Libc process context (#1335)

- **Fix**
- **Fix**

.github/workflows/test.yaml

@@ -94,9 +94,9 @@ jobs:
             tags: not @library
           - name: stak-tools
           - name: mstak
-            tags: not @process-context
+            tags: not @command-line and not @environment-variable and not @library
           - name: mstak-tools
-            tags: not @process-context
+            tags: not @environment-variable
         exclude:
           - os: ${{ github.ref == 'refs/heads/main' && 'none' || 'macos-14' }}
     runs-on: ${{ matrix.os }}

cmd/minimal/interpret/Cargo.toml

@@ -16,7 +16,9 @@ stak-device = { version = "0.2.24", path = "../../../device", features = [
 ] }
 stak-file = { version = "0.4.0", path = "../../../file", features = ["libc"] }
 stak-primitive = { version = "0.5.0", path = "../../../primitive" }
-stak-process-context = { version = "0.2.0", path = "../../../process_context" }
+stak-process-context = { version = "0.2.0", path = "../../../process_context", features = [
+  "libc",
+] }
 stak-vm = { version = "0.5.0", path = "../../../vm" }
 
 [lints]

cmd/minimal/interpret/src/main.rs

@@ -14,7 +14,7 @@ use mstak_util::Mmap;
 use stak_device::libc::{ReadWriteDevice, Stderr, Stdin, Stdout};
 use stak_file::LibcFileSystem;
 use stak_primitive::SmallPrimitiveSet;
-use stak_process_context::VoidProcessContext;
+use stak_process_context::LibcProcessContext;
 use stak_vm::{Value, Vm};
 
 const HEAP_SIZE: usize = 1 << 19;
@@ -41,7 +41,7 @@ unsafe extern "C" fn main(argc: isize, argv: *const *const i8) -> isize {
         SmallPrimitiveSet::new(
             ReadWriteDevice::new(Stdin::new(), Stdout::new(), Stderr::new()),
             LibcFileSystem::new(),
-            VoidProcessContext::new(),
+            LibcProcessContext::new(argc, argv),
         ),
     )
     .unwrap();

features/process-context/command-line.feature

@@ -1,4 +1,4 @@
-@process-context
+@command-line
 Feature: Command line
   Scenario: Get an argument
     Given a file named "main.scm" with:

features/process-context/environment-variable.feature

@@ -1,4 +1,4 @@
-@process-context
+@environment-variable
 Feature: Environment variables
   Scenario: Get an environment variable
     Given a file named "main.scm" with:

process_context/Cargo.toml

@@ -9,6 +9,7 @@ readme.workspace = true
 repository.workspace = true
 
 [features]
+libc = []
 std = ["dep:once_cell"]
 
 [dependencies]

process_context/src/lib.rs

@@ -8,11 +8,15 @@ extern crate alloc;
 #[cfg(feature = "std")]
 extern crate std;
 
+#[cfg(feature = "libc")]
+mod libc;
 #[cfg(feature = "std")]
 mod os;
 mod process_context;
 mod void;
 
+#[cfg(feature = "libc")]
+pub use libc::LibcProcessContext;
 #[cfg(feature = "std")]
 pub use os::OsProcessContext;
 pub use process_context::ProcessContext;

process_context/src/libc.rs

@@ -0,0 +1,35 @@
+use crate::ProcessContext;
+use core::{ffi::CStr, slice};
+
+/// A process context based on libc.
+#[derive(Debug)]
+pub struct LibcProcessContext {
+    arguments: &'static [*const i8],
+}
+
+impl LibcProcessContext {
+    /// Creates a process context.
+    ///
+    /// # Safety
+    ///
+    /// The `argc` and `argv` arguments should be the ones passed down as
+    /// arguments to the `main` function in C.
+    pub const unsafe fn new(argc: isize, argv: *const *const i8) -> Self {
+        Self {
+            arguments: unsafe { slice::from_raw_parts(argv, argc as _) },
+        }
+    }
+}
+
+impl ProcessContext for LibcProcessContext {
+    fn command_line_rev(&self) -> impl IntoIterator<Item = &str> {
+        self.arguments
+            .iter()
+            .rev()
+            .map(|&argument| unsafe { CStr::from_ptr(argument) }.to_str().unwrap())
+    }
+
+    fn environment_variables(&self) -> impl IntoIterator<Item = (&str, &str)> {
+        []
+    }
+}