Splat 8 arguments can sometimes cause incorrect behaviour in the compiler. #2283

releasenotes.md

@@ -39,6 +39,7 @@
 - Bit shift operation fails with inline uint enum despite matching underlying type #2279.
 - Fix to codegen when using a bitstruct constant defined using a cast with an operator #2248.
 - Function pointers are now compile time constants. 
+- Splat 8 arguments can sometimes cause incorrect behaviour in the compiler. #2283
 
 ### Stdlib changes
 - Improve contract for readline. #2280

src/compiler/sema_expr.c

@@ -6369,7 +6369,7 @@ Expr **sema_expand_vasplat_exprs(SemaContext *context, Expr **exprs)
 				}
 				Expr **new_args = sema_splat_arraylike_insert(context, exprs, inner, len, i);
 				if (!new_args) return false;
-				if (!exprs) return NULL;
+				exprs = new_args;
 				count = vec_size(exprs);
 				expand = true;
 				break;

test/test_suite/functions/splat_8.c3t

@@ -0,0 +1,33 @@
+// #target: linux-aarch64
+module test;
+import std;
+macro @do_splat_thing(#args)
+{
+	String[] args = { "program-name", ...(String[])#args };
+}
+
+fn int main()
+{
+	@do_splat_thing({ "str1","str1","str1","str1","str1","str1","str3" });
+	@do_splat_thing({ "str1","str1","str1","str1","str1","str1","str1","str2" });
+	return 0;
+}
+
+/* #expect: test.ll
+
+define i32 @main() #0 {
+entry:
+  %args = alloca %"char[][]", align 8
+  %literal = alloca [8 x %"char[]"], align 8
+  %args1 = alloca %"char[][]", align 8
+  %literal2 = alloca [9 x %"char[]"], align 8
+  call void @llvm.memcpy.p0.p0.i32(ptr align 8 %literal, ptr align 8 @.__const, i32 128, i1 false)
+  %0 = insertvalue %"char[][]" undef, ptr %literal, 0
+  %1 = insertvalue %"char[][]" %0, i64 8, 1
+  store %"char[][]" %1, ptr %args, align 8
+  call void @llvm.memcpy.p0.p0.i32(ptr align 8 %literal2, ptr align 8 @.__const.17, i32 144, i1 false)
+  %2 = insertvalue %"char[][]" undef, ptr %literal2, 0
+  %3 = insertvalue %"char[][]" %2, i64 9, 1
+  store %"char[][]" %3, ptr %args1, align 8
+  ret i32 0
+}