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Move NIX_BIN_DIR and all logic using it to the Nix executable itself
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This is because with the split packages of the Meson build, we simply
have no idea what directory the binaries will be installed in when we
build the library.

In the process of doing so, consolidate and make more sophisticated the
logic to cope with a few corner cases (e.g. `NIX_BIN_DIR` exists, but no
binaries are inside it).
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Ericson2314 committed Jul 25, 2024
1 parent dba1142 commit df11dd3
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Showing 14 changed files with 158 additions and 71 deletions.
38 changes: 17 additions & 21 deletions src/libcmd/repl.cc
Original file line number Diff line number Diff line change
Expand Up @@ -7,7 +7,6 @@

#include "ansicolor.hh"
#include "shared.hh"
#include "config-global.hh"
#include "eval.hh"
#include "eval-settings.hh"
#include "attr-path.hh"
Expand Down Expand Up @@ -77,10 +76,14 @@ struct NixRepl
int displ;
StringSet varNames;

RunNix * runNixPtr;

void runNix(Path program, const Strings & args, const std::optional<std::string> & input = {});

std::unique_ptr<ReplInteracter> interacter;

NixRepl(const LookupPath & lookupPath, nix::ref<Store> store,ref<EvalState> state,
std::function<AnnotatedValues()> getValues);
std::function<AnnotatedValues()> getValues, RunNix * runNix);
virtual ~NixRepl() = default;

ReplExitStatus mainLoop() override;
Expand Down Expand Up @@ -125,32 +128,16 @@ std::string removeWhitespace(std::string s)


NixRepl::NixRepl(const LookupPath & lookupPath, nix::ref<Store> store, ref<EvalState> state,
std::function<NixRepl::AnnotatedValues()> getValues)
std::function<NixRepl::AnnotatedValues()> getValues, RunNix * runNix = nullptr)
: AbstractNixRepl(state)
, debugTraceIndex(0)
, getValues(getValues)
, staticEnv(new StaticEnv(nullptr, state->staticBaseEnv.get()))
, runNixPtr{runNix}
, interacter(make_unique<ReadlineLikeInteracter>(getDataDir() + "/nix/repl-history"))
{
}

void runNix(Path program, const Strings & args,
const std::optional<std::string> & input = {})
{
auto subprocessEnv = getEnv();
subprocessEnv["NIX_CONFIG"] = globalConfig.toKeyValue();
//isInteractive avoid grabling interactive commands
runProgram2(RunOptions {
.program = settings.nixBinDir+ "/" + program,
.args = args,
.environment = subprocessEnv,
.input = input,
.isInteractive = true,
});

return;
}

static std::ostream & showDebugTrace(std::ostream & out, const PosTable & positions, const DebugTrace & dt)
{
if (dt.isError)
Expand Down Expand Up @@ -836,9 +823,18 @@ void NixRepl::evalString(std::string s, Value & v)
}


void NixRepl::runNix(Path program, const Strings & args, const std::optional<std::string> & input)
{
if (runNixPtr)
(*runNixPtr)(program, args, input);
else
throw Error("Cannot run '%s', no method of calling the Nix CLI provided", program);
}


std::unique_ptr<AbstractNixRepl> AbstractNixRepl::create(
const LookupPath & lookupPath, nix::ref<Store> store, ref<EvalState> state,
std::function<AnnotatedValues()> getValues)
std::function<AnnotatedValues()> getValues, RunNix * runNix)
{
return std::make_unique<NixRepl>(
lookupPath,
Expand Down
14 changes: 12 additions & 2 deletions src/libcmd/repl.hh
Original file line number Diff line number Diff line change
Expand Up @@ -19,9 +19,19 @@ struct AbstractNixRepl

typedef std::vector<std::pair<Value*,std::string>> AnnotatedValues;

using RunNix = void(Path program, const Strings & args, const std::optional<std::string> & input);

