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libutil: remove startProcess

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it's only used by runProgram2, and runProgram2 can do something much better.

Change-Id: Idba563e1adbe3fd8ce07a0bb8ad4fc1b0cc057b9
This commit is contained in:
eldritch horrors
2026-02-07 22:34:18 +01:00
parent 6063ffead9
commit b983c15336
3 changed files with 64 additions and 103 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lix/libstore/globals.cc
+17 -11
View File
@@ -261,17 +261,23 @@ StringSet Settings::getDefaultExtraPlatforms()
if (!null) {
throw Error("could not open /dev/null");
}
if (runProgram2(RunOptions{
.program = "arch",
.args = {"-arch", "x86_64", "/usr/bin/true"},
.redirections =
{{.dup = STDOUT_FILENO, .from = null.get()},
{.dup = STDERR_FILENO, .from = null.get()}}
}
).wait()
== 0)
{
extraPlatforms.insert("x86_64-darwin");
try {
if (runProgram2(
RunOptions{
.program = "/usr/bin/arch",
.searchPath = false,
.args = {"-arch", "x86_64", "/usr/bin/true"},
.redirections =
{{.dup = STDOUT_FILENO, .from = null.get()},
{.dup = STDERR_FILENO, .from = null.get()}}
}
).wait()
== 0)
{
extraPlatforms.insert("x86_64-darwin");
}
} catch (ExecError & e) {
debug("could not run /usr/bin/arch, not adding x86_64: %s", e.msg());
}
}
#endif
lix/libutil/processes.cc
+47 -75
View File
@@ -149,65 +149,6 @@ void killUser(uid_t uid)
//////////////////////////////////////////////////////////////////////
static pid_t doFork(std::function<void()> fun)
{
pid_t pid = fork();
if (pid != 0) return pid;
fun();
abort();
}
#if __linux__
static int childEntry(void * arg)
{
auto main = static_cast<std::function<void()> *>(arg);
(*main)();
return 1;
}
#endif
Pid startProcess(std::function<void()> fun, const ProcessOptions & options)
{
std::function<void()> wrapper = [&]() {
logger = makeSimpleLogger();
try {
fun();
} catch (std::exception & e) { // NOLINT(lix-foreign-exceptions)
try {
std::cerr << e.what() << "\n";
} catch (...) { }
} catch (...) { }
_exit(1);
};
pid_t pid = -1;
if (options.cloneFlags) {
#ifdef __linux__
// Not supported, since then we don't know when to free the stack.
assert(!(options.cloneFlags & CLONE_VM));
size_t stackSize = 1ul * 1024 * 1024;
auto stack = static_cast<char *>(mmap(0, stackSize,
PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, -1, 0));
if (stack == MAP_FAILED) throw SysError("allocating stack");
Finally freeStack([&]() { munmap(stack, stackSize); });
pid = clone(childEntry, stack + stackSize, options.cloneFlags | SIGCHLD, &wrapper);
#else
throw Error("clone flags are only supported on Linux");
#endif
} else
pid = doFork(wrapper);
if (pid == -1) throw SysError("unable to fork");
return Pid{pid};
}
kj::Promise<Result<std::string>>
runProgram(Path program, bool searchPath, const Strings args, bool isInteractive)
try {
@@ -352,8 +293,6 @@ RunningProgram runProgram2(const RunOptions & options)
Pipe out;
if (options.captureStdout) out.create();
ProcessOptions processOptions{};
printMsg(
lvlChatty,
"running command%s%s: %s %s%s",
@@ -364,9 +303,44 @@ RunningProgram runProgram2(const RunOptions & options)
concatMapStringsSep(" ", options.args, shellEscape)
);
Pipe info;
info.create();
/* Fork. */
Pid pid{startProcess(
[&]() {
Pid pid{fork()};
if (!pid) {
throw SysError("fork failed");
} else if (pid.get() > 0) {
info.writeSide.close();
auto status = readFile(info.readSide.get());
if (!status.empty()) {
auto result = pid.kill();
throw ExecError(result, "failed to run %s: %s", options.program, status);
} else {
return RunningProgram{
options.program,
std::move(pid),
options.captureStdout ? std::move(out.readSide) : AutoCloseFD{}
};
}
} else {
// nothing in the child may access global state like loggers, otherwise the
// child may deadlock if we forked while a lock was held by another thread.
// we cannot use writeFull because it might throw, we want to exit instead.
auto writeStatus = [&](std::string_view data) {
while (!data.empty()) {
const auto sent = ::write(info.writeSide.get(), data.data(), data.size());
if (sent < 0) {
_exit(255);
}
data.remove_prefix(sent);
}
};
try {
info.readSide.close();
if (options.environment) {
replaceEnv(*options.environment);
}
@@ -396,21 +370,19 @@ RunningProgram runProgram2(const RunOptions & options)
sys::execvp(options.program, args_);
// This allows you to refer to a program with a pathname relative
// to the PATH variable.
} else
} else {
sys::execv(options.program, args_);
}
throw SysError("executing '%1%'", options.program);
},
processOptions
)};
out.writeSide.close();
return RunningProgram{
options.program,
std::move(pid),
options.captureStdout ? std::move(out.readSide) : AutoCloseFD{}
};
} catch (std::exception & e) { // NOLINT(lix-foreign-exceptions)
writeStatus(e.what());
_exit(254);
} catch (...) {
writeStatus("unknown exception");
_exit(253);
}
}
}
RunningHelper runHelper(const char * name, RunOptions options)
lix/libutil/processes.hh
-17
View File
@@ -68,23 +68,6 @@ public:
*/
void killUser(uid_t uid);
/**
* Fork a process that runs the given function, and return the child
* pid to the caller.
*/
struct ProcessOptions
{
/**
* use clone() with the specified flags (Linux only)
*/
int cloneFlags = 0;
};
[[nodiscard]]
Pid startProcess(std::function<void()> fun, const ProcessOptions & options = ProcessOptions());
/**
* Run a program and return its stdout in a string (i.e., like the
* shell backtick operator).