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rust-embedded / embedonomicon

How to bootstrap support for a no_std target
https://docs.rust-embedded.org/embedonomicon/
Apache License 2.0
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Fix linker error in memory layout example #51

Closed austinglaser closed 4 years ago

austinglaser commented 4 years ago

When following the example in the memory layout chapter, I found that linking with rustc 1.39.0 (command cargo rustc -- -C link-arg=-Tlink.x) produced the following error:

   Compiling no_std_app v0.1.0 (/home/austin/repos/personal/no_std_experiment)
error: linking with `rust-lld` failed: exit code: 1
  |
  = note: "rust-lld" "-flavor" "gnu" "-L" "/home/austin/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib" "/home/austin/repos/personal/no_std_experiment/target/thumbv7m-none-eabi/debug/deps/no_std_app-1e7c0fdb8e33f523.2ohn928r55zfdn1z.rcgu.o" "-o" "/home/austin/repos/personal/no_std_experiment/target/thumbv7m-none-eabi/debug/deps/no_std_app-1e7c0fdb8e33f523" "--gc-sections" "-L" "/home/austin/repos/personal/no_std_experiment/target/thumbv7m-none-eabi/debug/deps" "-L" "/home/austin/repos/personal/no_std_experiment/target/debug/deps" "-L" "/home/austin/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib" "-Bstatic" "/home/austin/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/librustc_std_workspace_core-9864ecb2f3ae85f5.rlib" "/home/austin/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/libcore-a54bcae7919f0f3f.rlib" "/home/austin/.rustup/toolchains/stable-x86_64-unknown-linux-gnu/lib/rustlib/thumbv7m-none-eabi/lib/libcompiler_builtins-a509ea259a1bcbbf.rlib" "-Tlink.x" "-Bdynamic"
  = note: rust-lld: error: no memory region specified for section '.ARM.exidx'

error: aborting due to previous error

error: could not compile `no_std_app`.

To learn more, run the command again with --verbose.

This can be solved by adding .ARM.exidx alone (no .* extension) to the /DISCARD/ portion of link.x. This change should be backwards compatible to older versions of tooling which, presumably, do not emit the bare top-level section.

Fixes #50

rust-highfive commented 4 years ago

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @therealprof (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

austinglaser commented 4 years ago

Turns out that a) this particular fix is incomplete, and b) it was needed anyway for #54. So I'm closing this PR in favor of that one