/**
* @param runNix Function to run the nix CLI to support various
* `:<something>` commands. Can not be provided, in which case
* everything else will still work fine, but those commands won't.
*/
static std::unique_ptr<AbstractNixRepl> create(
const LookupPath & lookupPath, nix::ref<Store> store, ref<EvalState> state,
std::function<AnnotatedValues()> getValues);
const LookupPath & lookupPath,
nix::ref<Store> store,
ref<EvalState> state,
std::function<AnnotatedValues()> getValues,
RunNix * runNix = nullptr);

static ReplExitStatus runSimple(
ref<EvalState> evalState,
Expand Down
29 changes: 0 additions & 29 deletions src/libstore/globals.cc
Original file line number Diff line number Diff line change
Expand Up @@ -64,7 +64,6 @@ Settings::Settings()
, nixStateDir(canonPath(getEnvNonEmpty("NIX_STATE_DIR").value_or(NIX_STATE_DIR)))
, nixConfDir(canonPath(getEnvNonEmpty("NIX_CONF_DIR").value_or(NIX_CONF_DIR)))
, nixUserConfFiles(getUserConfigFiles())
, nixBinDir(canonPath(getEnvNonEmpty("NIX_BIN_DIR").value_or(NIX_BIN_DIR)))
, nixManDir(canonPath(NIX_MAN_DIR))
, nixDaemonSocketFile(canonPath(getEnvNonEmpty("NIX_DAEMON_SOCKET_PATH").value_or(nixStateDir + DEFAULT_SOCKET_PATH)))
{
Expand Down Expand Up @@ -95,34 +94,6 @@ Settings::Settings()
sandboxPaths = tokenizeString<StringSet>("/System/Library/Frameworks /System/Library/PrivateFrameworks /bin/sh /bin/bash /private/tmp /private/var/tmp /usr/lib");
allowedImpureHostPrefixes = tokenizeString<StringSet>("/System/Library /usr/lib /dev /bin/sh");
#endif

/* Set the build hook location
For builds we perform a self-invocation, so Nix has to be self-aware.
That is, it has to know where it is installed. We don't think it's sentient.
Normally, nix is installed according to `nixBinDir`, which is set at compile time,
but can be overridden. This makes for a great default that works even if this
code is linked as a library into some other program whose main is not aware
that it might need to be a build remote hook.
However, it may not have been installed at all. For example, if it's a static build,
there's a good chance that it has been moved out of its installation directory.
That makes `nixBinDir` useless. Instead, we'll query the OS for the path to the
current executable, using `getSelfExe()`.
As a last resort, we resort to `PATH`. Hopefully we find a `nix` there that's compatible.
If you're porting Nix to a new platform, that might be good enough for a while, but
you'll want to improve `getSelfExe()` to work on your platform.
*/
std::string nixExePath = nixBinDir + "/nix";
if (!pathExists(nixExePath)) {
nixExePath = getSelfExe().value_or("nix");
}
buildHook = {
nixExePath,
"__build-remote",
};
}

void loadConfFile(AbstractConfig & config)
Expand Down
7 changes: 1 addition & 6 deletions src/libstore/globals.hh
Original file line number Diff line number Diff line change
Expand Up @@ -84,11 +84,6 @@ public:
*/
std::vector<Path> nixUserConfFiles;

/**
* The directory where the main programs are stored.
*/
Path nixBinDir;

/**
* The directory where the man pages are stored.
*/
Expand Down Expand Up @@ -246,7 +241,7 @@ public:
)",
{"build-timeout"}};

Setting<Strings> buildHook{this, {}, "build-hook",
Setting<Strings> buildHook{this, {"nix", "__build-remote"}, "build-hook",
R"(
The path to the helper program that executes remote builds.
Expand Down
1 change: 0 additions & 1 deletion src/libstore/local.mk
Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,6 @@ libstore_CXXFLAGS += \
-DNIX_STATE_DIR=\"$(NIX_ROOT)$(localstatedir)/nix\" \
-DNIX_LOG_DIR=\"$(NIX_ROOT)$(localstatedir)/log/nix\" \
-DNIX_CONF_DIR=\"$(NIX_ROOT)$(sysconfdir)/nix\" \
-DNIX_BIN_DIR=\"$(NIX_ROOT)$(bindir)\" \
-DNIX_MAN_DIR=\"$(NIX_ROOT)$(mandir)\" \
-DLSOF=\"$(NIX_ROOT)$(lsof)\"

