Modifying variable through pointer to "anonymous value" crashes program

[oskarnp]

The following code causes program to crash with Segmentation fault on Windows using master (f7721ac). On 0.4.0 program silently crashes without any trace.
No warnings or errors are generated.

const debug = @import("std").debug;

const Foo = struct {
    bla: i32,
};

fn do_this(f: *Foo) void {
    f.bla = 123;
    debug.warn("f = {}\n", f.bla);
}

pub fn main() void {
    do_this(&Foo{ .bla = 3 });
}

My assumption would be that &Foo{.bla = 3} would behave like a compound literal in C99; that is an lvalue with storage duration of enclosing block scope, just like if I had assigned it to a temporary variable.

[andrewrk]

Thanks for taking the time to file an issue.

This is a missing compile error - Foo{ .bla = 3 } is a constant; generated in the constant data section. The reference to it is incorrectly mutable. The segfault is coming from writing to constant data section which does not have write perms.

[Vexu]

Duplicate of #2130, fixed by #4971.

./build/a.zig:285:17: error: expected type '*Foo', found '*const Foo'
    do_this(&Foo{ .bla = 3 });
                ^
./build/a.zig:285:17: note: cast discards const qualifier
    do_this(&Foo{ .bla = 3 });
                ^