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rust: fix bindgen build error with fstrict-flex-arrays
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Commit df8fc4e ("kbuild: Enable -fstrict-flex-arrays=3") enabled
'-fstrict-flex-arrays=3' globally, but bindgen does not recognized this
compiler option, triggering the following build error:

 error: unknown argument: '-fstrict-flex-arrays=3', err: true

[ Miguel: Commit df8fc4e ("kbuild: Enable -fstrict-flex-arrays=3")
  did it so only conditionally (i.e. only if the C compiler supports
  it). This explains what Andrea was seeing: he was  compiling with a
  modern enough GCC, which enables the option, but with an old enough
  Clang. Andrea confirmed this was the case: he was using Clang 14 with
  GCC 13; and that Clang 15 worked for him.

  While it is possible to construct code (see mailing list for an
  example I came up with) where this could break, it is fairly
  contrived, and anyway GCC-built kernels with Rust enabled should
  only be used for experimentation until we get support for
  `rustc_codegen_gcc` and/or GCC Rust. So let's add this for the
  time being in case it helps somebody. ]

Add '-fstrict-flex-arrays' to the list of cflags that should be ignored
by bindgen.

Fixes: df8fc4e ("kbuild: Enable -fstrict-flex-arrays=3")
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Tested-by: Gary Guo <gary@garyguo.net>
Link: https://lore.kernel.org/r/20230815065346.131387-1-andrea.righi@canonical.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
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Andrea Righi authored and Miguel Ojeda committed Oct 12, 2023
1 parent 2a7e0a5 commit 344b6c0
Showing 1 changed file with 1 addition and 0 deletions.
1 change: 1 addition & 0 deletions rust/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -290,6 +290,7 @@ bindgen_skip_c_flags := -mno-fp-ret-in-387 -mpreferred-stack-boundary=% \
-fno-reorder-blocks -fno-allow-store-data-races -fasan-shadow-offset=% \
-fzero-call-used-regs=% -fno-stack-clash-protection \
-fno-inline-functions-called-once -fsanitize=bounds-strict \
-fstrict-flex-arrays=% \
--param=% --param asan-%

# Derived from `scripts/Makefile.clang`.
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