Expand Down
2 changes: 0 additions & 2 deletions src/libstore/meson.build
Original file line number Diff line number Diff line change
Expand Up @@ -327,7 +327,6 @@ prefix = get_option('prefix')
path_opts = [
# Meson built-ins.
'datadir',
'bindir',
'mandir',
'libdir',
'includedir',
Expand Down Expand Up @@ -372,7 +371,6 @@ cpp_str_defines = {
'NIX_STATE_DIR': state_dir / 'nix',
'NIX_LOG_DIR': log_dir,
'NIX_CONF_DIR': sysconfdir / 'nix',
'NIX_BIN_DIR': bindir,
'NIX_MAN_DIR': mandir,
}

Expand Down
18 changes: 15 additions & 3 deletions src/libstore/unix/build/hook-instance.cc
Original file line number Diff line number Diff line change
Expand Up @@ -16,11 +16,23 @@ HookInstance::HookInstance()
if (buildHookArgs.empty())
throw Error("'build-hook' setting is empty");

auto buildHook = canonPath(buildHookArgs.front());
std::filesystem::path buildHook = buildHookArgs.front();
buildHookArgs.pop_front();

if (buildHook.is_absolute()) {
buildHook = std::filesystem::weakly_canonical(buildHook);
} else {
for (auto & dir : tokenizeString<Strings>(getEnv("PATH").value_or(""), ":")) {
auto resolved = dir / buildHook;
if (std::filesystem::exists(resolved)) {
buildHook = resolved;
break;
}
}
}

Strings args;
args.push_back(std::string(baseNameOf(buildHook)));
args.push_back(buildHook.filename().string());

for (auto & arg : buildHookArgs)
args.push_back(arg);
Expand Down Expand Up @@ -59,7 +71,7 @@ HookInstance::HookInstance()
if (dup2(builderOut.readSide.get(), 5) == -1)
throw SysError("dupping builder's stdout/stderr");

execv(buildHook.c_str(), stringsToCharPtrs(args).data());
execv(buildHook.native().c_str(), stringsToCharPtrs(args).data());

throw SysError("executing '%s'", buildHook);
});
Expand Down
11 changes: 6 additions & 5 deletions src/nix-channel/nix-channel.cc
Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@
#include "eval-settings.hh" // for defexpr
#include "users.hh"
#include "tarball.hh"
#include "bin-dir.hh"

#include <fcntl.h>
#include <regex>
Expand Down Expand Up @@ -67,7 +68,7 @@ static void removeChannel(const std::string & name)
channels.erase(name);
writeChannels();

runProgram(settings.nixBinDir + "/nix-env", true, { "--profile", profile, "--uninstall", name });
runProgram(getNixBin("nix-env").string(), true, { "--profile", profile, "--uninstall", name });
}

static Path nixDefExpr;
Expand Down Expand Up @@ -118,7 +119,7 @@ static void update(const StringSet & channelNames)

bool unpacked = false;
if (std::regex_search(filename, std::regex("\\.tar\\.(gz|bz2|xz)$"))) {
runProgram(settings.nixBinDir + "/nix-build", false, { "--no-out-link", "--expr", "import " + unpackChannelPath +
runProgram(getNixBin("nix-build").string(), false, { "--no-out-link", "--expr", "import " + unpackChannelPath +
"{ name = \"" + cname + "\"; channelName = \"" + name + "\"; src = builtins.storePath \"" + filename + "\"; }" });
unpacked = true;
}
Expand All @@ -143,7 +144,7 @@ static void update(const StringSet & channelNames)
for (auto & expr : exprs)
envArgs.push_back(std::move(expr));
envArgs.push_back("--quiet");
runProgram(settings.nixBinDir + "/nix-env", false, envArgs);
runProgram(getNixBin("nix-env").string(), false, envArgs);

// Make the channels appear in nix-env.
struct stat st;
Expand Down Expand Up @@ -244,7 +245,7 @@ static int main_nix_channel(int argc, char ** argv)
case cListGenerations:
if (!args.empty())
throw UsageError("'--list-generations' expects no arguments");
std::cout << runProgram(settings.nixBinDir + "/nix-env", false, {"--profile", profile, "--list-generations"}) << std::flush;
std::cout << runProgram(getNixBin("nix-env").string(), false, {"--profile", profile, "--list-generations"}) << std::flush;
break;
case cRollback:
if (args.size() > 1)
Expand All @@ -256,7 +257,7 @@ static int main_nix_channel(int argc, char ** argv)
} else {
envArgs.push_back("--rollback");
}
runProgram(settings.nixBinDir + "/nix-env", false, envArgs);
runProgram(getNixBin("nix-env").string(), false, envArgs);
break;
}

