add debug assertion to `unreachable_unchecked` #90915

ibraheemdev · 2021-11-15T00:28:09Z

No description provided.

rust-highfive · 2021-11-15T00:28:11Z

(rust-highfive has picked a reviewer for you, use r? to override)

joshtriplett · 2021-11-16T23:37:09Z

I'd like to understand better whether this specific debug_assert will get compiled out of programs when built in release mode.

Would it make sense for us to make this #[inline(always)] to ensure that?

Mark-Simulacrum · 2021-11-17T00:04:59Z

It wouldn't even get codegen'd - std is not shipped with debug assertions on, so it shouldn't get generated anywhere.

I'd probably implement this as an explicit cfg(...) around a panic, though, rather than debug_assert with a false argument.

ibraheemdev · 2021-11-17T01:27:07Z

error: `panic` is not yet stable as a const fn
    |
23  | / pub macro panic_2015 {
24  | |     () => (
25  | |         $crate::panicking::panic("explicit panic")
---
12  | |     };
13  | | }
    | |_- in this expansion of `panic!` (#2)
...
214 | / macro_rules! debug_assert {
215 | |     ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert!($($arg)*); })
    | |                                                           |
    | |                                                           in this macro invocation (#2)
    | |                                                           in this macro invocation (#3)
216 | | }
216 | | }

Why is this failing? unreachable_unchecked is const-stable from 1.57, as of which const-panic is stable, right?

camsteffen · 2021-11-17T17:22:00Z

How about #[cfg_attr(debug_assertions, track_caller)] as well?

camsteffen · 2021-11-17T17:26:15Z

library/core/src/hint.rs

@@ -46,6 +46,7 @@ use crate::intrinsics;
 #[stable(feature = "unreachable", since = "1.27.0")]
 #[rustc_const_stable(feature = "const_unreachable_unchecked", since = "1.57.0")]
 pub const unsafe fn unreachable_unchecked() -> ! {
+    debug_assert!(false, "entered unreachable code");


just a suggestion, to be more informative

Suggested change

debug_assert!(false, "entered unreachable code");

debug_assert!(false, "called `unreachable_unchecked`");

newpavlov · 2021-11-23T17:05:26Z

See #51713 for discussion about adding debug asserts to std/core code.

JohnCSimon · 2021-12-12T03:48:40Z

ping from triage:
@ibraheemdev
Returning to you to address build failures and after that, please switch back to S-waiting-on-review.
thanks.

@rustbot label: +S-waiting-on-author -S-waiting-on-review

rust-log-analyzer · 2021-12-12T05:09:47Z

The job x86_64-gnu-llvm-12 failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

- LL |     unsafe { intrinsics::unreachable() }
-    |              ^^^^^^^^^^^^^^^^^^^^^^^^^
-    |              |
-    |              entering unreachable code
-    |              inside `unreachable_unchecked` at $SRC_DIR/core/src/hint.rs:LL:COL
+ LL |     debug_assert!(false, "entered unreachable code");
Some tests failed in compiletest suite=ui mode=ui host=x86_64-unknown-linux-gnu target=x86_64-unknown-linux-gnu
+    |     |
+    |     |
+    |     the evaluated program panicked at 'entered unreachable code', $SRC_DIR/core/src/hint.rs:LL:COL
+    |     inside `unreachable_unchecked` at $SRC_DIR/core/src/panic.rs:LL:COL
10   ::: $DIR/const_unsafe_unreachable_ub.rs:6:18
11    |

14 ...
14 ...
15 LL | const BAR: bool = unsafe { foo(false) };
16    |                            ---------- inside `BAR` at $DIR/const_unsafe_unreachable_ub.rs:10:28
+    = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)
17 
18 error: aborting due to previous error
19 
19 


The actual stderr differed from the expected stderr.
Actual stderr saved to /checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const_unsafe_unreachable_ub/const_unsafe_unreachable_ub.stderr
To only update this specific test, also pass `--test-args consts/const_unsafe_unreachable_ub.rs`

error: 1 errors occurred comparing output.
status: exit status: 1
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/consts/const_unsafe_unreachable_ub.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "--emit" "metadata" "-C" "prefer-dynamic" "--out-dir" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const_unsafe_unreachable_ub" "-A" "unused" "-Crpath" "-O" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/consts/const_unsafe_unreachable_ub/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error[E0080]: evaluation of constant value failed
  --> /checkout/library/core/src/hint.rs:49:5
   |
LL |     debug_assert!(false, "entered unreachable code");
   |     |
   |     |
   |     the evaluated program panicked at 'entered unreachable code', /checkout/library/core/src/hint.rs:49:5
   |     inside `unreachable_unchecked` at /checkout/library/core/src/panic.rs:28:9
  ::: /checkout/src/test/ui/consts/const_unsafe_unreachable_ub.rs:6:18
   |
LL |         false => std::hint::unreachable_unchecked(),
   |                  ---------------------------------- inside `foo` at /checkout/src/test/ui/consts/const_unsafe_unreachable_ub.rs:6:18
   |                  ---------------------------------- inside `foo` at /checkout/src/test/ui/consts/const_unsafe_unreachable_ub.rs:6:18
...
LL | const BAR: bool = unsafe { foo(false) };
   |                            ---------- inside `BAR` at /checkout/src/test/ui/consts/const_unsafe_unreachable_ub.rs:10:28
   = note: this error originates in the macro `$crate::panic::panic_2015` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error


For more information about this error, try `rustc --explain E0080`.

