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rustc silently ignores invalid -C target-feature names #44815
Description
Compiling a simple Hello, World program:
$ rustc -V
rustc 1.20.0 (f3d6973f4 2017-08-27)
# Note the trailing "zzzz"
$ RUSTFLAGS=-Ctarget-feature=+crt-staticzzzz cargo build -v
Compiling rust-test v0.1.0 (rust-test)
Running `rustc --crate-name rust_test src/main.rs --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=aafe1708c049ad76 -C extra-filename=-aafe1708c049ad76 --out-dir rust-test/target/debug/deps -L dependency=rust-test/target/debug/deps '-Ctarget-feature=+crt-staticzzzz'`
Finished dev [unoptimized + debuginfo] target(s) in 0.25 secs
Should RUSTFLAGS=-Ctarget-feature=+crt-staticzzzz be silently accepted?
If I pass RUSTFLAGS=-Ctarget-feature=+batman, a warning is printed, as expected.
'+batman' is not a recognized feature for this target (ignoring feature)
Why is trailing misspelling silently allowed?
Activity
zackmdavis commentedon Oct 2, 2017
This is happening inside LLVM and plausibly should be filed with that project.
hanna-kruppe commentedon Oct 2, 2017
crt-staticis not passed to LLVM (and shouldn't be). It seems as if rustc consumes not justcrt-staticbut also other target features that have it as a prefix? This filtering looks suspicious:rust/src/librustc_trans/back/write.rs
Lines 119 to 121 in ded38db
petrochenkov commentedon May 10, 2020
Also rustc:
+and-. I tried to find places in LLVM where this could break things, but found a couple at best. Memory sanitizer perhaps? https://github.com/rust-lang/llvm-project/blob/rustc/9.0-2019-12-19/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp#L3738. The main thing (subtarget creation) is done correctly.There's at least one such place in rustc (
"+atomics"check).+or-. I have no idea why the assert inMCSubtargetInfo.cpp/ApplyFeatureFlagdoesn't fire on this.Rollup merge of rust-lang#72094 - petrochenkov:overfeature, r=nikic
Rollup merge of rust-lang#72094 - petrochenkov:overfeature, r=nikic