Fix bug when a macro calling an extern function was called in another module also declaring and calling the same function. #1690

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.

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);

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
+}