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No error on comptime expression loading runtime value #22296

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kj4tmp opened this issue Dec 23, 2024 · 1 comment · May be fixed by #22305
Closed

No error on comptime expression loading runtime value #22296

kj4tmp opened this issue Dec 23, 2024 · 1 comment · May be fixed by #22305
Labels
bug Observed behavior contradicts documented or intended behavior frontend Tokenization, parsing, AstGen, Sema, and Liveness.
Milestone
0.14.0

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@kj4tmp
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kj4tmp commented Dec 23, 2024

Zig Version

0.14.0-dev.2540+f857bf72e

Steps to Reproduce and Observed Behavior

Create file test.zig with the following contents:

const std = @import("std");

test {
    var value = @as(u5, 0);
    const Foo = packed struct(u7) {
        val2: u7,
    };
    const foo: Foo = .{ .val2 = value };
    // if `comptime` is removed here, the segfault goes away
    std.debug.print("{}", .{comptime foo});
}

Observe segfault:

$ zig test test.zig 
Segmentation fault

Expected Behavior

Not sure, when I remove the comptime I get the following output:

test.zig:4:9: error: local variable is never mutated
    var value = @as(u5, 0);
        ^~~~~
test.zig:4:9: note: consider using 'const'
@kj4tmp kj4tmp added the bug Observed behavior contradicts documented or intended behavior label Dec 23, 2024
@Vexu
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Vexu commented Dec 23, 2024

That error is correct but if you suppress it with _ = &value there should be an unable to evaluate comptime expression error.

Stack trace 

thread 374045 panic: reached unreachable code
/home/vexu/.config/Code - OSS/User/globalStorage/ziglang.vscode-zig/zig/linux-x86_64-0.14.0-dev.2547+77c63ac36/lib/std/debug.zig:405:14: 0xa41c14c in assert (zig)
    if (!ok) unreachable; // assertion failure
             ^
/home/vexu/Documents/zig/zig/src/Liveness.zig:174:15: 0xb66c7ce in analyze (zig)
        assert(data.live_set.count() == 0);
              ^
/home/vexu/Documents/zig/zig/src/Zcu/PerThread.zig:907:40: 0xb26a4e7 in linkerUpdateFunc (zig)
    var liveness = try Liveness.analyze(gpa, air, ip);
                                       ^
/home/vexu/Documents/zig/zig/src/link.zig:1548:32: 0xae68ac1 in doTask (zig)
            pt.linkerUpdateFunc(func.func, func.air) catch |err| switch (err) {
                               ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:3900:20: 0xaab2ec8 in dispatchCodegenTask (zig)
        link.doTask(comp, tid, link_task);
                   ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:3677:37: 0xa8433a7 in processOneJob (zig)
            comp.dispatchCodegenTask(tid, .{ .codegen_func = func });
                                    ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:3634:30: 0xa65fe92 in performAllTheWorkInner (zig)
            try processOneJob(@intFromEnum(Zcu.PerThread.Id.main), comp, job, main_progress_node);
                             ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:3494:36: 0xa4f4cec in performAllTheWork (zig)
    try comp.performAllTheWorkInner(main_progress_node);
                                   ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:2251:31: 0xa4ed1d6 in update (zig)
    try comp.performAllTheWork(main_progress_node);
                              ^
/home/vexu/Documents/zig/zig/src/main.zig:4446:20: 0xa5285e7 in updateModule (zig)
    try comp.update(prog_node);
                   ^
/home/vexu/Documents/zig/zig/src/main.zig:3636:21: 0xa58f4d3 in buildOutputType (zig)
        updateModule(comp, color, root_prog_node) catch |err| switch (err) {
                    ^
/home/vexu/Documents/zig/zig/src/main.zig:273:31: 0xa41e4f1 in mainArgs (zig)
        return buildOutputType(gpa, arena, args, .zig_test);
                              ^
/home/vexu/Documents/zig/zig/src/main.zig:205:20: 0xa41b325 in main (zig)
    return mainArgs(gpa, arena, args);
                   ^
/home/vexu/.config/Code - OSS/User/globalStorage/ziglang.vscode-zig/zig/linux-x86_64-0.14.0-dev.2547+77c63ac36/lib/std/start.zig:656:37: 0xa41ae2e in main (zig)
            const result = root.main() catch |err| {
                                    ^

@Vexu Vexu added the frontend Tokenization, parsing, AstGen, Sema, and Liveness. label Dec 23, 2024
@Vexu Vexu added this to the 0.15.0 milestone Dec 23, 2024
@Vexu Vexu changed the title Segfault on comptime value No error on comptime expression loading runtime value Dec 23, 2024
mlugg added a commit to mlugg/zig that referenced this issue Dec 24, 2024
@mlugg
Sema: ensure result of block_comptime is comptime-known
6e4d874 
Also, simplify the handling of this instruction; it was previously going
through a completely unnecessary runtime path. Who would write such
ridiculous code?! (It was me, I wrote it)

