From cb006dd715aa5f66d06d42ef78f0b89a15f3e661 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Sun, 31 Aug 2025 23:18:27 +0200
Subject: [PATCH] - Compiler module-scope pointer to slice with offset, causes
 assert. #2446

---
 releasenotes.md                          |  1 +
 src/compiler/llvm_codegen_expr.c         | 20 ++++++++++++++++---
 test/test_suite/globals/global_slice.c3t | 25 ++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 3 deletions(-)
 create mode 100644 test/test_suite/globals/global_slice.c3t

diff --git a/releasenotes.md b/releasenotes.md
index af4ab6201..2ef2c3b96 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -89,6 +89,7 @@
 - Enum inference, like `Foo x = $eval("A")`, now works correctly for `$eval`.
 - Fix regression where files were added more than once. #2442
 - Disambiguate types when they have the same name and need cast between each other.
+- Compiler module-scope pointer to slice with offset, causes assert. #2446
 
 ### Stdlib changes
 - Add `==` to `Pair`, `Triple` and TzDateTime. Add print to `Pair` and `Triple`.
diff --git a/src/compiler/llvm_codegen_expr.c b/src/compiler/llvm_codegen_expr.c
index ee40c7423..d0e7774f0 100644
--- a/src/compiler/llvm_codegen_expr.c
+++ b/src/compiler/llvm_codegen_expr.c
@@ -721,11 +721,19 @@ static inline void llvm_emit_subscript_addr(GenContext *c, BEValue *value, Expr
 	bool start_from_end = expr->subscript_expr.index.start_from_end;
 	if (parent_type_kind == TYPE_SLICE)
 	{
-		needs_len = safe_mode_enabled() || start_from_end;
+		needs_len = (safe_mode_enabled() && !llvm_is_global_eval(c)) || start_from_end;
 		if (needs_len)
 		{
-			llvm_emit_slice_len(c, value, &len);
-			llvm_value_rvalue(c, &len);
+			if (LLVMIsAGlobalVariable(value->value))
+			{
+				llvm_value_set(&len, LLVMGetInitializer(value->value), parent_type);
+				llvm_emit_slice_len(c, &len, &len);
+			}
+			else
+			{
+				llvm_emit_slice_len(c, value, &len);
+				llvm_value_rvalue(c, &len);
+			}
 		}
 	}
 	else if (parent_type_kind == TYPE_ARRAY || parent_type_kind == TYPE_VECTOR)
@@ -5080,11 +5088,17 @@ void llvm_emit_slice_pointer(GenContext *c, BEValue *slice, BEValue *pointer)
 	llvm_value_fold_optional(c, slice);
 	if (slice->kind == BE_ADDRESS)
 	{
+		if (LLVMIsAGlobalVariable(slice->value))
+		{
+			llvm_value_set(slice, LLVMGetInitializer(slice->value), slice->type);
+			goto NEXT;
+		}
 		AlignSize alignment;
 		LLVMValueRef ptr = llvm_emit_struct_gep_raw(c, slice->value, llvm_get_type(c, slice->type), 0, slice->alignment, &alignment);
 		llvm_value_set_address(c, pointer, ptr, ptr_type, alignment);
 		return;
 	}
+NEXT:;
 	LLVMValueRef ptr = llvm_emit_extract_value(c, slice->value, 0);
 	llvm_value_set(pointer, ptr, ptr_type);
 }
diff --git a/test/test_suite/globals/global_slice.c3t b/test/test_suite/globals/global_slice.c3t
new file mode 100644
index 000000000..850539d26
--- /dev/null
+++ b/test/test_suite/globals/global_slice.c3t
@@ -0,0 +1,25 @@
+module other_module;
+int[] list_of_ints = { 1, 2, 3 };
+int* ref_to_2nd = &list_of_ints[^1];
+
+module somemain;
+import other_module, std;
+fn void main() => @pool()
+{
+    io::printfn("ptr %p", other_module::ref_to_2nd);
+    *other_module::ref_to_2nd = 42;
+    io::printfn("%s", other_module::list_of_ints);
+}
+
+/* #expect: other_module.ll
+
+; ModuleID = 'other_module'
+source_filename = "other_module"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "aarch64-apple-macosx11.0.0"
+
+%"int[]" = type { ptr, i64 }
+
+@.__const_slice = private unnamed_addr global [3 x i32] [i32 1, i32 2, i32 3], align 4
+@other_module.list_of_ints = local_unnamed_addr global %"int[]" { ptr @.__const_slice, i64 3 }, align 8
+@other_module.ref_to_2nd = local_unnamed_addr global ptr getelementptr inbounds (i8, ptr @.__const_slice, i64 8), align 8