Commit 6eb5e56306620e72ae80d7ad6626f8d0ceb24af5 | zig

author	Pat Tullmann <pat.github@tullmann.org> 2025-04-28 21:03:23-07:00
committer	Alex Rønne Petersen <alex@alexrp.com> 2025-05-09 15:10:25+02:00
log	6eb5e56306620e72ae80d7ad6626f8d0ceb24af5
tree	2ca4383369165a41814d3b95f148e86f46627920
parent	85a6b75e18248bad83437323cab14fe1973057ec

std.posix: Add sigrtmin() and sigrtmax()

For C code the macros SIGRTMIN and SIGRTMAX provide these values.  In
practice what looks like a constant is actually provided by a libc call.
So the Zig implementations are explicitly function calls.

glibc (and Musl) export a run-time minimum "real-time" signal number,
based on how many signals are reserved for internal implementation details
(generally threading).  In practice, on Linux, sigrtmin() is 35 on glibc
with the older LinuxThread and 34 with the newer NPTL-based
implementation.  Musl always returns 35.  The maximum "real-time" signal
number is NSIG - 1 (64 on most Linux kernels, but 128 on MIPS).

When not linking a C Library, Zig can report the full range of "rt"
signals (none are reserved by Zig).

Fixes #21189

4 files changed, 44 insertions(+), 2 deletions(-)

lib
- std
  - c.zig
  - os
    linux.zig
  - posix.zig
  - posix
    test.zig

lib/std/c.zig+13

...	@@ -10347,6 +10347,16 @@ pub const sigaction = switch (native_os) {	...	@@ -10347,6 +10347,16 @@ pub const sigaction = switch (native_os) {
10347	else => private.sigaction,	10347	else => private.sigaction,
10348	};	10348	};
10349		10349
		10350	/// Zig's version of SIGRTMIN. Actually a function.
		10351	pub fn sigrtmin() u8 {
		10352	return @truncate(@as(c_uint, @bitCast(private.__libc_current_sigrtmin())));
		10353	}
		10354
		10355	/// Zig's version of SIGRTMAX. Actually a function.
		10356	pub fn sigrtmax() u8 {
		10357	return @truncate(@as(c_uint, @bitCast(private.__libc_current_sigrtmax())));
		10358	}
		10359
10350	pub const sigfillset = switch (native_os) {	10360	pub const sigfillset = switch (native_os) {
10351	.netbsd => private.__sigfillset14,	10361	.netbsd => private.__sigfillset14,
10352	else => private.sigfillset,	10362	else => private.sigfillset,
...	@@ -11213,6 +11223,9 @@ const private = struct {	...	@@ -11213,6 +11223,9 @@ const private = struct {
11213	extern "c" fn __getdents30(fd: c_int, buf_ptr: [*]u8, nbytes: usize) c_int;	11223	extern "c" fn __getdents30(fd: c_int, buf_ptr: [*]u8, nbytes: usize) c_int;
11214	extern "c" fn __sigaltstack14(ss: ?stack_t, old_ss: ?stack_t) c_int;	11224	extern "c" fn __sigaltstack14(ss: ?stack_t, old_ss: ?stack_t) c_int;
11215		11225
		11226	extern "c" fn __libc_current_sigrtmin() c_int;
		11227	extern "c" fn __libc_current_sigrtmax() c_int;
		11228
11216	// Don't forget to add another clown when an OS picks yet another unique	11229	// Don't forget to add another clown when an OS picks yet another unique
11217	// symbol name for errno location!	11230	// symbol name for errno location!
11218	// 🤡🤡🤡🤡🤡🤡	11231	// 🤡🤡🤡🤡🤡🤡

lib/std/os/linux.zig+13

...	@@ -1801,6 +1801,19 @@ const SigsetElement = c_ulong;	...	@@ -1801,6 +1801,19 @@ const SigsetElement = c_ulong;
1801		1801
1802	const sigset_len = @typeInfo(sigset_t).array.len;	1802	const sigset_len = @typeInfo(sigset_t).array.len;
1803		1803
		1804	/// Zig's SIGRTMIN, but is a function for compatibility with glibc
		1805	pub fn sigrtmin() u8 {
		1806	// Default is 32 in the kernel UAPI: https://github.com/torvalds/linux/blob/78109c591b806e41987e0b83390e61d675d1f724/include/uapi/asm-generic/signal.h#L50
		1807	// AFAICT, all architectures that override this also set it to 32:
		1808	// https://github.com/search?q=repo%3Atorvalds%2Flinux+sigrtmin+path%3Auapi&type=code
		1809	return 32;
		1810	}
		1811
		1812	/// Zig's SIGRTMAX, but is a function for compatibility with glibc
		1813	pub fn sigrtmax() u8 {
		1814	return NSIG - 1;
		1815	}
		1816
1804	/// Zig's version of sigemptyset. Returns initialized sigset_t.	1817	/// Zig's version of sigemptyset. Returns initialized sigset_t.
1805	pub fn sigemptyset() sigset_t {	1818	pub fn sigemptyset() sigset_t {
1806	return [_]SigsetElement{0} ** sigset_len;	1819	return [_]SigsetElement{0} ** sigset_len;

lib/std/posix.zig+2

...	@@ -151,6 +151,8 @@ pub const rusage = system.rusage;	...	@@ -151,6 +151,8 @@ pub const rusage = system.rusage;
151	pub const sa_family_t = system.sa_family_t;	151	pub const sa_family_t = system.sa_family_t;
152	pub const siginfo_t = system.siginfo_t;	152	pub const siginfo_t = system.siginfo_t;
153	pub const sigset_t = system.sigset_t;	153	pub const sigset_t = system.sigset_t;
		154	pub const sigrtmin = system.sigrtmin;
		155	pub const sigrtmax = system.sigrtmax;
154	pub const sockaddr = system.sockaddr;	156	pub const sockaddr = system.sockaddr;
155	pub const socklen_t = system.socklen_t;	157	pub const socklen_t = system.socklen_t;
156	pub const stack_t = system.stack_t;	158	pub const stack_t = system.stack_t;

lib/std/posix/test.zig+16-2

 @@ -859,6 +859,17 @@ test "shutdown socket" {
     std.net.Stream.close(.{ .handle = sock });
 }
+test "sigrtmin/max" {
+    if (native_os == .wasi or native_os == .windows or native_os == .macos) {
+        return error.SkipZigTest;
+    }
+    try std.testing.expect(posix.sigrtmin() >= 32);
+    try std.testing.expect(posix.sigrtmin() >= posix.system.sigrtmin());
+    try std.testing.expect(posix.sigrtmin() < posix.system.sigrtmax());
+    try std.testing.expect(posix.sigrtmax() < posix.NSIG);
+}
 test "sigset empty/full" {
     if (native_os == .wasi or native_os == .windows)
         return error.SkipZigTest;
 @@ -875,10 +886,13 @@ test "sigset empty/full" {
     try expectEqual(true, posix.sigismember(&set, @truncate(posix.SIG.INT)));
 }
-// Some signals (32 - 34 on glibc/musl) are not allowed to be added to a
+// Some signals (i.e., 32 - 34 on glibc/musl) are not allowed to be added to a
 // sigset by the C library, so avoid testing them.
 fn reserved_signo(i: usize) bool {
-    return builtin.link_libc and (i >= 32 and i <= 34);
+    if (native_os == .macos) {
+        return false;
+    }
+    return builtin.link_libc and (i >= 32 and i < posix.sigrtmin());
 }
 test "sigset add/del" {