CBE: fix C output after PR #11302, reenable tests

Commit 052079c99455d01312d377d72fa1b8b5c0b22aad surfaced two issues with
the generated C code:

  - renderInt128() contained a seemingly unnecessary assertion to verify
    that the high 64 bits of the number were nonzero, dating back to
    9bf1681990fe87a6b2e5fc644a89f1aece304579. I removed it.
  - renderValue() didn't have any special handling for undefined structs,
    falling back to printing "{}" which generated invalid expressions
    such as "return {}" for functions returning structs, whereas
    "return (S){}" is the correct form. I changed it accordingly.

At the same time I'm reenabling the relevant tests.

1 files changed, 5 insertions, 1 deletions

diff --git a/src/codegen/c.zig b/src/codegen/c.zig
index 84bb3a211b..38a105c172 100644
--- a/src/codegen/c.zig
+++ b/src/codegen/c.zig
@@ -433,7 +433,6 @@ pub const DeclGen = struct {
         if (is_signed) try writer.writeAll("(int128_t)");
         if (is_neg) try writer.writeByte('-');
 
-        assert(high > 0);
         try writer.print("(((uint128_t)0x{x}u<<64)", .{high});
 
         if (low > 0)
@@ -572,6 +571,11 @@ pub const DeclGen = struct {
                     64 => return writer.writeAll("(void *)0xaaaaaaaaaaaaaaaa"),
                     else => unreachable,
                 },
+                .Struct => {
+                    try writer.writeByte('(');
+                    try dg.renderTypecast(writer, ty);
+                    return writer.writeAll("){0xaa}");
+                },
                 else => {
                     // This should lower to 0xaa bytes in safe modes, and for unsafe modes should
                     // lower to leaving variables uninitialized (that might need to be implemented