Section and type conversion inside a function blows up section size

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
45/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp
Domain
compilers

Research direction

Start by running the provided main function with std::mem::create_section and compare its section size with the equivalent code at global scope. Trace how StringToByteConverter and converter.val affect the file section, then verify that the reproduced case reports a size of 0x2 rather than 0x40000002.

Written by the indexing model from the issue text.

Description

Given the following pattern:

import std.mem;

#pragma array_limit -1

union StringToByteConverter<auto size>
{
    u8 data[size];
    str val;
};

fn main()
{
    u128 size = 2;

    auto fileSection = std::mem::create_section("file");

    StringToByteConverter<size> converter @ 0x0 in fileSection;

    converter.val = "a" * size;
};

it would be expected for the "file" section to have a size of 0x2. Instead it has a size of 0x40000002.

Moving the code to global scope (so outside of main) resolves this issue.

Issue verified by AxCut on Discord.

Dominant language
C++
Stars
275
Forks
75
Avg merge
1d 22h
Merged PRs (30d)
10

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