Make the unwinding dependency conditional on panic = "unwind".

c-scape/Cargo.toml

@@ -46,7 +46,7 @@ alloc = { version = "1.0.0", optional = true, package = "rustc-std-workspace-all
 # TODO: Eventually, we should propose a `fde-phdr-rustix` backend option to
 # upstream `unwinding` so that it doesn't need to go through `dl_iterate_phdr`,
 # but `fde-phdr-dl` works for now.
-[target.'cfg(not(target_arch = "arm"))'.dependencies.unwinding]
+[target.'cfg(all(panic = "unwind", not(target_arch = "arm")))'.dependencies.unwinding]
 version = "0.2.3"
 default-features = false
 features = [

example-crates/c-gull-example-panic-abort/.gitignore

@@ -0,0 +1,2 @@
+/target
+Cargo.lock

example-crates/c-gull-example-panic-abort/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "c-gull-example-panic-abort"
+version = "0.0.0"
+edition = "2021"
+publish = false
+
+[dependencies.libc]
+path = "../../c-gull"
+default-features = false
+features = [
+    "take-charge",
+    "std",
+    "thread",
+    "call-main",
+    "malloc-via-crates",
+    "threadsafe-setenv"
+]
+package = "c-gull"
+
+[profile.dev]
+panic = "abort"
+[profile.release]
+panic = "abort"
+
+# This is just an example crate, and not part of the c-ward workspace.
+[workspace]

example-crates/c-gull-example-panic-abort/README.md

@@ -0,0 +1,3 @@
+Like the [c-gull-example example], but uses panic=abort in Cargo.toml.
+
+[c-gull-example example]: https://github.com/sunfishcode/c-ward/blob/main/example-crates/c-gull-example/README.md

example-crates/c-gull-example-panic-abort/build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // Pass -nostartfiles to the linker.
+    println!("cargo:rustc-link-arg=-nostartfiles");
+}

example-crates/c-gull-example-panic-abort/src/main.rs

@@ -0,0 +1,8 @@
+//! A simple example using "take-charge" mode.
+
+fn main() {
+    println!("Hello world using Rust `println!`!");
+    unsafe {
+        libc::printf("Hello world using libc `printf`!\n\0".as_ptr().cast());
+    }
+}

example-crates/c-gull-unwinding/.gitignore

@@ -0,0 +1,2 @@
+/target
+Cargo.lock

example-crates/c-gull-unwinding/Cargo.toml

@@ -0,0 +1,21 @@
+[package]
+name = "c-gull-unwinding"
+version = "0.0.0"
+edition = "2021"
+publish = false
+
+[dependencies.libc]
+path = "../../c-gull"
+default-features = false
+features = [
+    "take-charge",
+    "std",
+    "thread",
+    "call-main",
+    "malloc-via-crates",
+    "threadsafe-setenv"
+]
+package = "c-gull"
+
+# This is just an example crate, and not part of the c-ward workspace.
+[workspace]

example-crates/c-gull-unwinding/README.md

@@ -0,0 +1,6 @@
+This crate demonstrates the use of c-gull in "take-charge" mode, and includes
+unwinding panic support.
+
+It's the same as [c-gull-example], but it performs an unwind.
+
+[c-gull-example]: https://github.com/sunfishcode/c-ward/tree/main/example-crates/c-gull-example#readme

example-crates/c-gull-unwinding/build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // Pass -nostartfiles to the linker.
+    println!("cargo:rustc-link-arg=-nostartfiles");
+}

example-crates/c-gull-unwinding/src/main.rs

@@ -0,0 +1,19 @@
+//! A simple example using `std::panic::catch_unwind`.
+
+fn main() {
+    // Panic and catch it.
+    std::panic::catch_unwind(|| call_do_panic()).unwrap_err();
+
+    println!("Hello, world!");
+    unsafe {
+        libc::printf("Hello world using libc `printf`!\n\0".as_ptr().cast());
+    }
+}
+
+fn call_do_panic() {
+    do_panic()
+}
+
+fn do_panic() {
+    panic!("catch me!");
+}

