add test to ensure CAPI can be consumed by pure C code

CMakeLists.txt

@@ -99,7 +99,7 @@ add_compile_options(
   -Wextra
   -Wno-unused-parameter
   -Wshadow
-  -Wnon-virtual-dtor
+  $<$<COMPILE_LANGUAGE:CXX>:-Wnon-virtual-dtor>
   -pedantic
   -fno-omit-frame-pointer)
 

include/llzk-c/Support.h

@@ -120,7 +120,7 @@ typedef struct LlzkAffineMapOperandsBuilder {
 } LlzkAffineMapOperandsBuilder;
 
 /// Creates a new struct. The owner is responsible for cleaning the struct.
-MLIR_CAPI_EXPORTED LlzkAffineMapOperandsBuilder llzkAffineMapOperandsBuilderCreate();
+MLIR_CAPI_EXPORTED LlzkAffineMapOperandsBuilder llzkAffineMapOperandsBuilderCreate(void);
 
 /// Destroys the struct releasing its resources.
 MLIR_CAPI_EXPORTED void llzkAffineMapOperandsBuilderDestroy(LlzkAffineMapOperandsBuilder *builder);

unittests/CAPI/CMakeLists.txt

@@ -1,3 +1,17 @@
+# C compatibility test - verifies the C API can be consumed from pure C code
+# This test is run separately in CI, not as part of the main unit tests suite
+add_executable(LLZK_CAPI_C_Test c_compatibility_test.c)
+set_target_properties(LLZK_CAPI_C_Test PROPERTIES LINKER_LANGUAGE CXX)
+target_link_libraries(
+  LLZK_CAPI_C_Test
+  PRIVATE
+  LLZK::LLZKCAPI
+  MLIRCAPIIR
+  MLIRCAPIRegisterEverything)
+add_test(NAME LLZK_CAPI_C_Test COMMAND LLZK_CAPI_C_Test)
+list(APPEND LLZK_UNITTESTS LLZK_CAPI_C_Test)
+
+# CAPI unit tests defined via C++ sources
 file(GLOB_RECURSE LLZK_CAPI_TEST_SOURCES "*.cpp")
 add_executable(LLZK_CAPI_Tests ${LLZK_CAPI_TEST_SOURCES})
 

unittests/CAPI/c_compatibility_test.c

@@ -0,0 +1,91 @@
+/*===-- c_compatibility_test.c - Test C API from pure C -----------*- C -*-===//
+ *
+ * Part of the LLZK Project, under the Apache License v2.0.
+ * See LICENSE.txt for license information.
+// Copyright 2026 Project LLZK
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ *===----------------------------------------------------------------------===//
+ *
+ * This file tests that the LLZK C API can be consumed from pure C code.
+ * It verifies that all headers are properly wrapped in extern "C" blocks.
+ *
+ *===----------------------------------------------------------------------===*/
+
+#include "llzk-c/Builder.h"
+#include "llzk-c/Constants.h"
+#include "llzk-c/InitDialects.h"
+#include "llzk-c/Support.h"
+#include "llzk-c/Transforms.h"
+#include "llzk-c/Typing.h"
+#include "llzk-c/Validators.h"
+
+/* Include all dialect headers */
+#include "llzk-c/Dialect/Array.h"
+#include "llzk-c/Dialect/Bool.h"
+#include "llzk-c/Dialect/Cast.h"
+#include "llzk-c/Dialect/Constrain.h"
+#include "llzk-c/Dialect/Felt.h"
+#include "llzk-c/Dialect/Function.h"
+#include "llzk-c/Dialect/Global.h"
+#include "llzk-c/Dialect/Include.h"
+#include "llzk-c/Dialect/LLZK.h"
+#include "llzk-c/Dialect/POD.h"
+#include "llzk-c/Dialect/Poly.h"
+#include "llzk-c/Dialect/String.h"
+#include "llzk-c/Dialect/Struct.h"
+
+#include <mlir-c/BuiltinAttributes.h>
+#include <mlir-c/BuiltinTypes.h>
+#include <mlir-c/IR.h>
+#include <mlir-c/RegisterEverything.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+ * Test basic C API functionality
+ */
+int test_basic_api(void) {
+  /* Create context */
+  MlirContext context = mlirContextCreate();
+  if (mlirContextIsNull(context)) {
+    fprintf(stderr, "Failed to create MLIR context\n");
+    return 1;
+  }
+
+  /* Register dialects */
+  MlirDialectRegistry registry = mlirDialectRegistryCreate();
+  mlirRegisterAllDialects(registry);
+  llzkRegisterAllDialects(registry);
+  mlirContextAppendDialectRegistry(context, registry);
+  mlirContextLoadAllAvailableDialects(context);
+  mlirDialectRegistryDestroy(registry);
+
+  /* Test creating a simple attribute */
+  MlirAttribute publicAttr = llzkPublicAttrGet(context);
+  if (mlirAttributeIsNull(publicAttr)) {
+    fprintf(stderr, "Failed to create PublicAttr\n");
+    mlirContextDestroy(context);
+    return 1;
+  }
+
+  /* Test "isa" check */
+  int isPublic = llzkAttributeIsAPublicAttr(publicAttr);
+  if (!isPublic) {
+    fprintf(stderr, "PublicAttr type check failed\n");
+    mlirContextDestroy(context);
+    return 1;
+  }
+
+  /* Clean up */
+  mlirContextDestroy(context);
+
+  printf("All C API tests passed!\n");
+  return 0;
+}
+
+int main(void) {
+  int result = test_basic_api();
+  return result;
+}