std: stop exposing anything having to do with ucontext_t

This type is useful for two things:

* Doing non-local control flow with ucontext.h functions.
* Inspecting machine state in a signal handler.

The first use case is not one we support; we no longer expose bindings to those
functions in the standard library. They're also deprecated in POSIX and, as a
result, not available in musl.

The second use case is valid, but is very poorly served by the standard library.
As evidenced by my changes to std.debug.cpu_context.signal_context_t, users will
be better served rolling their own ucontext_t and especially mcontext_t types
which fit their specific situation. Further, these types tend to evolve
frequently as architectures evolve, and the standard library has not done a good
job keeping up, or even providing them for all supported targets.

Author: alexrp

lib/std/c.zig

@@ -1841,110 +1841,6 @@ pub const PROT = switch (native_os) {
     else => void,
 };
 
-pub const REG = switch (native_os) {
-    .linux => linux.REG,
-    .emscripten => emscripten.REG,
-    .freebsd => switch (builtin.cpu.arch) {
-        .aarch64 => struct {
-            pub const FP = 29;
-            pub const SP = 31;
-            pub const PC = 32;
-        },
-        .arm => struct {
-            pub const FP = 11;
-            pub const SP = 13;
-            pub const PC = 15;
-        },
-        .x86_64 => struct {
-            pub const RBP = 12;
-            pub const RIP = 21;
-            pub const RSP = 24;
-        },
-        else => struct {},
-    },
-    .solaris, .illumos => struct {
-        pub const R15 = 0;
-        pub const R14 = 1;
-        pub const R13 = 2;
-        pub const R12 = 3;
-        pub const R11 = 4;
-        pub const R10 = 5;
-        pub const R9 = 6;
-        pub const R8 = 7;
-        pub const RDI = 8;
-        pub const RSI = 9;
-        pub const RBP = 10;
-        pub const RBX = 11;
-        pub const RDX = 12;
-        pub const RCX = 13;
-        pub const RAX = 14;
-        pub const RIP = 17;
-        pub const RSP = 20;
-    },
-    .netbsd => switch (builtin.cpu.arch) {
-        .aarch64, .aarch64_be => struct {
-            pub const FP = 29;
-            pub const SP = 31;
-            pub const PC = 32;
-        },
-        .arm, .armeb => struct {
-            pub const FP = 11;
-            pub const SP = 13;
-            pub const PC = 15;
-        },
-        .x86 => struct {
-            pub const GS = 0;
-            pub const FS = 1;
-            pub const ES = 2;
-            pub const DS = 3;
-            pub const EDI = 4;
-            pub const ESI = 5;
-            pub const EBP = 6;
-            pub const ESP = 7;
-            pub const EBX = 8;
-            pub const EDX = 9;
-            pub const ECX = 10;
-            pub const EAX = 11;
-            pub const TRAPNO = 12;
-            pub const ERR = 13;
-            pub const EIP = 14;
-            pub const CS = 15;
-            pub const EFL = 16;
-            pub const UESP = 17;
-            pub const SS = 18;
-        },
-        .x86_64 => struct {
-            pub const RDI = 0;
-            pub const RSI = 1;
-            pub const RDX = 2;
-            pub const RCX = 3;
-            pub const R8 = 4;
-            pub const R9 = 5;
-            pub const R10 = 6;
-            pub const R11 = 7;
-            pub const R12 = 8;
-            pub const R13 = 9;
-            pub const R14 = 10;
-            pub const R15 = 11;
-            pub const RBP = 12;
-            pub const RBX = 13;
-            pub const RAX = 14;
-            pub const GS = 15;
-            pub const FS = 16;
-            pub const ES = 17;
-            pub const DS = 18;
-            pub const TRAPNO = 19;
-            pub const ERR = 20;
-            pub const RIP = 21;
-            pub const CS = 22;
-            pub const RFLAGS = 23;
-            pub const RSP = 24;
-            pub const SS = 25;
-        },
-        else => struct {},
-    },
-    else => struct {},
-};
 pub const RLIM = switch (native_os) {
     .linux => linux.RLIM,
     .emscripten => emscripten.RLIM,
@@ -4553,7 +4449,7 @@ pub const rusage = switch (native_os) {
 pub const siginfo_t = switch (native_os) {
     .linux => linux.siginfo_t,
     .emscripten => emscripten.siginfo_t,
-    .macos, .ios, .tvos, .watchos, .visionos => extern struct {
+    .driverkit, .macos, .ios, .tvos, .watchos, .visionos => extern struct {
         signo: c_int,
         errno: c_int,
         code: c_int,
@@ -11084,7 +10980,6 @@ pub const SETUSTACK = solaris.GETUSTACK;
 pub const SFD = solaris.SFD;
 pub const ctid_t = solaris.ctid_t;
 pub const file_obj = solaris.file_obj;
-pub const fpregset_t = solaris.fpregset_t;
 pub const id_t = solaris.id_t;
 pub const lif_ifinfo_req = solaris.lif_ifinfo_req;
 pub const lif_nd_req = solaris.lif_nd_req;

