Compile crash

[crat1985]

Zig Version

0.14.0-dev.1200+104553714

Steps to Reproduce and Observed Behavior

Create a new Zig project directory, and replace the main file content with the following :

const std = @import("std");

pub const StackAllocator = struct {
    data: [40]u8 = undefined,
    offset: usize = 0,

    const Self = @This();

    fn alloc(ctx: *anyopaque, n: usize, ptr_align: u8, return_address: usize) ?[*]u8 {
        const self: *Self = @ptrCast(@alignCast(ctx));
        // _ = n;
        // _ = self;

        _ = ptr_align;
        _ = return_address;

        const data = self.data[self.offset .. self.offset + n];

        return data.ptr + n;
        // return null;
    }

    pub fn allocator(comptime self: *Self) std.mem.Allocator {
        return std.mem.Allocator{ .ptr = self, .vtable = &.{ .alloc = alloc, .free = undefined, .resize = undefined } };
    }
};

pub const HandlerFn =
    *const fn () void;

pub fn main() !void {
    comptime {
        var stack_allocator = StackAllocator{};

        const allocator = stack_allocator.allocator();

        const value =
            try allocator.create(HandlerFn);

        const handle_fn = struct {
            fn handle() void {}
        }.handle;

        value.* = handle_fn;
    }
}

Run zig build

Expected Behavior

The code to compile or at least to throw a real error (I think the issue comes from setting the std.mem.Allocator VTable's functions to undefined).
When compiling, I get the following error :

install
└─ install zig-tiny-http
   └─ zig build-exe zig-tiny-http Debug native failure
error: the following command terminated unexpectedly:
/usr/local/bin/zig build-exe -ODebug -Mroot=/home/riccardo/tiny-http-zig-reduced/src/main.zig --cache-dir /home/riccardo/tiny-http-zig-reduced/.zig-cache --global-cache-dir /home/riccardo/.cache/zig --name zig-tiny-http --zig-lib-dir /usr/local/bin/lib/ --listen=- 
Build Summary: 0/3 steps succeeded; 1 failed
install transitive failure
└─ install zig-tiny-http transitive failure
   └─ zig build-exe zig-tiny-http Debug native failure
error: the following build command failed with exit code 1:
/home/riccardo/tiny-http-zig-reduced/.zig-cache/o/1b6808dabce3e4d55c3311488c60b910/build /usr/local/bin/zig /usr/local/bin/lib /home/riccardo/tiny-http-zig-reduced /home/riccardo/tiny-http-zig-reduced/.zig-cache /home/riccardo/.cache/zig --seed 0x42d96380 -Z957a6ec646f3fd6e

[crat1985]

When using this code :

const std = @import("std");

pub const StackAllocator = struct {
    data: [40]u8 = undefined,
    offset: usize = 0,

    const Self = @This();

    fn alloc(ctx: *anyopaque, n: usize, ptr_align: u8, return_address: usize) ?[*]u8 {
        const self: *Self = @ptrCast(@alignCast(ctx));
        _ = n;
        _ = self;

        _ = ptr_align;
        _ = return_address;

        // const data = self.data[self.offset .. self.offset + n];

        // return data.ptr + n;
        return null;
    }

    pub fn allocator(comptime self: *Self) std.mem.Allocator {
        return std.mem.Allocator{ .ptr = self, .vtable = &.{ .alloc = alloc, .free = undefined, .resize = undefined } };
    }
};

pub const HandlerFn =
    *const fn () void;

pub fn main() !void {
    comptime {
        var stack_allocator = StackAllocator{};

        const allocator = stack_allocator.allocator();

        const value =
            try allocator.create(HandlerFn);

        const handle_fn = struct {
            fn handle() void {}
        }.handle;

        value.* = handle_fn;
    }
}

The diff is :

     fn alloc(ctx: *anyopaque, n: usize, ptr_align: u8, return_address: usize) ?[*]u8 {
         const self: *Self = @ptrCast(@alignCast(ctx));
-        // _ = n;
-        // _ = self;
+        _ = n;
+        _ = self;
 
         _ = ptr_align;
         _ = return_address;
 
-        const data = self.data[self.offset .. self.offset + n];
+        // const data = self.data[self.offset .. self.offset + n];
 
-        return data.ptr + n;
-        // return null;
+        // return data.ptr + n;
+        return null;
     }
 
     pub fn allocator(comptime self: *Self) std.mem.Allocator {

There is a compiler error :

install
└─ install zig-tiny-http
   └─ zig build-exe zig-tiny-http Debug native 1 errors
src/main.zig:38:13: error: function called at runtime cannot return value at comptime
            try allocator.create(HandlerFn);
            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
referenced by:
    posixCallMainAndExit: /usr/local/bin/lib/std/start.zig:614:37
    _start: /usr/local/bin/lib/std/start.zig:421:40
    3 reference(s) hidden; use '-freference-trace=5' to see all references
error: the following command failed with 1 compilation errors:
/usr/local/bin/zig build-exe -ODebug -Mroot=/home/riccardo/tiny-http-zig-reduced/src/main.zig --cache-dir /home/riccardo/tiny-http-zig-reduced/.zig-cache --global-cache-dir /home/riccardo/.cache/zig --name zig-tiny-http --zig-lib-dir /usr/local/bin/lib/ --listen=- 
Build Summary: 0/3 steps succeeded; 1 failed
install transitive failure
└─ install zig-tiny-http transitive failure
   └─ zig build-exe zig-tiny-http Debug native 1 errors
error: the following build command failed with exit code 1:
/home/riccardo/tiny-http-zig-reduced/.zig-cache/o/1b6808dabce3e4d55c3311488c60b910/build /usr/local/bin/zig /usr/local/bin/lib /home/riccardo/tiny-http-zig-reduced /home/riccardo/tiny-http-zig-reduced/.zig-cache /home/riccardo/.cache/zig --seed 0x8c540e68 -Za55a3e4c4a160d32

[Vexu]

Duplicate of #20765