Having problems expanding macros with build.rs #758
Description
I encountered a problem with the expansion of macros using build.rs. Here is a minimal example to point out the problems I'm having. I have the following lib.rs.
// lib.rs file
macro_rules! number {
($name:ident, $number:expr) => {
#[no_mangle]
pub extern "C" fn $name () -> u64 {
$number
}
}
}
number!(two, 2);with the following cbindgen.toml
language = "C"
[parse.expand]
crates = ["testing"]If I run rustup run nightly cbindgen ./ --config cbindgen.toml --crate testing --output bindings.h, the macros are expanded, and I get the expected file bindings.h.
However, if I try to expand macros and build the binding using a build.rs file, the compilation takes a lot and returns an error at the end of it. The build files I've tried are the following:
// With the builder struct
extern crate cbindgen;
use std::env;
fn main() {
cbindgen::Builder::new()
.with_crate(env::var("CARGO_MANIFEST_DIR").unwrap())
.with_parse_expand(&["testing"])
.generate()
.expect("Unable to generate bindings")
.write_to_file("bindings.h");
}and
// With the generate function using the same cbindgen.toml as above
extern crate cbindgen;
fn main() {
cbindgen::generate(std::env::var("CARGO_MANIFEST_DIR").unwrap())
.expect("Unable to generate bindings")
.write_to_file("bindings.h");
}When running RUST_BACKTRACE=1 cargo build I get a ton of lines like this (not copying all because would be huge):
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\n at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:227:5\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\and the final lines of the error are
stack backtrace:
0: rust_begin_unwind
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/std/src/panicking.rs:498:5
1: core::panicking::panic_fmt
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/panicking.rs:116:14
2: core::result::unwrap_failed
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/result.rs:1690:5
3: core::result::Result<T,E>::expect
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/result.rs:975:23
4: build_script_build::main
at ./build.rs:4:5
5: core::ops::function::FnOnce::call_once
at /rustc/9d1b2106e23b1abd32fce1f17267604a5102f57a/library/core/src/ops/function.rs:227:5
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
Is this a known issue? Or am I maybe doing something wrong?
Thank you!