Implement the dbg!(..) macro #54317

Centril · 2018-09-18T05:54:50Z

Implements the dbg!(..) macro due to #54306.
cc rust-lang/rfcs#2361

r? @alexcrichton

SimonSapin · 2018-09-18T08:00:09Z

Looks good, thanks!

@bors r+

bors · 2018-09-18T08:00:14Z

📌 Commit 0fa114d207b7e8bea3e5eef2dc8d8918763426ca has been approved by SimonSapin

fbstj · 2018-09-18T08:08:00Z

src/libstd/macros.rs

+macro_rules! dbg {
+    ($val:expr) => {
+        // Use of `match` here is intentional because it affects the lifetimes
+        // of temporaries - https://stackoverflow.com/a/48732525/1063961


is a Stack Overflow the best kind of link for this documentation? may be worth "archiving" as a blog post somewhere on the forge for example?

We can always update this to something better later -- I'd welcome a follow up PR if you have ideas :)
I think it is sufficient for now.

kennytm · 2018-09-20T15:18:02Z

src/test/ui/rfc-2361-dbg-macro/dbg-macro-move-semantics.nll.stderr

+   = note: move occurs because `a` has type `NoCopy`, which does not implement the `Copy` trait
+   = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
+
+error: aborting due to 3 previous errors


[01:03:52] ---- [ui (nll)] ui/rfc-2361-dbg-macro/dbg-macro-move-semantics.rs stdout ---- [01:03:52] diff of stderr: [01:03:52] [01:03:52] 9 = note: move occurs because `a` has type `NoCopy`, which does not implement the `Copy` trait [01:03:52] 10 = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info) [01:03:52] 11 [01:03:52] - error[E0382]: borrow of moved value: `a` [01:03:52] - --> $DIR/dbg-macro-move-semantics.rs:11:18 [01:03:52] - | [01:03:52] - LL | let _ = dbg!(a); [01:03:52] - | ------- value moved here [01:03:52] - LL | let _ = dbg!(a); [01:03:52] - | ^ value borrowed here after move [01:03:52] - | [01:03:52] - = note: move occurs because `a` has type `NoCopy`, which does not implement the `Copy` trait [01:03:52] - = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info) [01:03:52] - [01:03:52] - error[E0382]: use of moved value: `a` [01:03:52] - --> $DIR/dbg-macro-move-semantics.rs:11:13 [01:03:52] - | [01:03:52] - LL | let _ = dbg!(a); [01:03:52] - | ------- value moved here [01:03:52] - LL | let _ = dbg!(a); [01:03:52] - | ^^^^^^^ value used here after move [01:03:52] - | [01:03:52] - = note: move occurs because `a` has type `NoCopy`, which does not implement the `Copy` trait [01:03:52] - = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info) [01:03:52] - [01:03:52] - error: aborting due to 3 previous errors [01:03:52] + error: aborting due to previous error [01:03:52] 35 [01:03:52] 36 For more information about this error, try `rustc --explain E0382`. [01:03:52] 37

kennytm · 2018-09-20T15:19:48Z

@bors r-

NLL changes probably changed diagnostics, causing failure in #54389 (comment). Could you rebase on latest master and verify if the CI still passes?

kennytm · 2018-09-21T02:33:44Z

@bors r=SimonSapin

bors · 2018-09-21T02:33:45Z

📌 Commit 924a693 has been approved by SimonSapin

@alexcrichton

…apin Implement the dbg!(..) macro Implements the `dbg!(..)` macro due to rust-lang#54306. cc rust-lang/rfcs#2361 r? @alexcrichton