------------------------------------------


---- [ui] ui/extern/issue-64655-extern-rust-must-allow-unwind.rs#fat0 stdout ----

error in revision `fat0`: test compilation failed although it shouldn't!
status: exit status: 1
command: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "/checkout/src/test/ui/extern/issue-64655-extern-rust-must-allow-unwind.rs" "-Zthreads=1" "--target=x86_64-unknown-linux-gnu" "--cfg" "fat0" "--error-format" "json" "--json" "future-incompat" "-Ccodegen-units=1" "-Zui-testing" "-Zdeduplicate-diagnostics=no" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/extern/issue-64655-extern-rust-must-allow-unwind.fat0/a" "-Crpath" "-Cdebuginfo=0" "-Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-C" "opt-level=0" "-C" "lto=fat" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/extern/issue-64655-extern-rust-must-allow-unwind.fat0/auxiliary"
------------------------------------------

------------------------------------------
stderr:
stderr:
------------------------------------------
error: linking with `cc` failed: exit status: 1
   |
   = note: "cc" "-m64" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/extern/issue-64655-extern-rust-must-allow-unwind.fat0/a.issue_64655_extern_rust_must_allow_unwind.a241db93-cgu.0.rcgu.o" "-Wl,--as-needed" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/extern/issue-64655-extern-rust-must-allow-unwind.fat0/auxiliary" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,--start-group" "-Wl,--end-group" "-Wl,-Bstatic" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-e934c84b0c8fe00e.rlib" "-Wl,-Bdynamic" "-lgcc_s" "-lutil" "-lrt" "-lpthread" "-lm" "-ldl" "-lc" "-Wl,--eh-frame-hdr" "-Wl,-znoexecstack" "-L" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-o" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui/extern/issue-64655-extern-rust-must-allow-unwind.fat0/a" "-Wl,--gc-sections" "-pie" "-Wl,-zrelro,-znow" "-nodefaultlibs" "-Wl,-rpath,$ORIGIN/../../../../stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,--enable-new-dtags"
   = note: /usr/bin/ld: /checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcompiler_builtins-e934c84b0c8fe00e.rlib(compiler_builtins-e934c84b0c8fe00e.compiler_builtins.eb3cb2f1-cgu.38.rcgu.o): in function `core::hint::unreachable_unchecked':
           compiler_builtins.eb3cb2f1-cgu.38:(.text._ZN4core4hint21unreachable_unchecked17h360525a5b2d0b3d0E+0x16): undefined reference to `core::panicking::panic'
           collect2: error: ld returned 1 exit status
           
   = help: some `extern` functions couldn't be found; some native libraries may need to be installed or have their path specified
   = note: use the `-l` flag to specify native libraries to link
   = note: use the `cargo:rustc-link-lib` directive to specify the native libraries to link with Cargo (see https://doc.rust-lang.org/cargo/reference/build-scripts.html#cargorustc-link-libkindname)
error: aborting due to previous error


------------------------------------------
---
test result: FAILED. 12362 passed; 2 failed; 119 ignored; 0 measured; 0 filtered out; finished in 119.97s



