make `CStr::from_bytes_with_nul_unchecked()` a const fn #54745

abonander · 2018-10-02T10:44:46Z

rust-highfive · 2018-10-02T10:44:57Z

(rust_highfive has picked a reviewer for you, use r? to override)

abonander · 2018-10-02T10:46:20Z

Not sure if this needs a test to confirm the ability to use this in a const, I guess as a regression test if this were to be removed.

rust-highfive · 2018-10-02T10:51:43Z

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:04:58]    Compiling alloc v0.0.0 (/checkout/src/liballoc)
[00:04:59]    Compiling alloc_system v0.0.0 (/checkout/src/liballoc_system)
[00:04:59]    Compiling panic_abort v0.0.0 (/checkout/src/libpanic_abort)
[00:05:03]    Compiling panic_unwind v0.0.0 (/checkout/src/libpanic_unwind)
[00:05:08] error: call to unsafe function is unsafe and unsafe operations are not allowed in const fn
[00:05:08]      |
[00:05:08]      |
[00:05:08] 1044 |         mem::transmute(bytes)
[00:05:08]      |         ^^^^^^^^^^^^^^^^^^^^^ call to unsafe function
[00:05:08]      |
[00:05:08]      = note: consult the function's documentation for information on how to avoid undefined behavior
[00:05:08] error: aborting due to previous error
[00:05:08] 
[00:05:08] error: Could not compile `std`.
[00:05:08] 
[00:05:08] 
[00:05:08] To learn more, run the command again with --verbose.
[00:05:08] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "build" "--target" "x86_64-unknown-linux-gnu" "-j" "4" "--release" "--locked" "--color" "always" "--features" "panic-unwind jemalloc backtrace" "--manifest-path" "/checkout/src/libstd/Cargo.toml" "--message-format" "json"
[00:05:08] expected success, got: exit code: 101
[00:05:08] thread 'main' panicked at 'cargo must succeed', bootstrap/compile.rs:1112:9
[00:05:08] travis_fold:end:stage0-std

[00:05:08] travis_time:end:stage0-std:start=1538477459977074430,finish=1538477497042180674,duration=37065106244

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

abonander · 2018-10-02T10:55:14Z

@oli-obk little snag with const_transmute here

oli-obk · 2018-10-02T11:09:10Z

src/libstd/ffi/c_str.rs

@@ -1040,8 +1040,8 @@ impl CStr {
    /// ```
    #[inline]
    #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-    pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
-        &*(bytes as *const [u8] as *const CStr)


Oh. I should have checked the original source :D You should be able to just add #![feature(const_raw_ptr_deref)] and keep the original source ;)

src/libstd/ffi/c_str.rs

oli-obk · 2018-10-02T11:10:59Z

Not sure if this needs a test to confirm the ability to use this in a const, I guess as a regression test if this were to be removed.

A test would be great, yes.

abonander · 2018-10-02T11:15:54Z

r? @oli-obk

abonander · 2018-10-02T11:16:44Z

src/libstd/ffi/c_str.rs

@@ -1040,7 +1040,8 @@ impl CStr {
    /// ```
    #[inline]
    #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-    pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
+    #[rustc_const_unstable]
+    pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {


@oli-obk preferred ordering of the attributes? shortest to longest or doesn't really matter?

I don't think it matters. I ususally put the const unstable attribute below the stable attribute

Done, and added it to the crate feature flags as well.

oli-obk · 2018-10-02T11:17:30Z

src/libstd/ffi/c_str.rs

@@ -1040,7 +1040,8 @@ impl CStr {
    /// ```
    #[inline]
    #[stable(feature = "cstr_from_bytes", since = "1.10.0")]
-    pub unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
+    #[rustc_const_unstable]


you need to specify a feature name like in

rust/src/test/ui/feature-gates/feature-gate-rustc_const_unstable.rs

Line 18 in f45f525

#[rustc_const_unstable(feature="fzzzzzt")] //~ERROR internal feature

Should I just make one up or what?

jup :D that's how feature names work

rust-highfive · 2018-10-02T11:22:22Z

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

[00:04:52]    Compiling alloc v0.0.0 (/checkout/src/liballoc)
[00:04:53]    Compiling alloc_system v0.0.0 (/checkout/src/liballoc_system)
[00:04:53]    Compiling panic_abort v0.0.0 (/checkout/src/libpanic_abort)
[00:04:57]    Compiling panic_unwind v0.0.0 (/checkout/src/libpanic_unwind)
[00:04:59] error[E0548]: incorrect stability attribute type
[00:04:59]      |
[00:04:59] 1043 |     #[rustc_const_unstable]
[00:04:59]      |     ^^^^^^^^^^^^^^^^^^^^^^^
[00:04:59] 
---
[00:05:01] 
[00:05:01] To learn more, run the command again with --verbose.
[00:05:01] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "build" "--target" "x86_64-unknown-linux-gnu" "-j" "4" "--release" "--locked" "--color" "always" "--features" "panic-unwind jemalloc backtrace" "--manifest-path" "/checkout/src/libstd/Cargo.toml" "--message-format" "json"
[00:05:01] expected success, got: exit code: 101
[00:05:01] thread 'main' panicked at 'cargo must succeed', bootstrap/compile.rs:1112:9
[00:05:01] travis_fold:end:stage0-std

[00:05:01] travis_time:end:stage0-std:start=1538479266326394735,finish=1538479303466363965,duration=37139969230


