tests: add test for symbol length

tests/symbol_length.rs

@@ -0,0 +1,61 @@
+#![cfg(all(unix, not(miri)))]
+
+use std::io::{Error, Result, Write};
+
+use pin_init::*;
+
+#[pin_data]
+pub struct Test {}
+
+pub fn init() -> impl PinInit<Test, Error> {
+    pin_init!(Test {} ? Error)
+}
+
+fn init_fn_ptr<T, E, I: PinInit<T, E>>(_: &I) -> *mut () {
+    I::__pinned_init as *mut ()
+}
+
+fn read_symbols() -> Result<Vec<String>> {
+    let path = std::env::current_exe()?;
+    let output = std::process::Command::new("nm")
+        .arg(path)
+        .arg("--just-symbols")
+        .output()?;
+    if !output.status.success() {
+        Err(Error::other("exit code is not 0"))?
+    }
+    let symbols = String::from_utf8_lossy(&output.stdout);
+    Ok(symbols
+        .lines()
+        .filter(|x| !x.is_empty())
+        .map(|x| x.to_owned())
+        .collect())
+}
+
+#[test]
+fn type_name() {
+    let init = init();
+    let init_fn = init_fn_ptr(&init);
+    std::hint::black_box(init_fn);
+
+    let mut symbols = match read_symbols() {
+        Ok(v) => v,
+        Err(err) => {
+            // This might be some setup issue (e.g. no nm installed).
+            // Instead of failing the test, print the error and continue.
+            // Do not use `eprintln!()` as it would be captured.
+            writeln!(std::io::stderr(), "cannot read symbols {:?}", err).unwrap();
+            return;
+        }
+    };
+
+    // Filter out non-related symbols.
+    symbols.retain(|x| x.contains("pin_init") && !x.contains("map"));
+
+    // Find the longest symbol
+    symbols.sort_by_key(|x| x.len().wrapping_neg());
+    let symbol = &symbols[0];
+    println!("{}: {}", symbol.len(), symbol);
+
+    assert!(symbol.len() < 180);
+}