\\][nix-shell:\\w]$\\[\\033[0m\\] \"; "
+                        "if [ \"$(type -t runHook)\" = function ]; then runHook shellHook; fi; "
+                        "unset NIX_ENFORCE_PURITY; "
+                        "unset NIX_INDENT_MAKE; "
+                        "shopt -u nullglob; "
+                        "unset TZ; %4%"
+                        "%5%"
+                        ) % (Path) tmpDir % (pure ? "" : "p=$PATH") % (pure ? "" : "PATH=$PATH:$p; unset p; ") % (getenv("TZ") ? (string("export TZ='") + getenv("TZ") + "'; ") : "") % envCommand).str());
+                setenv("BASH_ENV", rcfile.c_str(), 1);
+                if (interactive)
+                    execlp(getEnv("NIX_BUILD_SHELL", "bash").c_str(), "bash", "--rcfile", rcfile.c_str(), NULL);
+                else
+                    execlp(getEnv("NIX_BUILD_SHELL", "bash").c_str(), "bash", rcfile.c_str(), NULL);
+                throw SysError("executing shell");
+            }
+
+            // Ugly hackery to make "nix-build -A foo.all" produce symlinks
+            // ./result, ./result-dev, and so on, rather than ./result,
+            // ./result-2-dev, and so on.  This combines multiple derivation
+            // paths into one "/nix/store/drv-path!out1,out2,..." argument.
+            auto prevDrvPath = string{};
+            auto drvPaths2 = Strings{};
+            for (const auto & drvPath : drvPaths) {
+                auto p = drvPath;
+                auto output = string{"out"};
+                std::smatch match;
+                if (std::regex_match(drvPath, match, std::regex("(.*)!(.*)"))) {
+                    p = match[1].str();
+                    output = match[2].str();
+                }
+                auto target = readLink(p);
+                if (verbose)
+                    std::cerr << "derivation is " << target << '\n';
+                if (target == prevDrvPath) {
+                    auto last = drvPaths2.back();
+                    drvPaths2.pop_back();
+                    drvPaths2.push_back(last + "," + output);
+                } else {
+                    drvPaths2.push_back(target + "!" + output);
+                    prevDrvPath = target;
+                }
+            }
+            // Build.
+            auto outPaths = Strings{};
+            auto nixStoreArgs = Strings{"--add-root", outLink, "--indirect", "-r"};
+            for (const auto & arg : buildArgs)
+                nixStoreArgs.push_back(arg);
+            for (const auto & path : drvPaths2)
+                nixStoreArgs.push_back(path);
+            auto nixStoreRes = runProgram(settings.nixBinDir + "/nix-store", false, nixStoreArgs);
+            for (const auto & outpath : tokenizeString<std::vector<string>>(nixStoreRes)) {
+                outPaths.push_back(chomp(outpath));
+            }
+
+            if (dryRun)
+                continue;
+            for (const auto & outPath : outPaths) {
+                auto target = readLink(outPath);
+                std::cout << target << '\n';
+            }
+        }
+        return;
+    });
+}
+