Sanitizer runtimes produce symbol confilcts or leave undefined symbols

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1

According to the rust documentation, build.rustflags should be used to pass a flag to every compiler process, even the dependencies. So we can use it to apply a sanitizer that requires a runtime (e.g., -Zsanitizer=address). Then I add to the cargo project folder a .cargo/config file, which only contains:

[build]
rustflags = ["-Zsanitizer=address"]

If I do it in a clean project (cargo new test), the compilation process works (cargo build --release). But the compilation fails as soon as I add proc-macro-error (1.0.4) as a dependency (through Cargo.toml). The error happens when trying to compile proc-macro-error, after successfully compiling all its dependencies.
Generally, I observe that this happens to whatever rlib dependency that at it's time depends on a proc-macro. I don't know if there's an additional constraint, but I discuss the dependency tree below.

With the current nightly rust compiler (1.71.0) it gives the next error:

error[E0519]: the current crate is indistinguishable from one of its dependencies: it has the same crate-name `proc_macro_error_attr` and was compiled with the same `-C metadata` arguments. This will result in symbol conflicts between the two.
   --> ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro-error-1.0.4/src/lib.rs:284:9
    |
284 | pub use proc_macro_error_attr::proc_macro_error;
    |         ^^^^^^^^^^^^^^^^^^^^^

But if I build rustc myself the nightly version of the repository (tag 1.69.0 in the repository) and add rustc = "BUILD_DIR_BIN/rustc" to the aforementioned .cargo/config, I get a different error over the same source line, telling about the sanitizer runtime symbol not being defined:

error: .../test/target/release/deps/libproc_macro_error_attr-363b79ca82bc726b.so: undefined symbol: __asan_option_detect_stack_use_after_return
   --> ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/proc-macro-error-1.0.4/src/lib.rs:284:9
    |
284 | pub use proc_macro_error_attr::proc_macro_error;
    |         ^^^^^^^^^^^^^^^^^^^^^

For reference, if I run cargo tree I get the next output:

test v0.1.0 (.../test)
└── proc-macro-error v1.0.4
    ├── proc-macro-error-attr v1.0.4 (proc-macro)
    │   ├── proc-macro2 v1.0.56
    │   │   └── unicode-ident v1.0.8
    │   └── quote v1.0.26
    │       └── proc-macro2 v1.0.56 (*)
    │   [build-dependencies]
    │   └── version_check v0.9.4
    ├── proc-macro2 v1.0.56 (*)
    ├── quote v1.0.26 (*)
    └── syn v1.0.109
        ├── proc-macro2 v1.0.56 (*)
        └── unicode-ident v1.0.8
    [build-dependencies]
    └── version_check v0.9.4

The crate types are:

  • bin for test
  • proc-macro for proc-macro-aror-attr
  • rlib for unicode-ident and proc-macro2

If I use any other sanitizer, I get the missing symbol problem for another runtime (e.g., __tsan_read8 for thread sanitizer). The reason I add the custom flags and compiler over .cargo/config is because the build.rustflags aren't used if this is done over Cargo.toml. Still, when calling cargo build and adding the --config flag with the paramenters mentioned, I reproduce the same behavior as with .cargo/config.

When looking more in detail (by using verbose output of cargo), the exact same proc-macro2 is compiled twice but with different output directories (due to metadata) and optimization (it adds -C opt-level=3 to one of those instances).

This behavior doesn't sound right to me, let me know if I'm doing something wrong or is the expected to be like that. I haven't found any information regarding a similar issue, so I consider this to not have been discussed before. I'm happy to discuss and potentially fix the problem, but I would need to hear from someone more experienced about the root cause. Should I post this on the github issues or internals discourse?

2

Using the cargo flag --target ${RUSTC_TARGET} I'm able to don't raise those errors. But when looking at the verbose output from cargo, not all the rustc commands have the rustflags specified in .cargo/config. What's the criteria to use a one target directory or another and therefore the specified flags (target/release vs target/${RUST_TARGET}/release?

3

Build scripts and proc macros that need to be build for the host will end up in target/release, while crates that end up in the final compilation output will end up in target/$TARGET/release.

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4

Still, I find that cargo invokes rustc without those arguments for certain lib crate types (e.g., quote and unidoce-ident), it is because they are dependencies of a proc-macro crate type? There are indeed 2 code invokations for unicode-ident (each going in a different target directory) and only one for quote.

But I have kind of basic question, does then all the dependency of the proc-macro crate type miss the sanitization? In this case proc-macro-error will use functions of their dependencies, or it is limited to do so?

5

Procedural macros run at build time anyway, their code isn't present in the final sanitized binary at all.

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