lib/std/c/solaris.zig

@@ -31,29 +31,6 @@ pub const poolid_t = id_t;
 pub const zoneid_t = id_t;
 pub const ctid_t = id_t;
 
-pub const fpregset_t = extern union {
-    regs: [130]u32,
-    chip_state: extern struct {
-        cw: u16,
-        sw: u16,
-        fctw: u8,
-        __fx_rsvd: u8,
-        fop: u16,
-        rip: u64,
-        rdp: u64,
-        mxcsr: u32,
-        mxcsr_mask: u32,
-        st: [8]extern union {
-            fpr_16: [5]u16,
-            __fpr_pad: u128,
-        },
-        xmm: [16]u128,
-        __fx_ign2: [6]u128,
-        status: u32,
-        xstatus: u32,
-    },
-};
-
 pub const GETCONTEXT = 0;
 pub const SETCONTEXT = 1;
 pub const GETUSTACK = 2;

lib/std/os/emscripten.zig

@@ -400,28 +400,6 @@ pub const timeval = extern struct {
     usec: i32,
 };
 
-pub const REG = struct {
-    pub const GS = 0;
-    pub const FS = 1;
-    pub const ES = 2;
-    pub const DS = 3;
-    pub const EDI = 4;
-    pub const ESI = 5;
-    pub const EBP = 6;
-    pub const ESP = 7;
-    pub const EBX = 8;
-    pub const EDX = 9;
-    pub const ECX = 10;
-    pub const EAX = 11;
-    pub const TRAPNO = 12;
-    pub const ERR = 13;
-    pub const EIP = 14;
-    pub const CS = 15;
-    pub const EFL = 16;
-    pub const UESP = 17;
-    pub const SS = 18;
-};
-
 pub const S = struct {
     pub const IFMT = 0o170000;
 
@@ -813,13 +791,6 @@ pub const dl_phdr_info = extern struct {
     phnum: u16,
 };
 
-pub const mcontext_t = extern struct {
-    gregs: [19]usize,
-    fpregs: [*]u8,
-    oldmask: usize,
-    cr2: usize,
-};
-
 pub const msghdr = std.c.msghdr;
 pub const msghdr_const = std.c.msghdr;
 
@@ -846,15 +817,6 @@ pub const timezone = extern struct {
     dsttime: i32,
 };
 
-pub const ucontext_t = extern struct {
-    flags: usize,
-    link: ?*ucontext_t,
-    stack: stack_t,
-    mcontext: mcontext_t,
-    sigmask: sigset_t,
-    regspace: [28]usize,
-};
-
 pub const utsname = extern struct {
     sysname: [64:0]u8,
     nodename: [64:0]u8,

lib/std/os/freebsd.zig

@@ -48,75 +48,3 @@ pub fn copy_file_range(fd_in: fd_t, off_in: ?*i64, fd_out: fd_t, off_out: ?*i64,
         else => |err| return unexpectedErrno(err),
     }
 }
-
-pub const ucontext_t = extern struct {
-    sigmask: std.c.sigset_t,
-    mcontext: mcontext_t,
-    link: ?*ucontext_t,
-    stack: std.c.stack_t,
-    flags: c_int,
-    __spare__: [4]c_int,
-    const mcontext_t = switch (builtin.cpu.arch) {
-        .x86_64 => extern struct {
-            onstack: u64,
-            rdi: u64,
-            rsi: u64,
-            rdx: u64,
-            rcx: u64,
-            r8: u64,
-            r9: u64,
-            rax: u64,
-            rbx: u64,
-            rbp: u64,
-            r10: u64,
-            r11: u64,
-            r12: u64,
-            r13: u64,
-            r14: u64,
-            r15: u64,
-            trapno: u32,
-            fs: u16,
-            gs: u16,
-            addr: u64,
-            flags: u32,
-            es: u16,
-            ds: u16,
-            err: u64,
-            rip: u64,
-            cs: u64,
-            rflags: u64,
-            rsp: u64,
-            ss: u64,
-            len: u64,
-            fpformat: u64,
-            ownedfp: u64,
-            fpstate: [64]u64 align(16),
-            fsbase: u64,
-            gsbase: u64,
-            xfpustate: u64,
-            xfpustate_len: u64,
-            spare: [4]u64,
-        },
-        .aarch64 => extern struct {
-            gpregs: extern struct {
-                x: [30]u64,
-                lr: u64,
-                sp: u64,
-                elr: u64,
-                spsr: u32,
-                _pad: u32,
-            },
-            fpregs: extern struct {
-                q: [32]u128,
-                sr: u32,
-                cr: u32,
-                flags: u32,
-                _pad: u32,
-            },
-            flags: u32,
-            _pad: u32,
-            _spare: [8]u64,
-        },
-        else => void,
-    };
-};

