From 627f10cd18c2d10439a2535cdabc85f211c86920 Mon Sep 17 00:00:00 2001
From: Christoffer Lerno <christoffer@aegik.com>
Date: Thu, 19 Dec 2024 20:39:23 +0100
Subject: [PATCH] Fix bug when a macro calling an extern function was called in
 another module also declaring and calling the same function. #1690

---
 releasenotes.md                        |  2 +-
 src/compiler/llvm_codegen.c            |  7 ++++++-
 test/test_suite/abi/linking_extern.c3t | 24 ++++++++++++++++++++++++
 3 files changed, 31 insertions(+), 2 deletions(-)
 create mode 100644 test/test_suite/abi/linking_extern.c3t

diff --git a/releasenotes.md b/releasenotes.md
index 390e54a68..373b3b761 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -8,7 +8,7 @@ None
 ### Fixes
 - Fix case trying to initialize a `char[*]*` from a String.
 - Fix Map & HashMap `put_all_for_create` not copying all elements, causing `init_from_map` to create incomplete copy.
-
+- Fix bug when a macro calling an extern function was called in another module also declaring and calling the same function. #1690
 ### Stdlib changes
 - Increase BitWriter.write_bits limit up to 32 bits.
 - Updates to `Slice2d`, like `get_xy` and others.
diff --git a/src/compiler/llvm_codegen.c b/src/compiler/llvm_codegen.c
index 8909afdec..d310c345a 100644
--- a/src/compiler/llvm_codegen.c
+++ b/src/compiler/llvm_codegen.c
@@ -1298,7 +1298,12 @@ LLVMValueRef llvm_get_ref(GenContext *c, Decl *decl)
 			}
 			else
 			{
-				backend_ref = decl->backend_ref = LLVMAddFunction(c->module, scratch_buffer_to_string(), type);
+				const char *name = scratch_buffer_to_string();
+				if (decl->is_extern && (backend_ref = LLVMGetNamedFunction(c->module, name)))
+				{
+					return decl->backend_ref = backend_ref;
+				}
+				backend_ref = decl->backend_ref = LLVMAddFunction(c->module, name, type);
 			}
 			llvm_append_function_attributes(c, decl);
 			llvm_set_decl_linkage(c, decl);
diff --git a/test/test_suite/abi/linking_extern.c3t b/test/test_suite/abi/linking_extern.c3t
new file mode 100644
index 000000000..231fdae30
--- /dev/null
+++ b/test/test_suite/abi/linking_extern.c3t
@@ -0,0 +1,24 @@
+// #target: macos-x64
+module abc;
+extern fn void puts(char*);
+macro void test()
+{
+	puts("b");
+}
+module test;
+import abc;
+extern fn void puts(char*);
+fn void main()
+{
+	puts("a");
+	abc::test();
+}
+
+/* #expect: test.ll
+
+define void @test.main() #0 {
+entry:
+  call void @puts(ptr @.str)
+  call void @puts(ptr @.str.1)
+  ret void
+}