Resolves: ziglang#22296
@mlugg mlugg modified the milestones: 0.15.0, 0.14.0 Dec 24, 2024
@mlugg mlugg mentioned this issue Dec 24, 2024
Open
mlugg added a commit to mlugg/zig that referenced this issue Dec 29, 2024
@mlugg
compiler: ensure result of block_comptime is comptime-known
6717d96 
To avoid this PR regressing error messages, most of the work here has
gone towards improving error notes for why code was comptime-evaluated.
ZIR `block_comptime` now stores a "comptime reason", the enum for which
is also used by Sema. There are two types in Sema:

* `ComptimeReason` represents the reason we started evaluating something
  at comptime.
* `BlockComptimeReason` represents the reason a given block is evaluated
  at comptime; it's either a `ComptimeReason` with an attached source
  location, or it's because we're in a function which was called at
  comptime (and that function's `Block` should be consulted for the
  "parent" reason).

Every `Block` stores a `?BlockComptimeReason`. The old `is_comptime`
field is replaced with a trivial `isComptime()` method which returns
whether that reason is non-`null`.

Lastly, the handling for `block_comptime` has been simplified. It was
previously going through an unnecessary runtime-handling path; now, it
is a trivial sub block exited through a `break_inline` instruction.

Resolves: ziglang#22296
mlugg added a commit to mlugg/zig that referenced this issue Dec 30, 2024
@mlugg
compiler: ensure result of block_comptime is comptime-known
e45b0aa 
To avoid this PR regressing error messages, most of the work here has
gone towards improving error notes for why code was comptime-evaluated.
ZIR `block_comptime` now stores a "comptime reason", the enum for which
is also used by Sema. There are two types in Sema:

* `ComptimeReason` represents the reason we started evaluating something
  at comptime.
* `BlockComptimeReason` represents the reason a given block is evaluated
  at comptime; it's either a `ComptimeReason` with an attached source
  location, or it's because we're in a function which was called at
  comptime (and that function's `Block` should be consulted for the
  "parent" reason).

Every `Block` stores a `?BlockComptimeReason`. The old `is_comptime`
field is replaced with a trivial `isComptime()` method which returns
whether that reason is non-`null`.

Lastly, the handling for `block_comptime` has been simplified. It was
previously going through an unnecessary runtime-handling path; now, it
is a trivial sub block exited through a `break_inline` instruction.

Resolves: ziglang#22296
mlugg added a commit to mlugg/zig that referenced this issue Dec 30, 2024
@mlugg
compiler: ensure result of block_comptime is comptime-known
a985d30 
To avoid this PR regressing error messages, most of the work here has
gone towards improving error notes for why code was comptime-evaluated.
ZIR `block_comptime` now stores a "comptime reason", the enum for which
is also used by Sema. There are two types in Sema:

* `ComptimeReason` represents the reason we started evaluating something
  at comptime.
* `BlockComptimeReason` represents the reason a given block is evaluated
  at comptime; it's either a `ComptimeReason` with an attached source
  location, or it's because we're in a function which was called at
  comptime (and that function's `Block` should be consulted for the
  "parent" reason).

Every `Block` stores a `?BlockComptimeReason`. The old `is_comptime`
field is replaced with a trivial `isComptime()` method which returns
whether that reason is non-`null`.

Lastly, the handling for `block_comptime` has been simplified. It was
previously going through an unnecessary runtime-handling path; now, it
is a trivial sub block exited through a `break_inline` instruction.

Resolves: ziglang#22296
mlugg added a commit to mlugg/zig that referenced this issue Dec 30, 2024
@mlugg
compiler: ensure result of block_comptime is comptime-known
0d1cc94 
To avoid this PR regressing error messages, most of the work here has
gone towards improving error notes for why code was comptime-evaluated.
ZIR `block_comptime` now stores a "comptime reason", the enum for which
is also used by Sema. There are two types in Sema:

* `ComptimeReason` represents the reason we started evaluating something
  at comptime.
* `BlockComptimeReason` represents the reason a given block is evaluated
  at comptime; it's either a `ComptimeReason` with an attached source
  location, or it's because we're in a function which was called at
  comptime (and that function's `Block` should be consulted for the
  "parent" reason).

Every `Block` stores a `?BlockComptimeReason`. The old `is_comptime`
field is replaced with a trivial `isComptime()` method which returns
whether that reason is non-`null`.

Lastly, the handling for `block_comptime` has been simplified. It was
previously going through an unnecessary runtime-handling path; now, it
is a trivial sub block exited through a `break_inline` instruction.

Resolves: ziglang#22296
@mlugg mlugg closed this as completed in 6026a5f Dec 31, 2024
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bug Observed behavior contradicts documented or intended behavior frontend Tokenization, parsing, AstGen, Sema, and Liveness.
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Sema: ensure result of block_comptime is comptime-known mlugg/zig
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@mlugg @Vexu @kj4tmp