rustdoc will execute unreachable macros

[bf]

I tried this code:

fn private_no_docs() { 
  let nobody_ever_use_this = include_str!("/etc/passwd-FILE_DOES_NOT_EXIST");
}

fn main() {}

I expected to see this happen: Nothing, because rustdoc is just taking the documentation comments and creates a HTML document from it.

Instead, this happened:

The include_str! macro is executed by rustdoc even though it is in unreachable code.
The macro tries to load a non-existing file and compilation stops.
rustdoc would be expected to not run this macro.

This also happens with cargo doc

 $ cargo doc
 Documenting evildependency v0.1.0 (./cargo-rustdoc/evildependency)
    Checking evildependency v0.1.0 (./cargo-rustdoc/evildependency)
error: couldn't read `/etc/passwd-FILE_DOES_NOT_EXIST`: No such file or directory (os error 2)
 --> ./cargo-rustdoc/evildependency/src/lib.rs:8:31
  |
8 |   let nobody_ever_uses_this = include_str!("/etc/passwd-FILE_DOES_NOT_EXIST");
  |                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: this error originates in the macro `include_str` (in Nightly builds, run with -Z macro-backtrace for more info)

error: could not document `evildependency`
warning: build failed, waiting for other jobs to finish...
error: could not compile `evildependency` (lib) due to 1 previous error

Meta

rustc --version --verbose:

rustc 1.83.0 (90b35a623 2024-11-26) (Arch Linux rust 1:1.83.0-1)
binary: rustc
commit-hash: 90b35a6239c3d8bdabc530a6a0816f7ff89a0aaf
commit-date: 2024-11-26
host: x86_64-unknown-linux-gnu
release: 1.83.0
LLVM version: 18.1.8

[jieyouxu]

Triage: this is not rustdoc, this is rustc. EDIT: I see what you mean, it's both because rustdoc uses some parts of rustc. Tagging as C-discussion, T-rustdoc can mark this as C-bug if they consider this something they want to handle.

cc @rust-lang/security

[Noratrieb]

rustdoc needs to expand all macros to be able to generate documentation properly. for example, this macro could expand to an impl block, which would need to be documented.

[bf]

The function is private, I thought rustdoc will not document private functions? How can impl block break out of the scope?