cargo build fails: can't find crate for std

[wucke13]

The output of the error is the following:

   Compiling rust-toolchain v0.1.0 (/tmp/test)                                                                                                                                       
     Running `rustc --crate-name rust_toolchain src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=f8ada62e29834902 -C extra-filename=-f8ada62e29834902 --out-dir /tmp/test/target/thumbv7em-none-eabihf/debug/deps --target thumbv7em-none-eabihf -C incremental=/tmp/test/target/thumbv7em-none-eabihf/debug/incremental -L dependency=/tmp/test/target/thumbv7em-none-eabihf/debug/deps -L dependency=/tmp/test/target/debug/deps --extern stm32f3=/tmp/test/target/thumbv7em-none-eabihf/debug/deps/libstm32f3-89c96bc170109bc0.rlib -C link-arg=-Tlink.x -L /tmp/test/target/thumbv7em-none-eabihf/debug/build/stm32f3-7c665be50e2d2105/out -L '/home/wucke13/documents/people/Günther Kemnitz/rust-toolchain/target/thumbv7em-none-eabihf/debug/build/cortex-m-e093635255097b24/out' -L /tmp/test/target/thumbv7em-none-eabihf/debug/build/cortex-m-rt-28a646978498040b/out`
error[E0463]: can't find crate for `std`                                                                                                                                             
  |                                                                                                                                                                                  
  = note: the `thumbv7em-none-eabihf` target may not be installed                                                                                                                    
                                                                                                                                                                                     
error: aborting due to previous error                                                                                                                                                
                                                                                                                                                                                     
For more information about this error, try `rustc --explain E0463`.                                                                                                                  
error: Could not compile `rust-toolchain`.                                                                                                                                           

Caused by:
  process didn't exit successfully: `rustc --crate-name rust_toolchain src/main.rs --color always --crate-type bin --emit=dep-info,link -C debuginfo=2 -C metadata=f8ada62e29834902 -C extra-filename=-f8ada62e29834902 --out-dir /tmp/test/target/thumbv7em-none-eabihf/debug/deps --target thumbv7em-none-eabihf -C incremental=/tmp/test/target/thumbv7em-none-eabihf/debug/incremental -L dependency=/tmp/test/target/thumbv7em-none-eabihf/debug/deps -L dependency=/tmp/test/target/debug/deps --extern stm32f3=/tmp/test/target/thumbv7em-none-eabihf/debug/deps/libstm32f3-89c96bc170109bc0.rlib -C link-arg=-Tlink.x -L /tmp/test/target/thumbv7em-none-eabihf/debug/build/stm32f3-7c665be50e2d2105/out -L '/home/wucke13/documents/people/Günther Kemnitz/rust-toolchain/target/thumbv7em-none-eabihf/debug/build/cortex-m-e093635255097b24/out' -L /tmp/test/target/thumbv7em-none-eabihf/debug/build/cortex-m-rt-28a646978498040b/out` (exit code: 1)

rustup show shows that the needed target is installed, though:

Default host: x86_64-unknown-linux-gnu

installed toolchains
--------------------

stable-x86_64-unknown-linux-gnu
beta-x86_64-unknown-linux-gnu (default)
nightly-x86_64-unknown-linux-gnu

installed targets for active toolchain
--------------------------------------

thumbv6m-none-eabi
thumbv7em-none-eabi
thumbv7em-none-eabihf
thumbv7m-none-eabi
x86_64-unknown-linux-gnu

active toolchain
----------------

beta-x86_64-unknown-linux-gnu (default)
rustc 1.31.0-beta.8 (9142ac95a 2018-11-10)

What causes this?

[japaric]

error[E0463]: can't find crate for std

Likely src/main.rs does not have the #![no_std] attribute in it.

[wucke13]

Thats it! Thanks!

[H-Y-B]

error[E0463]: can't find crate for std

Likely src/main.rs does not have the #![no_std] attribute in it.

But if i want to print "Hello world" by using std::println! , what should I do?

[georgio]

@H-Y-B This might answer your question :-)
https://docs.rust-embedded.org/discovery/06-hello-world/index.html

[0xAl3xH]

What if one needs to use other std libraries like std::ptr for example?

[adamgreig]

What if one needs to use other std libraries like std::ptr for example?

Everything you can use in a #[no_std] context is in core, for example: core::ptr. Many std modules are re-exported from core.

[niondir]

Is there a way to find out where std is used? I have the #![no_std] in my main.

[wucke13]

@niondir Isn't it already stated in the cargo output? Other than that, just grep for std:: in your src. Do you have any deps through Cargo.toml? Some deps have no_std as a feature, which needs to be invoked explicitly for them to be no_std conform.

[niondir]

I actually found another file where the #![no_std] was missing.