[00:05:01] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap build
[00:05:01] Build completed unsuccessfully in 0:00:38
[00:05:01] make: *** [all] Error 1
[00:05:01] Makefile:28: recipe for target 'all' failed

The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:08ccbdf5
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
---
travis_time:end:26a7a514:start=1538479304164944651,finish=1538479304170228523,duration=5283872
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:072432a7
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:03aefab2
travis_time:start:03aefab2
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:0965d8e0
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

closes rust-lang#54678

oli-obk · 2018-10-02T11:31:01Z

@bors r+

bors · 2018-10-02T11:31:02Z

📌 Commit e0caaec has been approved by oli-obk

make `CStr::from_bytes_with_nul_unchecked()` a const fn closes rust-lang#54678

@ghost

Rollup of 10 pull requests Successful merges: - #54269 (#53840: Consolidate pattern check errors) - #54458 (Allow both explicit and elided lifetimes in the same impl header) - #54603 (Add `crate::` to trait suggestions in Rust 2018.) - #54648 (Update Cargo's submodule) - #54680 (make run-pass tests with empty main just compile-pass tests) - #54687 (Use impl_header_lifetime_elision in libcore) - #54699 (Re-export `getopts` so custom drivers can reference it.) - #54702 (do not promote comparing function pointers) - #54728 (Renumber `proc_macro` tracking issues) - #54745 (make `CStr::from_bytes_with_nul_unchecked()` a const fn) Failed merges: r? @ghost

rust-highfive assigned dtolnay Oct 2, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Oct 2, 2018

oli-obk reviewed Oct 2, 2018

View reviewed changes

src/libstd/ffi/c_str.rs Show resolved Hide resolved

abonander force-pushed the cstr-const branch from 380fb2b to 4b37404 Compare October 2, 2018 11:14

rust-highfive assigned oli-obk and unassigned dtolnay Oct 2, 2018

abonander commented Oct 2, 2018

View reviewed changes

oli-obk reviewed Oct 2, 2018

View reviewed changes

make CStr::from_bytes_with_nul_unchecked() a const fn

092bf2b

closes rust-lang#54678

abonander force-pushed the cstr-const branch from 4b37404 to 092bf2b Compare October 2, 2018 11:25

make CStr::from_bytes_with_nul_unchecked() a const fn

e0caaec

closes rust-lang#54678

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-review Status: Awaiting review from the assignee but also interested parties. labels Oct 2, 2018

pietroalbini added a commit to pietroalbini/rust that referenced this pull request Oct 2, 2018

Rollup merge of rust-lang#54745 - abonander:cstr-const, r=oli-obk

926431b

make `CStr::from_bytes_with_nul_unchecked()` a const fn closes rust-lang#54678

pietroalbini mentioned this pull request Oct 2, 2018

Rollup of 10 pull requests #54763

Closed

pietroalbini added a commit to pietroalbini/rust that referenced this pull request Oct 2, 2018

Rollup merge of rust-lang#54745 - abonander:cstr-const, r=oli-obk

00e4b27

make `CStr::from_bytes_with_nul_unchecked()` a const fn closes rust-lang#54678

pietroalbini mentioned this pull request Oct 2, 2018

Rollup of 10 pull requests #54767

Merged

bors merged commit e0caaec into rust-lang:master Oct 3, 2018

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

make `CStr::from_bytes_with_nul_unchecked()` a const fn #54745

make `CStr::from_bytes_with_nul_unchecked()` a const fn #54745

abonander commented Oct 2, 2018

rust-highfive commented Oct 2, 2018

abonander commented Oct 2, 2018

rust-highfive commented Oct 2, 2018

abonander commented Oct 2, 2018

oli-obk Oct 2, 2018

oli-obk commented Oct 2, 2018

abonander commented Oct 2, 2018

abonander Oct 2, 2018

oli-obk Oct 2, 2018

abonander Oct 2, 2018

oli-obk Oct 2, 2018

abonander Oct 2, 2018

oli-obk Oct 2, 2018

rust-highfive commented Oct 2, 2018

oli-obk commented Oct 2, 2018

bors commented Oct 2, 2018

make CStr::from_bytes_with_nul_unchecked() a const fn #54745

make CStr::from_bytes_with_nul_unchecked() a const fn #54745

Conversation

abonander commented Oct 2, 2018

rust-highfive commented Oct 2, 2018

abonander commented Oct 2, 2018

rust-highfive commented Oct 2, 2018

abonander commented Oct 2, 2018

oli-obk Oct 2, 2018

Choose a reason for hiding this comment

oli-obk commented Oct 2, 2018

abonander commented Oct 2, 2018

abonander Oct 2, 2018

Choose a reason for hiding this comment

oli-obk Oct 2, 2018

Choose a reason for hiding this comment

abonander Oct 2, 2018

Choose a reason for hiding this comment

oli-obk Oct 2, 2018

Choose a reason for hiding this comment

abonander Oct 2, 2018

Choose a reason for hiding this comment

oli-obk Oct 2, 2018

Choose a reason for hiding this comment

rust-highfive commented Oct 2, 2018

oli-obk commented Oct 2, 2018

bors commented Oct 2, 2018

make `CStr::from_bytes_with_nul_unchecked()` a const fn #54745

make `CStr::from_bytes_with_nul_unchecked()` a const fn #54745