Rollup of 10 pull requests Successful merges: - #53652 (define copy_within on slices) - #54261 (Make `dyn` a keyword in the 2018 edition) - #54317 (Implement the dbg!(..) macro) - #54323 (rustbuild: drop color handling) - #54371 (add -Zui-testing to rustdoc) - #54374 (Make 'proc_macro::MultiSpan' public.) - #54402 (Use no_default_libraries for all NetBSD flavors) - #54412 (add applicability to span_suggestion call) - #54413 (Add UI test for deref recursion limit printing twice) - #54422 (Simplify slice's first(_mut) and last(_mut) with get)

pietroalbini · 2018-09-22T07:53:05Z

Tests failed on wasm.
@bors r-

[00:59:02] ---- [ui] ui/rfc-2361-dbg-macro/dbg-macro-expected-behavior.rs stdout ----
[00:59:02] error: test run failed!
[00:59:02] status: exit code: 101
[00:59:02] status: exit code: 101
[00:59:02] command: "/node-v9.2.0-linux-x64/bin/node" "/checkout/src/etc/wasm32-shim.js" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/rfc-2361-dbg-macro/dbg-macro-expected-behavior/a.wasm"
[00:59:02] ------------------------------------------
[00:59:02] 
[00:59:02] ------------------------------------------
[00:59:02] stderr:
[00:59:02] stderr:
[00:59:02] ------------------------------------------
[00:59:02] RuntimeError: unreachable
[00:59:02]     at __rust_start_panic (wasm-function[148]:1)
[00:59:02]     at rust_panic.llvm.7229658430215002035 (wasm-function[142]:38)
[00:59:02]     at std::panicking::rust_panic_with_hook::h226a58a5977f2e17 (wasm-function[137]:500)
[00:59:02]     at std::panicking::continue_panic_fmt::h5f0126bd5d9da93f (wasm-function[136]:155)
[00:59:02]     at rust_begin_unwind (wasm-function[135]:3)
[00:59:02]     at core::panicking::panic_fmt::hebc42c0af7746402 (wasm-function[245]:80)
[00:59:02]     at core::result::unwrap_failed::hb8e1b756b0aad0f7 (wasm-function[19]:149)
[00:59:02]     at _$LT$core..result..Result$LT$T$C$$u20$E$GT$$GT$::unwrap::h047f9d6689dc96bf (wasm-function[1]:43)
[00:59:02]     at dbg_macro_expected_behavior::main::h80c10857552d47ce (wasm-function[6]:2332)
[00:59:02]     at std::rt::lang_start::_$u7b$$u7b$closure$u7d$$u7d$::hffb7cd8ec38eb3e9 (wasm-function[9]:25)
[00:59:02]     at std::sys_common::backtrace::__rust_begin_short_backtrace::h178ce1cdbcfd3352 (wasm-function[68]:8)
[00:59:02]     at std::panicking::try::do_call::h92ed3f8ab1f1fe4c (.llvm.7229658430215002035) (wasm-function[134]:20)
[00:59:02]     at __rust_maybe_catch_panic (wasm-function[147]:5)
[00:59:02]     at std::rt::lang_start_internal::had2eaac6c6c88dfd (wasm-function[69]:150)
[00:59:02]     at std::rt::lang_start::hecee5b62d0f0e846 (wasm-function[8]:42)
[00:59:02]     at main (wasm-function[7]:11)
[00:59:02]     at Object.<anonymous> (/checkout/src/etc/wasm32-shim.js:136:20)
[00:59:02]     at Module._compile (module.js:641:30)
[00:59:02]     at Object.Module._extensions..js (module.js:652:10)
[00:59:02]     at Module.load (module.js:560:32)
[00:59:02] ------------------------------------------
[00:59:02] 
[00:59:02] 
[00:59:02] thread '[ui] ui/rfc-2361-dbg-macro/dbg-macro-expected-behavior.rs' panicked at 'explicit panic', tools/compiletest/src/runtest.rs:3205:9

SimonSapin · 2018-09-22T16:09:29Z

@bors r+

bors · 2018-09-22T16:09:30Z

📌 Commit b4d6d78 has been approved by SimonSapin

bors · 2018-09-23T06:30:06Z

⌛ Testing commit b4d6d78 with merge bafca5b907c03dd861329a23bfea60a5a00acf04...

bors · 2018-09-23T07:38:12Z

💔 Test failed - status-travis

Centril · 2018-09-23T13:35:34Z

Same error...
I'm confused as to why the test is still running on wasm...

