codegen: Support casting arbitary value-types to arrays

Also calculate a valid length for the resulting array.

This enables easier usage of common uint8[]-based buffer API.

https://bugzilla.gnome.org/show_bug.cgi?id=777194

3 files changed, 85 insertions, 3 deletions

diff --git a/codegen/valaccodebasemodule.vala b/codegen/valaccodebasemodule.vala
index e8bb29f51..b1eaf3e09 100644
--- a/codegen/valaccodebasemodule.vala
+++ b/codegen/valaccodebasemodule.vala
@@ -5171,10 +5171,29 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
 					}
 				}
 			} else if (array_type != null) {
-				// cast from non-array to array, set invalid length
-				// required by string.data, e.g.
+				CCodeExpression array_length_expr;
+
+				var sizeof_to = new CCodeFunctionCall (new CCodeIdentifier ("sizeof"));
+				sizeof_to.add_argument (new CCodeConstant (get_ccode_name (array_type.element_type)));
+				var sizeof_from = new CCodeFunctionCall (new CCodeIdentifier ("sizeof"));
+
+				var value_type = expr.inner.value_type;
+				if (value_type is ValueType) {
+					var data_type = ((ValueType) value_type).data_type;
+					sizeof_from.add_argument (new CCodeConstant (get_ccode_name (data_type)));
+					array_length_expr = new CCodeBinaryExpression (CCodeBinaryOperator.DIV, sizeof_from, sizeof_to);
+				} else if (value_type is PointerType && ((PointerType) value_type).base_type is ValueType) {
+					var data_type = ((ValueType) (((PointerType) value_type).base_type)).data_type;
+					sizeof_from.add_argument (new CCodeConstant (get_ccode_name (data_type)));
+					array_length_expr = new CCodeBinaryExpression (CCodeBinaryOperator.DIV, sizeof_from, sizeof_to);
+				} else {
+					// cast from unsupported non-array to array, set invalid length
+					// required by string.data, e.g.
+					array_length_expr = new CCodeConstant ("-1");
+				}
+
 				for (int dim = 1; dim <= array_type.rank; dim++) {
-					append_array_length (expr, new CCodeConstant ("-1"));
+					append_array_length (expr, array_length_expr);
 				}
 			}
 
@@ -5183,6 +5202,10 @@ public abstract class Vala.CCodeBaseModule : CodeGenerator {
 				expr.inner.value_type is ValueType && expr.inner.value_type.nullable) {
 				// nullable integer or float or boolean or struct or enum cast to non-nullable
 				innercexpr = new CCodeUnaryExpression (CCodeUnaryOperator.POINTER_INDIRECTION, innercexpr);
+			} else if (expr.type_reference is ArrayType
+			    && expr.inner.value_type is ValueType && !expr.inner.value_type.nullable) {
+				// integer or float or boolean or struct or enum to array cast
+				innercexpr = new CCodeUnaryExpression (CCodeUnaryOperator.ADDRESS_OF, innercexpr);
 			}
 			set_cvalue (expr, new CCodeCastExpression (innercexpr, get_ccode_name (expr.type_reference)));
 
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 76fb108b7..f824f4e4e 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -132,6 +132,7 @@ TESTS = \
 	structs/bug690380.vala \
 	structs/bug749952.vala \
 	structs/bug775761.vala \
+	structs/bug777194.vala \
 	delegates/delegates.vala \
 	delegates/bug539166.vala \
 	delegates/bug595610.vala \
diff --git a/tests/structs/bug777194.vala b/tests/structs/bug777194.vala
new file mode 100644
index 000000000..def402e35
--- /dev/null
+++ b/tests/structs/bug777194.vala
@@ -0,0 +1,58 @@
+struct Foo {
+	public int64 foo;
+	public int64 bar;
+}
+
+void bar (uint8[] a) {
+	unowned Foo[] f = (Foo[]) a;
+	assert (f[0].foo == 2LL << 62);
+	assert (f[0].bar == 2LL << 31);
+}
+
+void main () {
+	unowned uint8[] tu;
+	uint8[] to;
+
+	Foo fstack = { 2LL << 62 , 2LL << 31};
+	Foo? fheap = { 2LL << 62 , 2LL << 31};
+
+	bar ((uint8[]) &fstack);
+	tu = (uint8[]) &fstack;
+	assert (tu.length == 16);
+	bar (tu);
+	to = (uint8[]) &fstack;
+	assert (to.length == 16);
+	bar (to);
+
+	bar ((uint8[]) fstack);
+	tu = (uint8[]) fstack;
+	assert (tu.length == 16);
+	bar (tu);
+	to = (uint8[]) fstack;
+	assert (to.length == 16);
+	bar (to);
+
+	bar ((uint8[]) fheap);
+	tu = (uint8[]) fheap;
+	assert (tu.length == 16);
+	bar (tu);
+	to = (uint8[]) fheap;
+	assert (to.length == 16);
+	bar (to);
+
+	int32 i32 = 2 << 28;
+	tu = (uint8[]) i32;
+	assert (tu.length == 4);
+	tu = (uint8[]) &i32;
+	assert (tu.length == 4);
+	to = (uint8[]) i32;
+	assert (to.length == 4);
+
+	uint64 u64 = 2UL << 30;
+	tu = (uint8[]) u64;
+	assert (tu.length == 8);
+	tu = (uint8[]) &u64;
+	assert (tu.length == 8);
+	to = (uint8[]) u64;
+	assert (to.length == 8);
+}