lib/std/os/linux.zig

@@ -47,9 +47,7 @@ const arch_bits = switch (native_arch) {
     .powerpc, .powerpcle => @import("linux/powerpc.zig"),
     .powerpc64, .powerpc64le => @import("linux/powerpc64.zig"),
     .s390x => @import("linux/s390x.zig"),
-    else => struct {
-        pub const ucontext_t = void;
-    },
+    else => struct {},
 };
 
 const syscall_bits = if (native_arch.isThumb()) @import("linux/thumb.zig") else arch_bits;
@@ -94,22 +92,19 @@ pub const Elf_Symndx = arch_bits.Elf_Symndx;
 pub const F = arch_bits.F;
 pub const Flock = arch_bits.Flock;
 pub const HWCAP = arch_bits.HWCAP;
-pub const REG = arch_bits.REG;
 pub const SC = arch_bits.SC;
 pub const Stat = arch_bits.Stat;
 pub const VDSO = arch_bits.VDSO;
 pub const blkcnt_t = arch_bits.blkcnt_t;
 pub const blksize_t = arch_bits.blksize_t;
 pub const dev_t = arch_bits.dev_t;
 pub const ino_t = arch_bits.ino_t;
-pub const mcontext_t = arch_bits.mcontext_t;
 pub const mode_t = arch_bits.mode_t;
 pub const nlink_t = arch_bits.nlink_t;
 pub const off_t = arch_bits.off_t;
 pub const time_t = arch_bits.time_t;
 pub const timeval = arch_bits.timeval;
 pub const timezone = arch_bits.timezone;
-pub const ucontext_t = arch_bits.ucontext_t;
 pub const user_desc = arch_bits.user_desc;
 
 pub const tls = @import("linux/tls.zig");

lib/std/os/linux/aarch64.zig

@@ -241,23 +241,4 @@ pub const timezone = extern struct {
     dsttime: i32,
 };
 
-pub const mcontext_t = extern struct {
-    fault_address: usize,
-    regs: [31]usize,
-    sp: usize,
-    pc: usize,
-    pstate: usize,
-    // Make sure the field is correctly aligned since this area
-    // holds various FP/vector registers
-    reserved1: [256 * 16]u8 align(16),
-};
-
-pub const ucontext_t = extern struct {
-    flags: usize,
-    link: ?*ucontext_t,
-    stack: stack_t,
-    sigmask: [1024 / @bitSizeOf(c_ulong)]c_ulong, // Currently a libc-compatible (1024-bit) sigmask
-    mcontext: mcontext_t,
-};
-
 pub const Elf_Symndx = u32;

lib/std/os/linux/arm.zig

@@ -277,37 +277,4 @@ pub const timezone = extern struct {
     dsttime: i32,
 };
 
-pub const mcontext_t = extern struct {
-    trap_no: usize,
-    error_code: usize,
-    oldmask: usize,
-    arm_r0: usize,
-    arm_r1: usize,
-    arm_r2: usize,
-    arm_r3: usize,
-    arm_r4: usize,
-    arm_r5: usize,
-    arm_r6: usize,
-    arm_r7: usize,
-    arm_r8: usize,
-    arm_r9: usize,
-    arm_r10: usize,
-    arm_fp: usize,
-    arm_ip: usize,
-    arm_sp: usize,
-    arm_lr: usize,
-    arm_pc: usize,
-    arm_cpsr: usize,
-    fault_address: usize,
-};
-
-pub const ucontext_t = extern struct {
-    flags: usize,
-    link: ?*ucontext_t,
-    stack: stack_t,
-    mcontext: mcontext_t,
-    sigmask: [1024 / @bitSizeOf(c_ulong)]c_ulong, // Currently a libc-compatible (1024-bit) sigmask
-    regspace: [64]u64,
-};
-
 pub const Elf_Symndx = u32;