Segmentation Fault from GeneralPurposeAllocator

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1

Hi,

I am not able to understand why this piece of code is causing segmentation fault. Looking for an explanation.

const std = @import("std");

const Table = struct {
    pages: [100]?*Page,
};

const Page = struct {
    page: [12]*Row,
};

const Row = struct {
    id: i32,
    username: [32]u8,
    email: [255]u8,
};

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    const table = try allocator.create(Table);

    for (0..100) |i| {
        table.*.pages[i] = null;
    }

    std.debug.print("table.*.pages[0]: {any}.\n", .{table.*.pages[0]});
    const allocated_page = try allocator.create(Page);
    std.debug.print("allocated_page: {any}.\n", .{allocated_page});
    table.*.pages[0] = allocated_page;
}

Output:

zig run demo.zig
table.*.pages[0]: null.
allocated_page: demo.Page{ .page = { demo.Row{ .id = Segmentation fault at address 0xaaaaaaaaaaaaaaaa
Panicked during a panic. Aborting.
zsh: abort      zig run demo.zig

zig version: 0.13.0

2

The print function is following the pointers in Page, but they are unitialized.

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