Bug #19174: YJIT configure "checking whether rustc works for YJIT... no" in rustc 1.65.0 on x86_64

• Status: Closed
• Priority: Normal
• Assignee: -
• Target version: -
• Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN

[jaruga (Jun Aruga)]

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.

[alanwu (Alan Wu)]

That check is intended for automatically enabling YJIT when we can find a suitable rustc.
When we get --enable-yjit explicitly we listen to that and don't use the result of the check, which is what you're seeing. So it's fine.

That said, it looks like I messed up and assumed that "\n" gives a newline with echo. Apparently not in all shells!

[alanwu (Alan Wu)]

• Status changed from Open to Closed

Applied in changeset git|1015e69d37b8e75145a3d21e4bd54fa538d1fa68.

---

YJIT: echo "\n" is not portable

It's unspecified by POSIX. zsh and dash give a newline and
bash doesn't substitute it. Attributes don't have to be
followed by a newline anyway, so just remove it.

[Bug #19174]