From dd5b2d1b04197903489f5da9c178e17e61bb55e3 Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Sun, 16 Sep 2018 11:23:38 -0400
Subject: [PATCH] fix crash when pointer casting a runtime extern function

---
 src/analyze.cpp      | 7 ++++---
 test/cases/align.zig | 9 +++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/analyze.cpp b/src/analyze.cpp
index c9ae86539..0401c7125 100644
--- a/src/analyze.cpp
+++ b/src/analyze.cpp
@@ -3992,9 +3992,10 @@ uint32_t get_ptr_align(CodeGen *g, ZigType *type) {
         return (ptr_type->data.pointer.explicit_alignment == 0) ?
             get_abi_alignment(g, ptr_type->data.pointer.child_type) : ptr_type->data.pointer.explicit_alignment;
     } else if (ptr_type->id == ZigTypeIdFn) {
-        return (ptr_type->data.fn.fn_type_id.alignment == 0) ?
-            LLVMABIAlignmentOfType(g->target_data_ref, ptr_type->data.fn.raw_type_ref) :
-            ptr_type->data.fn.fn_type_id.alignment;
+        // I tried making this use LLVMABIAlignmentOfType but it trips this assertion in LLVM:
+        // "Cannot getTypeInfo() on a type that is unsized!"
+        // when getting the alignment of `?extern fn() void`.
+        return (ptr_type->data.fn.fn_type_id.alignment == 0) ? 1 : ptr_type->data.fn.fn_type_id.alignment;
     } else if (ptr_type->id == ZigTypeIdPromise) {
         return get_coro_frame_align_bytes(g);
     } else {
diff --git a/test/cases/align.zig b/test/cases/align.zig
index e052c3c3a..838935f53 100644
--- a/test/cases/align.zig
+++ b/test/cases/align.zig
@@ -219,3 +219,12 @@ test "alignment of structs" {
         b: *i32,
     }) == @alignOf(usize));
 }
+
+test "alignment of extern() void" {
+    var runtime_nothing = nothing;
+    const casted1 = @ptrCast(*const u8, runtime_nothing);
+    const casted2 = @ptrCast(extern fn () void, casted1);
+    casted2();
+}
+
+extern fn nothing() void {}