[KT-41655] Add test for incomplete types

backend.native/tests/build.gradle

@@ -3583,6 +3583,12 @@ createInterop("auxiliaryCppSources") {
     it.extraOpts "-Xsource-compiler-option", "-std=c++17"
 }
 
+createInterop("incomplete_types") {
+    it.defFile 'interop/incomplete_types/library.def'
+    it.headers "$projectDir/interop/incomplete_types/library.h"
+    it.extraOpts "-Xcompile-source", "$projectDir/interop/incomplete_types/library.cpp"
+}
+
 createInterop("embedStaticLibraries") {
     it.defFile 'interop/embedStaticLibraries/embedStaticLibraries.def'
     it.headers "$projectDir/interop/embedStaticLibraries/embedStaticLibraries.h"
@@ -3838,6 +3844,14 @@ interopTest("interop_auxiliarySources") {
     interop = 'auxiliaryCppSources'
 }
 
+interopTest("interop_incompleteTypes") {
+    disabled = (project.testTarget == 'wasm32') // No interop for wasm yet.
+    source = "interop/incomplete_types/main.kt"
+    interop = 'incomplete_types'
+}
+
+
+
 interopTest("interop_embedStaticLibraries") {
     disabled = (project.testTarget == 'wasm32') // No interop for wasm yet.
     source = "interop/embedStaticLibraries/main.kt"

backend.native/tests/interop/incomplete_types/library.cpp

@@ -0,0 +1,50 @@
+#include "library.h"
+
+extern "C" {
+
+struct S {
+    const char* name;
+};
+
+struct S s = {
+    .name = "initial"
+};
+
+void setContent(struct S* s, const char* name) {
+    s->name = name;
+}
+
+const char* getContent(struct S* s) {
+    return s->name;
+}
+
+union U {
+    float f;
+    double d;
+};
+
+void setDouble(union U* u, double value) {
+    u->d = value;
+}
+
+double getDouble(union U* u) {
+    return u->d;
+}
+
+union U u = {
+    .d = 0.0
+};
+
+char array[5] = { 0, 0, 0, 0, 0 };
+
+void setArrayValue(char* array, char value) {
+    for (int i = 0; i < 5; ++i) {
+        array[i] = value;
+    }
+}
+
+int arrayLength() {
+    return sizeof(array) / sizeof(char);
+}
+
+}

backend.native/tests/interop/incomplete_types/library.h

@@ -0,0 +1,27 @@
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+// Forward declaration.
+struct S;
+extern struct S s;
+
+const char* getContent(struct S* s);
+void setContent(struct S* s, const char* name);
+
+union U;
+extern union U u;
+
+double getDouble(union U* u);
+void setDouble(union U* u, double value);
+
+// Global array of unknown size.
+extern char array[];
+
+
+int arrayLength();
+void setArrayValue(char* array, char value);
+
+#ifdef __cplusplus
+}
+#endif

backend.native/tests/interop/incomplete_types/main.kt

@@ -0,0 +1,25 @@
+import library.*
+import kotlinx.cinterop.*
+import kotlin.test.*
+
+fun main() {
+    assertNotNull(s.ptr)
+    assertNotNull(u.ptr)
+    assertNotNull(array)
+
+    assertEquals("initial", getContent(s.ptr)?.toKString())
+    setContent(s.ptr, "yo")
+    assertEquals("yo", getContent(s.ptr)?.toKString())
+
+    assertEquals(0.0, getDouble(u.ptr))
+    setDouble(u.ptr, Double.MIN_VALUE)
+    assertEquals(Double.MIN_VALUE, getDouble(u.ptr))
+
+    for (i in 0 until arrayLength()) {
+        assertEquals(0x0, array[i])
+    }
+    setArrayValue(array, 0x1)
+    for (i in 0 until arrayLength()) {
+        assertEquals(0x1, array[i])
+    }
+}