emit zeroed arrays as [0; N]

an array like `int x[16] = {}` was emitted as `[0, 0, 0, 0, ...]`,
but is not emitted as `[0; 16]`.

Author: folkertdev

c2rust-transpile/src/translator/literals.rs

@@ -190,6 +190,14 @@ impl<'c> Translation<'c> {
                 if is_string {
                     let v = ids.first().unwrap();
                     self.convert_expr(ctx.used(), *v)
+                } else if ids.len() == 0 {
+                    // this was likely a C array of the form `int x[16] = {}`,
+                    // we'll emit that as [0; 16].
+                    let len = mk().lit_expr(mk().int_unsuffixed_lit(n as u128));
+                    self.implicit_default_expr(ty, ctx.is_static)?
+                        .and_then(|default_value| {
+                            Ok(WithStmts::new_val(mk().repeat_expr(default_value, len)))
+                        })
                 } else {
                     Ok(ids
                         .iter()

tests/arrays/src/arrays.c

@@ -6,9 +6,14 @@ static char *foo = "mystring";
 void entry(const unsigned buffer_size, int buffer[const])
 {
     int arr[1][1] = { 1 };
-
     arr[0][0] += 9;
 
+    int arr2[16] = {};
+    arr2[15] += 9;
+
+    struct {char* x; int y;} arr3[1] = {};
+    arr3[0].y += 9;
+
     int i = 0;
 
     char abc[] = "abc";