example-crates/c-scape-example-panic-abort/.gitignore

@@ -0,0 +1,2 @@
+/target
+Cargo.lock

example-crates/c-scape-example-panic-abort/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "c-scape-example"
+version = "0.0.0"
+edition = "2021"
+publish = false
+
+[dependencies.libc]
+path = "../../c-scape"
+# Disable the default features, and enable "take-charge" mode.
+default-features = false
+features = [
+    "take-charge",
+    "thread",
+    "call-main",
+    "malloc-via-rust-global-alloc",
+    "threadsafe-setenv",
+    # This simple example will never unwind.
+    "eh-personality-continue",
+    # This simple example will never panic.
+    "panic-handler-trap",
+    "global-allocator",
+]
+package = "c-scape"
+
+[dependencies]
+errno = { version = "0.3.3", default-features = false }
+
+[profile.dev]
+panic = "abort"
+[profile.release]
+panic = "abort"
+
+# This is just an example crate, and not part of the c-ward workspace.
+[workspace]

example-crates/c-scape-example-panic-abort/README.md

@@ -0,0 +1,3 @@
+Like the [c-scape-example example], but uses panic=abort in Cargo.toml.
+
+[c-scape-example example]: https://github.com/sunfishcode/c-ward/blob/main/example-crates/c-scape-example/README.md

example-crates/c-scape-example-panic-abort/build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    // Pass -nostartfiles to the linker.
+    println!("cargo:rustc-link-arg=-nostartfiles");
+}

example-crates/c-scape-example-panic-abort/src/main.rs

@@ -0,0 +1,22 @@
+//! A simple example using `no_main`, `no_std`, and "take-charge" mode.
+
+#![no_std]
+#![no_main]
+
+#[no_mangle]
+unsafe extern "C" fn main(_argc: i32, _argv: *const *const u8, _envp: *const *const u8) -> i32 {
+    // Call functions declared in the `libc` crate, which will be resolved by
+    // c-scape. c-scape doesn't have `printf`, so we do it by hand.
+    let message = b"Hello, world!\n";
+    let mut remaining = &message[..];
+    while !remaining.is_empty() {
+        match libc::write(libc::STDOUT_FILENO, message.as_ptr().cast(), message.len()) {
+            -1 => match errno::errno().0 {
+                libc::EINTR => continue,
+                _ => panic!(),
+            },
+            n => remaining = &remaining[n as usize..],
+        }
+    }
+    libc::exit(0);
+}

example-crates/c-scape-unwinding/README.md

@@ -3,6 +3,6 @@ and `no_std`, and includes unwinding panic support.
 
 It's the same as [c-scape-example], but enables the "eh-personality" and
 "panic-handler" features instead of defining stub `#[panic_handler]` and
-`#[lang = "eh_personality"]` functions, and performs an unwind.
+`#[lang = "eh_personality"]` functions, and it performs an unwind.
 
 [c-scape-example]: https://github.com/sunfishcode/c-ward/tree/main/example-crates/c-scape-example#readme

tests/example_crates.rs

@@ -73,6 +73,18 @@ fn example_crate_c_gull_example() {
     );
 }
 
+#[test]
+fn example_crate_c_gull_example_panic_abort() {
+    test_crate(
+        "c-gull-example-panic-abort",
+        &[],
+        &[],
+        "Hello world using Rust `println!`!\nHello world using libc `printf`!\n",
+        "",
+        None,
+    );
+}
+
 #[test]
 fn example_crate_c_gull_lto() {
     test_crate(
@@ -102,6 +114,18 @@ fn example_crate_c_scape_example() {
     test_crate("c-scape-example", &[], &[], "Hello, world!\n", "", None);
 }
 
+#[test]
+fn example_crate_c_scape_example_panic_abort() {
+    test_crate(
+        "c-scape-example-panic-abort",
+        &[],
+        &[],
+        "Hello, world!\n",
+        "",
+        None,
+    );
+}
+
 #[test]
 fn example_crate_c_scape_unwinding() {
     test_crate(
@@ -114,6 +138,18 @@ fn example_crate_c_scape_unwinding() {
     );
 }
 
+#[test]
+fn example_crate_c_gull_unwinding() {
+    test_crate(
+        "c-gull-unwinding",
+        &[],
+        &[("RUST_BACKTRACE", "0")],
+        "Hello, world!\nHello world using libc `printf`!\n",
+        "thread 'main' panicked at src/main.rs:18:5:\ncatch me!\nnote: run with `RUST_BACKTRACE=1` environment variable to display a backtrace\n",
+        None,
+    );
+}
+
 #[test]
 fn example_crate_dns() {
     test_crate(