From 940e02ea928f36e90c8cb4cc2665ea5f31d9217d Mon Sep 17 00:00:00 2001
From: Martin Kinkelin <mkinkelin@symmetryinvestments.com>
Date: Sat, 5 Aug 2023 13:38:39 +0200
Subject: [PATCH] Make size_t/ptrdiff_t match pointer size on 8/16 bit
 architectures

---
 dmd/mtype.d                     | 28 ++++++++++++++++++++++++++++
 dmd/typesem.d                   | 12 ++++++++++++
 tests/compilable/size_t_16bit.d | 13 +++++++++++++
 3 files changed, 53 insertions(+)
 create mode 100644 tests/compilable/size_t_16bit.d

diff --git a/dmd/mtype.d b/dmd/mtype.d
index 9b210528f7d..cf1e58fde29 100644
--- a/dmd/mtype.d
+++ b/dmd/mtype.d
@@ -892,10 +892,38 @@ version (IN_LLVM)
         twstring = twchar.immutableOf().arrayOf();
         tdstring = tdchar.immutableOf().arrayOf();
 
+version (IN_LLVM)
+{
+        switch (target.ptrsize)
+        {
+            case 1:
+                tsize_t    = basic[Tuns8];
+                tptrdiff_t = basic[Tint8];
+                break;
+            case 2:
+                tsize_t    = basic[Tuns16];
+                tptrdiff_t = basic[Tint16];
+                break;
+            case 4:
+                tsize_t    = basic[Tuns32];
+                tptrdiff_t = basic[Tint32];
+                break;
+            case 8:
+                tsize_t    = basic[Tuns64];
+                tptrdiff_t = basic[Tint64];
+                break;
+            default:
+                assert(0, "Unsupported target pointer size");
+        }
+}
+else
+{
         const isLP64 = target.isLP64;
 
         tsize_t    = basic[isLP64 ? Tuns64 : Tuns32];
         tptrdiff_t = basic[isLP64 ? Tint64 : Tint32];
+}
+
         thash_t = tsize_t;
     }
 
diff --git a/dmd/typesem.d b/dmd/typesem.d
index f0decf2a48d..456c08ec84f 100644
--- a/dmd/typesem.d
+++ b/dmd/typesem.d
@@ -1071,6 +1071,18 @@ extern(C++) Type typeSemantic(Type type, const ref Loc loc, Scope* sc)
             }
             else
             {
+version (IN_LLVM)
+{
+                // Kludge for 8/16 bit targets and `__LINE__` default arguments of type int:
+                // insert hidden cast if the parameter type is size_t.
+                // Without this, importing object.d fails (Exception constructors taking size_t line numbers).
+                if (e.isLineInitExp() && target.ptrsize < 4 && fparam.type.equivalent(Type.tsize_t))
+                {
+                    if (!e.type)
+                        e.type = Type.tint32;
+                    e = e.castTo(sc, fparam.type);
+                }
+}
                 e = inferType(e, fparam.type);
                 Initializer iz = new ExpInitializer(e.loc, e);
                 iz = iz.initializerSemantic(sc, fparam.type, INITnointerpret);
diff --git a/tests/compilable/size_t_16bit.d b/tests/compilable/size_t_16bit.d
new file mode 100644
index 00000000000..53e8681e63f
--- /dev/null
+++ b/tests/compilable/size_t_16bit.d
@@ -0,0 +1,13 @@
+// A minimal test wrt. size_t on a 16-bit architecture.
+
+// REQUIRES: target_AVR
+// RUN: %ldc -mtriple=avr -betterC -c %s
+
+static assert(size_t.sizeof == 2);
+static assert(ptrdiff_t.sizeof == 2);
+
+// test bounds checks
+int foo(int[] arr)
+{
+    return arr[1];
+}