From: "jaruga (Jun Aruga)" <noreply@...>
Date: 2022-12-02T14:45:43+00:00
Subject: [ruby-core:111157] [Ruby master Bug#19174] YJIT configure "checking whether rustc works for YJIT... no" in rustc 1.65.0 on x86_64

Issue #19174 has been reported by jaruga (Jun Aruga).

----------------------------------------
Bug #19174: YJIT configure "checking whether rustc works for YJIT... no" in rustc 1.65.0 on x86_64
https://bugs.ruby-lang.org/issues/19174

* Author: jaruga (Jun Aruga)
* Status: Open
* Priority: Normal
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
On the latest master branch `11871e49c4fe493d6b958046969bc863f7fb6627` on Fedora 36,

```
$ uname -m
x86_64

$ which rustc
/bin/rustc

$ rustc --version
rustc 1.65.0 (Fedora 1.65.0-1.fc37)
```

I am seeing the "checking whether rustc works for YJIT... no".

```
$ ./autogen.sh
$ ./configure --enable-yjit 2>&1 | tee configure.log
...
checking for rustc... rustc
checking whether rustc works for YJIT... no
...
   * YJIT support:        yes
...
```

Seeing the code <https://github.com/ruby/ruby/blob/11871e49c4fe493d6b958046969bc863f7fb6627/configure.ac#L3744-L3760>, it is to check if the rustc is >= 1.58.0. And the used rustc is 1.65.0.

```
dnl check if rustc is recent enough to build YJIT (rustc >= 1.58.0)
```

I suspect that the checking logic might be something wrong. I checked why the checking logic fails with the modification below.

```
$ git diff
diff --git a/configure.ac b/configure.ac
index 79167a9c67..33a1b9540d 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3753,7 +3753,7 @@ AS_IF([test "$RUSTC" != "no"],
     dnl Fails in case rustc target doesn't match ruby target.
     dnl Can happen on Rosetta, for example.
     AS_IF([echo "#[cfg(target_arch = \"$YJIT_TARGET_ARCH\")]\n fn main() { let x = 1; format!(\"{x}\"); }" |
-            $RUSTC - --emit asm=/dev/null 2>/dev/null],
+            $RUSTC - --emit asm=/dev/null],
         [YJIT_RUSTC_OK=yes]
     )
     AC_MSG_RESULT($YJIT_RUSTC_OK)
```

```
$ ./autogen.sh

$ ./configure --enable-yjit 2>&1 | tee configure_debug.log
...
checking for rustc... rustc
checking whether rustc works for YJIT... error: unknown start of token: \
 --> <anon>:1:31
  |
1 | #[cfg(target_arch = "x86_64")]\n fn main() { let x = 1; format!("{x}"); }
  |                               ^

error: expected one of `!` or `::`, found keyword `fn`
 --> <anon>:1:34
  |
1 | #[cfg(target_arch = "x86_64")]\n fn main() { let x = 1; format!("{x}"); }
  |                                  ^^ expected one of `!` or `::`
error: aborting due to 2 previous errors

no
...
   * YJIT support:        yes
...
```

Is it intended behavior? Actually after running the `configure`, the `make` works.






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