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Add default compiler prefixes for thumbv7a/thumbv7r/thumbv8r bare-metal targets#1742

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NobodyXu merged 1 commit into
rust-lang:mainfrom
cezarbbb:add-thumb-target-prefixes
Jun 4, 2026
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Add default compiler prefixes for thumbv7a/thumbv7r/thumbv8r bare-metal targets#1742
NobodyXu merged 1 commit into
rust-lang:mainfrom
cezarbbb:add-thumb-target-prefixes

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@cezarbbb

@cezarbbb cezarbbb commented Jun 2, 2026

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These five Thumb-mode bare-metal Arm targets were recently promoted to Tier 2 in
rust-lang/rust(MCP is here). Without entries in get_default_prefix, the cc crate falls back to
the host compiler, which errors on -mthumb.

NobodyXu
NobodyXu requested changes Jun 3, 2026
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Thanks! Just a question

Comment thread src/lib.rs
"armv7r-none-eabihf" => Some("arm-none-eabi"),
"armv8r-none-eabihf" => Some("arm-none-eabi"),
"thumbv7a-none-eabi" => Some("arm-none-eabi"),
"thumbv7a-none-eabihf" => Some("arm-none-eabi"),

@NobodyXu NobodyXu Jun 3, 2026

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The description of the pr linked seems to match it to a arm-none-eabihf, as well as any target ends with hf

@cezarbbb

cezarbbb commented Jun 4, 2026

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Thank you so much for your review! I thought so too before, but the existing entries in this match arm already map all eabihf targets to arm-none-eabi — for example armv7a-none-eabihf, armv7r-none-eabihf, armv8r-none-eabihf, thumbv7em-none-eabihf, thumbv8m.main-none-eabihf all use arm-none-eabi. In fact I found that arm-none-eabihf is never used as a prefix anywhere in this crate. It seems the bare-metal toolchain ships as a single arm-none-eabi-gcc binary and handles hard-float via compiler flags (-mfloat-abi=hard) rather than a separate prefix. Therefore, I simply referred to the processing methods of other existing *-none-eabihf targets.

@cezarbbb cezarbbb requested a review from NobodyXu June 4, 2026 06:22
@NobodyXu

NobodyXu commented Jun 4, 2026

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Thank you!

I just remember that we use mfloat-abi instead of hf suffiz

cc-rs/src/lib.rs

Line 2384 in b49589a

cmd.args.push("-mfloat-abi=hard".into());

@NobodyXu NobodyXu merged commit b2e811e into rust-lang:main Jun 4, 2026
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@cezarbbb cezarbbb deleted the add-thumb-target-prefixes branch June 4, 2026 13:44
@github-actions github-actions Bot mentioned this pull request Jun 5, 2026
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@github-actions github-actions Bot mentioned this pull request Jun 12, 2026
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