command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0-tools-bin/compiletest" "--compile-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib" "--run-lib-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib" "--rustc-path" "/checkout/obj/build/x86_64-unknown-linux-gnu/stage2/bin/rustc" "--src-base" "/checkout/src/test/ui" "--build-base" "/checkout/obj/build/x86_64-unknown-linux-gnu/test/ui" "--stage-id" "stage2-x86_64-unknown-linux-gnu" "--suite" "ui" "--mode" "ui" "--target" "x86_64-unknown-linux-gnu" "--host" "x86_64-unknown-linux-gnu" "--llvm-filecheck" "/usr/lib/llvm-12/bin/FileCheck" "--nodejs" "/usr/bin/node" "--host-rustcflags" "-Crpath -O -Cdebuginfo=0  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--target-rustcflags" "-Crpath -O -Cdebuginfo=0  -Lnative=/checkout/obj/build/x86_64-unknown-linux-gnu/native/rust-test-helpers" "--docck-python" "/usr/bin/python3" "--lldb-python" "/usr/bin/python3" "--gdb" "/usr/bin/gdb" "--quiet" "--llvm-version" "12.0.0" "--llvm-components" "aarch64 aarch64asmparser aarch64codegen aarch64desc aarch64disassembler aarch64info aarch64utils aggressiveinstcombine all all-targets amdgpu amdgpuasmparser amdgpucodegen amdgpudesc amdgpudisassembler amdgpuinfo amdgpuutils analysis arm armasmparser armcodegen armdesc armdisassembler arminfo armutils asmparser asmprinter avr avrasmparser avrcodegen avrdesc avrdisassembler avrinfo binaryformat bitreader bitstreamreader bitwriter bpf bpfasmparser bpfcodegen bpfdesc bpfdisassembler bpfinfo cfguard codegen core coroutines coverage debuginfocodeview debuginfodwarf debuginfogsym debuginfomsf debuginfopdb demangle dlltooldriver dwarflinker engine executionengine extensions filecheck frontendopenacc frontendopenmp fuzzmutate globalisel hellonew hexagon hexagonasmparser hexagoncodegen hexagondesc hexagondisassembler hexagoninfo instcombine instrumentation interfacestub interpreter ipo irreader jitlink lanai lanaiasmparser lanaicodegen lanaidesc lanaidisassembler lanaiinfo libdriver lineeditor linker lto mc mca mcdisassembler mcjit mcparser mips mipsasmparser mipscodegen mipsdesc mipsdisassembler mipsinfo mirparser msp430 msp430asmparser msp430codegen msp430desc msp430disassembler msp430info native nativecodegen nvptx nvptxcodegen nvptxdesc nvptxinfo objcarcopts object objectyaml option orcjit orcshared orctargetprocess passes perfjitevents powerpc powerpcasmparser powerpccodegen powerpcdesc powerpcdisassembler powerpcinfo profiledata remarks riscv riscvasmparser riscvcodegen riscvdesc riscvdisassembler riscvinfo runtimedyld scalaropts selectiondag sparc sparcasmparser sparccodegen sparcdesc sparcdisassembler sparcinfo support symbolize systemz systemzasmparser systemzcodegen systemzdesc systemzdisassembler systemzinfo tablegen target textapi transformutils vectorize webassembly webassemblyasmparser webassemblycodegen webassemblydesc webassemblydisassembler webassemblyinfo windowsmanifest x86 x86asmparser x86codegen x86desc x86disassembler x86info xcore xcorecodegen xcoredesc xcoredisassembler xcoreinfo xray" "--system-llvm" "--cc" "" "--cxx" "" "--cflags" "" "--adb-path" "adb" "--adb-test-dir" "/data/tmp/work" "--android-cross-path" "" "--channel" "nightly" "--color" "always"


Build completed unsuccessfully in 0:11:29

JohnCSimon · 2022-01-23T01:20:29Z

Ping from triage:
@ibraheemdev can you post your status on this PR? It has sat idle for a while.

ibraheemdev · 2022-01-23T02:27:27Z

cc @RalfJung I'm not sure what to do about this test, which is now panicking.

RalfJung · 2022-01-23T23:29:35Z

I guess the test should check for the panic then?

The problem will rather be that behavior differs depending on how the standard library is compiled. For codegen tests we have // ignore-debug, I wonder if that also works for ui tests?

JohnCSimon · 2022-03-20T05:20:06Z

@ibraheemdev
Ping from triage: I'm closing this due to inactivity, Please reopen when you are ready to continue with this. Thanks for your contribution.

@rustbot label: +S-inactive

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camsteffen reviewed Nov 17, 2021

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ibraheemdev force-pushed the patch-8 branch from d9991d5 to 7675a50 Compare December 12, 2021 04:55

add debug assertion to unreachable_unchecked

7675a50

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add debug assertion to `unreachable_unchecked` #90915

add debug assertion to `unreachable_unchecked` #90915

ibraheemdev commented Nov 15, 2021

rust-highfive commented Nov 15, 2021

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ibraheemdev commented Nov 17, 2021

camsteffen commented Nov 17, 2021

camsteffen Nov 17, 2021

newpavlov commented Nov 23, 2021

JohnCSimon commented Dec 12, 2021

rust-log-analyzer commented Dec 12, 2021

JohnCSimon commented Jan 23, 2022

ibraheemdev commented Jan 23, 2022

RalfJung commented Jan 23, 2022

JohnCSimon commented Mar 20, 2022

	debug_assert!(false, "entered unreachable code");
	debug_assert!(false, "called `unreachable_unchecked`");

add debug assertion to unreachable_unchecked #90915

add debug assertion to unreachable_unchecked #90915

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JohnCSimon commented Jan 23, 2022

ibraheemdev commented Jan 23, 2022

RalfJung commented Jan 23, 2022

JohnCSimon commented Mar 20, 2022

add debug assertion to `unreachable_unchecked` #90915

add debug assertion to `unreachable_unchecked` #90915