fixes #19101; zero initialization union casts (#22185)

* zero initialization union casts

* cleans up and adds a test case for #19101

* uses nimZeroMem

1 files changed, 26 insertions, 0 deletions

diff --git a/tests/stdlib/tcasts.nim b/tests/stdlib/tcasts.nim
new file mode 100644
index 000000000..e01c7e940
--- /dev/null
+++ b/tests/stdlib/tcasts.nim
@@ -0,0 +1,26 @@
+import std/[strutils]
+import std/[assertions, objectdollar]
+
+# bug #19101
+type
+  Small = object
+    a: int
+
+  Big = object
+    a, b, c, d: int
+
+proc main =
+  var
+    n = 1'i8
+    f = 2.0
+    s = Small(a: 1)
+    b = Big(a: 12345, b: 23456, c: 34567, d: 45678)
+
+  doAssert $cast[int](f).toBin(64) == "0100000000000000000000000000000000000000000000000000000000000000"
+  f = cast[float](n)
+  doAssert $cast[int](f).toBin(64) == "0000000000000000000000000000000000000000000000000000000000000001"
+
+  doAssert $b == "(a: 12345, b: 23456, c: 34567, d: 45678)"
+  b = cast[Big](s)
+  doAssert $b == "(a: 1, b: 0, c: 0, d: 0)"
+main()