passing --stack to zig test makes the getrlimit/setrlimit test case fail

[andrewrk]

$ stage3/bin/zig test ../lib/std/std.zig --stack 16777216
Test [775/2593] test.getrlimit and setrlimit... FAIL (LimitTooBig)
/Users/andy/dev/zig/lib/std/os.zig:7130:19: 0x100e045b3 in setrlimit (test)
        .INVAL => return error.LimitTooBig, // this could also mean "invalid resource", but that would be unreachable
                  ^
/Users/andy/dev/zig/lib/std/os/test.zig:773:13: 0x100e03eb3 in test.getrlimit and setrlimit (test)
            try os.setrlimit(resource, limit);
            ^

zig/lib/std/os/test.zig

Lines 754 to 776 in b0dba46

	test "getrlimit and setrlimit" {
	if (!@hasDecl(os.system, "rlimit")) {
	return error.SkipZigTest;
	}
	inline for (std.meta.fields(os.rlimit_resource)) |field| {
	const resource = @as(os.rlimit_resource, @enumFromInt(field.value));
	const limit = try os.getrlimit(resource);
	// On 32 bit MIPS musl includes a fix which changes limits greater than -1UL/2 to RLIM_INFINITY.
	// See http://git.musl-libc.org/cgit/musl/commit/src/misc/getrlimit.c?id=8258014fd1e34e942a549c88c7e022a00445c352
	//
	// This happens for example if RLIMIT_MEMLOCK is bigger than ~2GiB.
	// In that case the following the limit would be RLIM_INFINITY and the following setrlimit fails with EPERM.
	if (comptime builtin.cpu.arch.isMIPS() and builtin.link_libc) {
	if (limit.cur != os.linux.RLIM.INFINITY) {
	try os.setrlimit(resource, limit);
	}
	} else {
	try os.setrlimit(resource, limit);
	}
	}
	}

It has something to do with these lines:

grep -RI stack_size_override ../src/link/MachO*
../src/link/MachO/zld.zig:    const stack_size = options.stack_size_override orelse 0;
../src/link/MachO/zld.zig:                    .stacksize = macho_file.base.options.stack_size_override orelse 0,
../src/link/MachO.zig:                .stacksize = self.base.options.stack_size_override orelse 0,

This is problematic because we want to be able to control the stack size from the compiler/linker. Relevant issues:

• Builtin function to tell you the maximum stack size of a given function #157
• safe recursion #1006
• eliminate stack overflow #1639

cc @kubkon

[nektro]

to me the trace makes it look like the error is from picking a number larger than ulimit -s, not intrinsic to passing --stack.

[mikdusan]

THIS. IS. APPLE. KERNEL.

        case RLIMIT_STACK:
                if (p->p_lflag & P_LCUSTOM_STACK) {
                        /* Process has a custom stack set - rlimit cannot be used to change it */
                        error = EINVAL;
                        goto out;
                }

source: https://github.com/apple-oss-distributions/xnu/blob/1031c584a5e37aff177559b9f69dbd3c8c3fd30a/bsd/kern/kern_resource.c#L1173-L1178

[andrewrk]

Nice, OK that's fine actually. We just need to not call setrlimit on the stack size in that std lib test.