Expand Down
38 changes: 38 additions & 0 deletions src/nix/bin-dir.cc
Original file line number Diff line number Diff line change
@@ -0,0 +1,38 @@
#include "current-process.hh"
#include "file-system.hh"
#include "globals.hh"
#include "bin-dir.hh"

namespace nix {

namespace fs = std::filesystem;

fs::path getNixBin(std::optional<std::string_view> binaryNameOpt)
{
auto getBinaryName = [&] { return binaryNameOpt ? *binaryNameOpt : "nix"; };

// If the environment variable is set, use it unconditionally
if (auto envOpt = getEnvNonEmpty("NIX_BIN_DIR"))
return fs::path{*envOpt} / std::string{getBinaryName()};

// Use some-times avaiable OS tricks to get to the path of this Nix, and try that
if (auto selfOpt = getSelfExe()) {
fs::path path{*selfOpt};
if (binaryNameOpt)
path = path.parent_path() / std::string{*binaryNameOpt};
if (fs::exists(path))
return path;
}

// If `nix` exists at the hardcoded fallback path, use it.
{
auto path = fs::path{NIX_BIN_DIR} / std::string{getBinaryName()};
if (fs::exists(path))
return path;
}

// return just the name, hoping the exe is on the `PATH`
return getBinaryName();
}

}
31 changes: 31 additions & 0 deletions src/nix/bin-dir.hh
Original file line number Diff line number Diff line change
@@ -0,0 +1,31 @@
#pragma once
///@file

#include <filesystem>

namespace nix {

/**
* Get a path to the given Nix binary.
*
* Normally, nix is installed according to `NIX_BIN_DIR`, which is set
* at compile time, but can be overridden.
*
* However, it may not have been installed at all. For example, if it's
* a static build, there's a good chance that it has been moved out of
* its installation directory. That makes `NIX_BIN_DIR` useless.
* Instead, we'll query the OS for the path to the current executable,
* using `getSelfExe()`.
*
* As a last resort, we resort to `PATH`. Hopefully we find a `nix`
* there that's compatible. If you're porting Nix to a new platform,
* that might be good enough for a while, but you'll want to improve
* `getSelfExe()` to work on your platform.
*
* @param binary_name the exact binary name we're looking up. Might be
* `nix-*` instead of `nix` for the legacy CLI commands. Optional to use
* current binary name.
*/
std::filesystem::path getNixBin(std::optional<std::string_view> binary_name = {});

}
2 changes: 2 additions & 0 deletions src/nix/local.mk
Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,8 @@ endif

nix_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libstore) $(INCLUDE_libfetchers) $(INCLUDE_libexpr) $(INCLUDE_libflake) $(INCLUDE_libmain) -I src/libcmd -I doc/manual $(INCLUDE_nix)

nix_CXXFLAGS += -DNIX_BIN_DIR=\"$(NIX_ROOT)$(bindir)\"

nix_LIBS = libexpr libmain libfetchers libflake libstore libutil libcmd

nix_LDFLAGS = $(THREAD_LDFLAGS) $(SODIUM_LIBS) $(EDITLINE_LIBS) $(BOOST_LDFLAGS) $(LOWDOWN_LIBS)
Expand Down
12 changes: 12 additions & 0 deletions src/nix/main.cc
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@
#include "network-proxy.hh"
#include "eval-cache.hh"
#include "flake/flake.hh"
#include "bin-dir.hh"

#include <sys/types.h>
#include <regex>
Expand Down Expand Up @@ -366,6 +367,17 @@ void mainWrapped(int argc, char * * argv)
initGC();
flake::initLib(flakeSettings);

/* Set the build hook location
For builds we perform a self-invocation, so Nix has to be
self-aware. That is, it has to know where it is installed. We
don't think it's sentient.
*/
settings.buildHook.setDefault(Strings {
getNixBin({}),
"__build-remote",
});

#if __linux__
if (isRootUser()) {
try {
Expand Down
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