Centril · 2018-09-23T13:51:24Z

I added per @eddyb's notes:

// ignore-wasm32
// ignore-cloudabi no processes
// ignore-emscripten no processes

Let's hope that makes it work :)

Centril · 2018-09-23T14:00:44Z

I changed it to:

// run-pass
// ignore-cloudabi no processes
// ignore-emscripten no processes

since that's what the other tests do and that's more aligned with eddyb's and varkor's thoughts.

varkor · 2018-09-25T01:24:33Z

@bors r=SimonSapin

bors · 2018-09-25T01:24:33Z

📌 Commit e5b9331 has been approved by SimonSapin

bors · 2018-09-25T07:06:22Z

⌛ Testing commit e5b9331 with merge e7416d5...

@alexcrichton

Implement the dbg!(..) macro Implements the `dbg!(..)` macro due to #54306. cc rust-lang/rfcs#2361 r? @alexcrichton

bors · 2018-09-25T09:32:55Z

☀️ Test successful - status-appveyor, status-travis
Approved by: SimonSapin
Pushing e7416d5 to master...

RoelKluin · 2019-01-20T00:47:17Z

The dbg macro lacks a possibility to format the output. For instance, it is not possible to print an u64 as hexadecimal. Therefore, I was thinking about below macro that, when given more than one expression, does allow formatting:

#[macro_export]
macro_rules! dbg {
    ($expr:expr) => (dbg!("{:#?}", $expr));
    ($fmt:expr, $expr:expr$(, $opt:expr)*) => {
        match $expr {
            expr => {
                eprintln!(concat!("[{}:{}] {} = ", $fmt), file!(), line!(), stringify!($expr), &expr$(, $opt)*);
                expr
            }
        }
    }
}

With a single argument this behaves like current dbg, In case there are 2 or more, the first argument is a string literal format string, the second is the evaluated, optional remaining arguments can be provided as specified in the format string.

example:

let t = dbg!(2 + 1);

// instead of:
let _: u64 = dbg!((1 << 63) | (t << 8));

// this gives a nicer representation:
let _: u64 = dbg!("0x{:x}", (1 << 63) | (t << 8));
    
// also possible:
let _: u64 = dbg!("0x{:x}, with t={}", (1 << 63) | (t << 8), t);

rust-highfive assigned alexcrichton Sep 18, 2018

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Centril mentioned this pull request Sep 18, 2018

Tracking issue for RFC 2361, "Simpler alternative dbg!() macro" #54306

Closed

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fbstj reviewed Sep 18, 2018

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kennytm mentioned this pull request Sep 20, 2018

Rollup of 15 pull requests #54389

Merged

kennytm reviewed Sep 20, 2018

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bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Sep 20, 2018

Centril added 6 commits September 20, 2018 17:39

dbg!(expr) implementation.

000be8f

dbg_macro: feature gate + move semantics test.

cbb81bd

dbg_macro: Debug-required test.

6d08821

dbg_macro: output tests.

a9d2f38

dbg_macro: notes about VCS and log::debug!(..)

1d2a1bf

debug_macro: --bless tests.

924a693

Centril force-pushed the feature/dbg_macro branch from 0fa114d to 924a693 Compare September 20, 2018 16:02

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kennytm mentioned this pull request Sep 21, 2018

Rollup of 10 pull requests #54432

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dbg_macro: more things...

3006d4e

dbg_macro: only ignore cloudabi and emscripten

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dbg_macro: fix line numbers

e5b9331

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 25, 2018

bors added a commit that referenced this pull request Sep 25, 2018

Auto merge of #54317 - Centril:feature/dbg_macro, r=SimonSapin

e7416d5

Implement the dbg!(..) macro Implements the `dbg!(..)` macro due to #54306. cc rust-lang/rfcs#2361 r? @alexcrichton

bors merged commit e5b9331 into rust-lang:master Sep 25, 2018

Centril deleted the feature/dbg_macro branch October 3, 2018 22:20

RoelKluin mentioned this pull request Jan 22, 2019

Stabilize dbg!(...) #56395

Merged

Implement the dbg!(..) macro #54317

Implement the dbg!(..) macro #54317

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