fix assertion when taking slice of zero-length array

closes #788
ziglang · Mar 6, 2018 · 44ae891 · 44ae891
1 parent cc0f660
commit 44ae891
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Showing 2 changed files with 15 additions and 1 deletion.
diff --git a/src/ir.cpp b/src/ir.cpp
@@ -15821,9 +15821,13 @@ static TypeTableEntry *ir_analyze_instruction_slice(IrAnalyze *ira, IrInstructio
     TypeTableEntry *return_type;
 
     if (array_type->id == TypeTableEntryIdArray) {
+        uint32_t byte_alignment = ptr_type->data.pointer.alignment;
+        if (array_type->data.array.len == 0 && byte_alignment == 0) {
+            byte_alignment = get_abi_alignment(ira->codegen, array_type->data.array.child_type);
+        }
         TypeTableEntry *slice_ptr_type = get_pointer_to_type_extra(ira->codegen, array_type->data.array.child_type,
             ptr_type->data.pointer.is_const, ptr_type->data.pointer.is_volatile,
-            ptr_type->data.pointer.alignment, 0, 0);
+            byte_alignment, 0, 0);
         return_type = get_slice_type(ira->codegen, slice_ptr_type);
     } else if (array_type->id == TypeTableEntryIdPointer) {
         TypeTableEntry *slice_ptr_type = get_pointer_to_type_extra(ira->codegen, array_type->data.pointer.child_type,

diff --git a/test/cases/misc.zig b/test/cases/misc.zig
@@ -650,3 +650,13 @@ test "packed struct, enum, union parameters in extern function" {
 
 export fn testPackedStuff(a: &const PackedStruct, b: &const PackedUnion, c: PackedEnum) void {
 }
+
+
+test "slicing zero length array" {
+    const s1 = ""[0..];
+    const s2 = ([]u32{})[0..];
+    assert(s1.len == 0);
+    assert(s2.len == 0);
+    assert(mem.eql(u8, s1, ""));
+    assert(mem.eql(u32, s2, []u32{}));
+}