From e1ed34627f0f99e580e3e20d5782f582a08c887e Mon Sep 17 00:00:00 2001
From: Yuriy Glukhov <yglukhov@users.noreply.github.com>
Date: Sun, 19 Nov 2017 03:32:39 +0200
Subject: [PATCH] Fixes #5979 (#5980)

---
 compiler/ccgexprs.nim | 10 ++++++++--
 tests/cpp/tcasts.nim  | 10 ++++++++++
 2 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 tests/cpp/tcasts.nim

diff --git a/compiler/ccgexprs.nim b/compiler/ccgexprs.nim
index 45b2be558..9db136ed1 100644
--- a/compiler/ccgexprs.nim
+++ b/compiler/ccgexprs.nim
@@ -1645,8 +1645,14 @@ proc genSomeCast(p: BProc, e: PNode, d: var TLoc) =
     putIntoDest(p, d, e, "(($1) ($2))" %
         [getClosureType(p.module, etyp, clHalfWithEnv), rdCharLoc(a)], a.storage)
   else:
-    putIntoDest(p, d, e, "(($1) ($2))" %
-        [getTypeDesc(p.module, e.typ), rdCharLoc(a)], a.storage)
+    let srcTyp = skipTypes(e.sons[1].typ, abstractRange)
+    # C++ does not like direct casts from pointer to shorter integral types
+    if srcTyp.kind in {tyPtr, tyPointer} and etyp.kind in IntegralTypes:
+      putIntoDest(p, d, e, "(($1) (ptrdiff_t) ($2))" %
+          [getTypeDesc(p.module, e.typ), rdCharLoc(a)], a.storage)
+    else:
+      putIntoDest(p, d, e, "(($1) ($2))" %
+          [getTypeDesc(p.module, e.typ), rdCharLoc(a)], a.storage)
 
 proc genCast(p: BProc, e: PNode, d: var TLoc) =
   const ValueTypes = {tyFloat..tyFloat128, tyTuple, tyObject, tyArray}
diff --git a/tests/cpp/tcasts.nim b/tests/cpp/tcasts.nim
new file mode 100644
index 000000000..35f06234d
--- /dev/null
+++ b/tests/cpp/tcasts.nim
@@ -0,0 +1,10 @@
+discard """
+  cmd: "nim cpp $file"
+  output: ""
+"""
+
+block: #5979
+  var a = 'a'
+  var p: pointer = cast[pointer](a)
+  var c = cast[char](p)
+  doAssert(c == 'a')