Trying to build @memset with a slice pointer causes segfault

[pprettysimpple]

Zig Version

0.11.0-dev.3395+1e7dcaa3a

Steps to Reproduce and Observed Behavior

1. Write to demo.zig:

pub fn main() void {
    var slice: []u8 = undefined;
    @memset(slice.ptr, 0);
}

2. Run zig build-exe demo.zig Output: Segmentation fault (core dumped)

Expected Behavior

Expected some error message

[travisstaloch]

~~this is not a bug. the crash happens because. the slice is undefined. this is an issue tracker, not a place to ask questions. these types of questions should be directed to the community: https://github.com/ziglang/zig/wiki/Community~~

[nektro]

thread 875350 panic: reached unreachable code
/home/meghan/src/zig/src/codegen/llvm.zig:8327:56: 0x15f108f in airMemset (zig)
                const len = self.sliceOrArrayLenInBytes(dest_slice, ptr_ty);
                                                       ^
/home/meghan/src/zig/src/codegen/llvm.zig:4466:54: 0x1107b1a in genBody (zig)
                .memset_safe    => try self.airMemset(inst, true),
                                                     ^
/home/meghan/src/zig/src/codegen/llvm.zig:1215:19: 0x1101e2b in updateFunc (zig)
        fg.genBody(air.getMainBody()) catch |err| switch (err) {
                  ^
/home/meghan/src/zig/src/link/Elf.zig:2582:74: 0x110a7bb in updateFunc (zig)
        if (self.llvm_object) |llvm_object| return llvm_object.updateFunc(mod, func_index, air, liveness);
                                                                         ^
/home/meghan/src/zig/src/link.zig:572:77: 0xec5833 in updateFunc (zig)
            .elf   => return @fieldParentPtr(Elf,   "base", base).updateFunc(module, func_index, air, liveness),
                                                                            ^
/home/meghan/src/zig/src/Module.zig:4215:37: 0xd0485a in ensureFuncBodyAnalyzed (zig)
            comp.bin_file.updateFunc(mod, func_index, air, liveness) catch |err| switch (err) {
                                    ^
/home/meghan/src/zig/src/Compilation.zig:3143:42: 0xd01e39 in processOneJob (zig)
            module.ensureFuncBodyAnalyzed(func) catch |err| switch (err) {
                                         ^
/home/meghan/src/zig/src/Compilation.zig:3080:30: 0xba0f9e in performAllTheWork (zig)
            try processOneJob(comp, work_item, main_progress_node);
                             ^
/home/meghan/src/zig/src/Compilation.zig:2029:31: 0xb9d648 in update (zig)
    try comp.performAllTheWork(main_progress_node);
                              ^
/home/meghan/src/zig/src/main.zig:3840:24: 0xbcad3a in updateModule (zig)
        try comp.update(main_progress_node);
                       ^
/home/meghan/src/zig/src/main.zig:3275:17: 0xa54aff in buildOutputType (zig)
    updateModule(comp) catch |err| switch (err) {
                ^
/home/meghan/src/zig/src/main.zig:277:31: 0xa07a65 in mainArgs (zig)
        return buildOutputType(gpa, arena, args, .run);
                              ^
/home/meghan/src/zig/src/main.zig:213:20: 0xa04c05 in main (zig)
    return mainArgs(gpa, arena, args);
                   ^
/home/meghan/src/zig/lib/std/start.zig:609:37: 0xa04688 in main (zig)
            const result = root.main() catch |err| {
                                    ^
???:?:?: 0x7f9fb52bc24d in ??? (???)
???:?:?: 0x7ffcf8e47cc4 in ??? (???)
Aborted (core dumped)

[travisstaloch]

this is not a bug. the crash happens because. the slice is undefined. this is an issue tracker, not a place to ask questions. these types of questions should be directed to the community: https://github.com/ziglang/zig/wiki/Community

I think I responded too quickly. This does seem like a bug. I agree that it shouldn't crash the compiler. I originally thought this was a runtime crash due to dereffing slice.ptr.

[Vexu]

#16698 was a duplicate of this.