transpile: Make volatile post-increment assignment compile

Fixes #1049. Fixes #1064.

Author: GPHemsley

c2rust-transpile/src/translator/operators.rs

@@ -797,7 +797,7 @@ impl<'c> Translation<'c> {
                 };
 
                 Ok(WithStmts::new(
-                    vec![save_old_val, mk().expr_stmt(assign_stmt)],
+                    vec![save_old_val, mk().semi_stmt(assign_stmt)],
                     mk().ident_expr(val_name),
                 ))
             },

tests/ints/src/test_volatile.rs

@@ -1,13 +1,22 @@
-use crate::volatile::rust_entry3;
+use crate::volatile::{rust_entry3, rust_volatile_stuff};
 use libc::{c_int, c_uint};
 
 #[link(name = "test")]
 extern "C" {
+    fn volatile_stuff();
+
     fn entry3(_: c_uint, _: *mut c_int);
 }
 
 const BUFFER_SIZE: usize = 9;
 
+pub fn test_compiles() {
+    unsafe {
+        volatile_stuff();
+        rust_volatile_stuff();
+    }
+}
+
 pub fn test_buffer() {
     let mut buffer = [0; BUFFER_SIZE];
     let mut rust_buffer = [0; BUFFER_SIZE];

tests/ints/src/volatile.c

@@ -44,4 +44,23 @@ void entry3(const unsigned buffer_size, int buffer[])
     buffer[8] = s.buffer[3];
 }
 
+void volatile_stuff(void)
+{
+    // Non-volatile
+    int x1 = 0;
+    int x2 = x1++;
+    x2;
+
+    // https://github.com/immunant/c2rust/issues/1049
+    volatile int x3 = 0;
+    int x4 = x3++;
+    x4;
 
+    // https://github.com/immunant/c2rust/issues/1064
+    volatile int x5 = 0;
+    while (x5 < 5)
+    {
+        int x6 = x5++;
+        x6;
+    }
+}