Commit 3f956f98903214a6a79a123d62c4084ea3ba49f9 | zig

author	Alex Rønne Petersen <alex@alexrp.com> 2026-06-17 07:18:25+02:00
committer	Alex Rønne Petersen <alex@alexrp.com> 2026-06-17 07:22:07+02:00
log	3f956f98903214a6a79a123d62c4084ea3ba49f9
tree	84639c6497a69dd67debd86e4f63e60e4b02b7a1
parent	e74fd3ce555c675235fa65fa3647caeb4757b4cd
signature	Signed by SSH key SHA256:7B/LJ7bpR1eX8aCXSr4mtd5M45VMPKcx9zY8e95b5QM

std.os.linux: fix lseek() for x32/n32

This is the one syscall that returns a u64 despite usize == u32 in these ABIs.
Rather than huge API churn for all return types in std.os.linux just to benefit
these incredibly niche ABIs, just special-case this particular syscall, as we do
with a few others depending on arch.

3 files changed, 44 insertions(+), 3 deletions(-)

lib
- std
  - os
    linux.zig
    linux
    mipsn32.zig
    x32.zig

lib/std/os/linux.zig+11-3

 @@ -80,6 +80,7 @@ pub const restore_rt = syscall_bits.restore_rt;
 pub const socketcall = syscall_bits.socketcall;
 pub const syscall_pipe = syscall_bits.syscall_pipe;
 pub const syscall_fork = syscall_bits.syscall_fork;
+pub const syscall_lseek = syscall_bits.syscall_lseek;
 pub fn clone(
     func: *const fn (arg: usize) callconv(.c) u8,
 @@ -1809,7 +1810,7 @@ pub fn fchmodat2(fd: fd_t, path: [*:0]const u8, mode: mode_t, flags: u32) usize
 }
 /// Can only be called on 32 bit systems. For 64 bit see `lseek`.
-pub fn llseek(fd: fd_t, offset: off_t, result: ?*off_t, whence: u32) usize {
+pub fn llseek(fd: fd_t, offset: off_t, result: ?*off_t, whence: u32) u32 {
     // NOTE: The offset parameter splitting is independent from the target
     // endianness.
     return syscall5(
 @@ -1823,8 +1824,15 @@ pub fn llseek(fd: fd_t, offset: off_t, result: ?*off_t, whence: u32) usize {
 }
 /// Can only be called on 64 bit systems. For 32 bit see `llseek`.
-pub fn lseek(fd: fd_t, offset: off_t, whence: u32) usize {
+pub fn lseek(fd: fd_t, offset: off_t, whence: u32) u64 {
-    return syscall3(.lseek, @as(u32, @bitCast(fd)), @as(u64, @bitCast(offset)), whence);
+    return switch (builtin.abi) {
+        .gnuabin32,
+        .muslabin32,
+        .gnux32,
+        .muslx32,
+        => syscall_lseek(fd, offset, whence),
+        else => syscall3(.lseek, @as(u32, @bitCast(fd)), @as(u64, @bitCast(offset)), whence),
+    };
 }
 pub fn exit(status: i32) noreturn {

lib/std/os/linux/mipsn32.zig+19

...	@@ -163,6 +163,25 @@ pub fn syscall_pipe(	...	@@ -163,6 +163,25 @@ pub fn syscall_pipe(
163	: .{ .r1 = true, .r3 = true, .r5 = true, .r6 = true, .r7 = true, .r8 = true, .r9 = true, .r10 = true, .r11 = true, .r12 = true, .r13 = true, .r14 = true, .r15 = true, .r24 = true, .r25 = true, .hi = true, .lo = true, .memory = true });	163	: .{ .r1 = true, .r3 = true, .r5 = true, .r6 = true, .r7 = true, .r8 = true, .r9 = true, .r10 = true, .r11 = true, .r12 = true, .r13 = true, .r14 = true, .r15 = true, .r24 = true, .r25 = true, .hi = true, .lo = true, .memory = true });
164	}	164	}
165		165
		166	pub fn syscall_lseek(
		167	fd: std.os.linux.fd_t,
		168	offset: std.os.linux.off_t,
		169	whence: u32,
		170	) u64 {
		171	return asm volatile (
		172	\\ syscall
		173	\\ beq $a3, $zero, 1f
		174	\\ blez $v0, 1f
		175	\\ dsubu $v0, $zero, $v0
		176	\\1:
		177	: [ret] "={$2}" (-> u64),
		178	: [number] "{$2}" (@intFromEnum(SYS.lseek)),
		179	[fd] "{$4}" (@as(u32, @bitCast(fd))),
		180	[offset] "{$5}" (@as(u64, @bitCast(offset))),
		181	[whence] "{$6}" (whence),
		182	: .{ .r1 = true, .r3 = true, .r7 = true, .r8 = true, .r9 = true, .r10 = true, .r11 = true, .r12 = true, .r13 = true, .r14 = true, .r15 = true, .r24 = true, .r25 = true, .hi = true, .lo = true, .memory = true });
		183	}
		184
166	pub fn clone() callconv(.naked) u32 {	185	pub fn clone() callconv(.naked) u32 {
167	// __clone(func, stack, flags, arg, ptid, tls, ctid)	186	// __clone(func, stack, flags, arg, ptid, tls, ctid)
168	// a0, a1, a2, a3, a4, a5, a6	187	// a0, a1, a2, a3, a4, a5, a6

lib/std/os/linux/x32.zig+14

...	@@ -109,6 +109,20 @@ pub fn syscall6(	...	@@ -109,6 +109,20 @@ pub fn syscall6(
109	: .{ .rcx = true, .r11 = true, .memory = true });	109	: .{ .rcx = true, .r11 = true, .memory = true });
110	}	110	}
111		111
		112	pub fn syscall_lseek(
		113	fd: std.os.linux.fd_t,
		114	offset: std.os.linux.off_t,
		115	whence: u32,
		116	) u64 {
		117	return asm volatile ("syscall"
		118	: [ret] "={rax}" (-> u64),
		119	: [number] "{rax}" (@intFromEnum(SYS.lseek)),
		120	[fd] "{rdi}" (@as(u32, @bitCast(fd))),
		121	[offset] "{rsi}" (@as(u64, @bitCast(offset))),
		122	[whence] "{rdx}" (whence),
		123	: .{ .rcx = true, .r11 = true, .memory = true });
		124	}
		125
112	pub fn clone() callconv(.naked) u32 {	126	pub fn clone() callconv(.naked) u32 {
113	asm volatile (	127	asm volatile (
114	\\ movl $0x40000038,%%eax // SYS_clone	128	\\ movl $0x40000038,%%eax // SYS_clone