From 52325b2b435da6e7878f639aec36685f750d98c4 Mon Sep 17 00:00:00 2001
From: "Andrey R (cooldome)" <ariabushenko@gmail.com>
Date: Thu, 5 Nov 2020 13:36:58 +0000
Subject: [PATCH] fix #12636

---
 compiler/sizealignoffsetimpl.nim |  9 +++++----
 tests/misc/tsizeof.nim           | 14 +++++++++++++-
 2 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/compiler/sizealignoffsetimpl.nim b/compiler/sizealignoffsetimpl.nim
index 2c764fe12ae72..7fae4fe8f3c1d 100644
--- a/compiler/sizealignoffsetimpl.nim
+++ b/compiler/sizealignoffsetimpl.nim
@@ -259,11 +259,12 @@ proc computeSizeAlign(conf: ConfigRef; typ: PType) =
   of tyArray:
     computeSizeAlign(conf, typ[1])
     let elemSize = typ[1].size
-    if elemSize < 0:
-      typ.size = elemSize
-      typ.align = int16(elemSize)
+    let len = lengthOrd(conf, typ[0])
+    if elemSize < 0 or len < 0:
+      typ.size = szUnknownSize
+      typ.align = szUnknownSize
     else:
-      typ.size = toInt64Checked(lengthOrd(conf, typ[0]) * int32(elemSize), szTooBigSize)
+      typ.size = toInt64Checked(len * int32(elemSize), szTooBigSize)
       typ.align = typ[1].align
 
   of tyUncheckedArray:
diff --git a/tests/misc/tsizeof.nim b/tests/misc/tsizeof.nim
index a09265667b9a0..0d96a5e04f6c9 100644
--- a/tests/misc/tsizeof.nim
+++ b/tests/misc/tsizeof.nim
@@ -361,6 +361,16 @@ testinstance:
           y: int32
       z: AnotherEnum
 
+    Stack[N: static int, T: object] = object
+      pad: array[128 - sizeof(array[N, ptr T]) - sizeof(int) - sizeof(pointer), byte]
+      stack: array[N, ptr T]
+      len*: int
+      rawMem: ptr array[N, T]
+
+    Stack2[T: object] = object
+      pad: array[128 - sizeof(array[sizeof(T), ptr T]), byte]
+    
+
   const trivialSize = sizeof(TrivialType) # needs to be able to evaluate at compile time
 
   proc main(): void =
@@ -377,6 +387,8 @@ testinstance:
     var po : PaddingOfSetEnum33
     var capo: MyCustomAlignPackedObject
     var issue15516: MyObject
+    var issue12636_1: Stack[5, MyObject]
+    var issue12636_2: Stack2[MyObject]
 
     var
       e1: Enum1
@@ -395,7 +407,7 @@ testinstance:
     else:
       doAssert sizeof(SimpleAlignment) > 10
 
-    testSizeAlignOf(t,a,b,c,d,e,f,g,ro,go,po, e1, e2, e4, e8, eoa, eob, capo, issue15516)
+    testSizeAlignOf(t,a,b,c,d,e,f,g,ro,go,po, e1, e2, e4, e8, eoa, eob, capo, issue15516, issue12636_1, issue12636_2)
 
     type
       WithBitsize {.objectconfig.} = object