[PATCH v6 2/2] rust: Makefile: bound rustdoc workaround to affected versions

[HeeSu Kim]

The `-Cunsafe-allow-abi-mismatch=fixed-x18` workaround was added to
handle a rustdoc bug where target modifiers were not properly saved [1].
An analogous workaround for doctests was added later [2]; since Rust
1.91.0 the `sanitizer` modifier is also appended.

The rustdoc bug is fixed in Rust 1.90.0 [3] and the doctests one is
fixed in Rust 1.92.0, so restrict each workaround to the compiler
versions that are actually affected, letting ABI compatibility checks
run again on newer compilers.

Split the cases into explicit version ranges using
`rustc-min-version` + `rustc-lt-version` combined inline: the rustdoc
workaround applies to 1.88.x and 1.89.x, the doctests workaround to
1.88.x through 1.91.x, and the `sanitizer` modifier is only added
from 1.91.x onwards (when rustc started recognizing it). This layout
makes it easy to drop each entry as the minimum toolchain version is
bumped past the affected range.

[1] https://github.com/rust-lang/rust/issues/144521
[2] https://github.com/rust-lang/rust/issues/146465
[3] https://github.com/rust-lang/rust/pull/144523

Suggested-by: Gary Guo <gary@xxxxxxxxxxx>
Link: https://lore.kernel.org/rust-for-linux/DG4JM9PU51M0.1YRGM9HVTY24U@xxxxxxxxxxx/
Suggested-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Link: https://lore.kernel.org/rust-for-linux/CANiq72nnuKJaKrxrut6+noR13PUiSoWWyyp-pGx-fe_2O6ayFA@xxxxxxxxxxxxxx/
Cc: stable@xxxxxxxxxxxxxxx # Useful in 6.18.y and later.
Signed-off-by: HeeSu Kim <mlksvender@xxxxxxxxx>
---
 rust/Makefile | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/rust/Makefile b/rust/Makefile
index 5c0155b83454..14acc9c57c60 100644
--- a/rust/Makefile
+++ b/rust/Makefile
@@ -134,12 +134,18 @@ pin_init-flags := \
     --extern macros \
     $(call cfgs-to-flags,$(pin_init-cfgs))
 
-# `rustdoc` did not save the target modifiers, thus workaround for
-# the time being (https://github.com/rust-lang/rust/issues/144521).
-rustdoc_modifiers_workaround := $(if $(call rustc-min-version,108800),-Cunsafe-allow-abi-mismatch=fixed-x18)
-
-# Similarly, for doctests (https://github.com/rust-lang/rust/issues/146465).
-doctests_modifiers_workaround := $(rustdoc_modifiers_workaround)$(if $(call rustc-min-version,109100),$(comma)sanitizer)
+# `rustdoc` did not save the target modifiers
+# (https://github.com/rust-lang/rust/issues/144521, fixed in Rust 1.90.0).
+# Similarly, for doctests
+# (https://github.com/rust-lang/rust/issues/146465, fixed in Rust 1.92.0).
+ifeq ($(and $(call rustc-min-version,108800),$(call rustc-lt-version,109000)),y)
+rustdoc_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+else ifeq ($(and $(call rustc-min-version,109000),$(call rustc-lt-version,109100)),y)
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18
+else ifeq ($(and $(call rustc-min-version,109100),$(call rustc-lt-version,109200)),y)
+doctests_modifiers_workaround := -Cunsafe-allow-abi-mismatch=fixed-x18,sanitizer
+endif
 
 # `rustc` recognizes `--remap-path-prefix` since 1.26.0, but `rustdoc` only
 # since Rust 1.81.0. Moreover, `rustdoc` ICEs on out-of-tree builds since Rust
-- 
2.52.0