How to right way to process C null pointer in Kotl...

# kotlin-native

[rjhdby]

How to right way to process C null pointer in Kotlin function?

[olonho]

Andrey, please use Slack threads for long messages with stacktraces

[rjhdby]

Sorry, I'm not familiar with slack.

Hello! I compile simple library with one function

const val HELLO_EN = "Hello"
fun hello(name: String, lang: String?) = "${lang ?: HELLO_EN} $name!!!\n"

And call it from C-code

example_kt_symbols()->kotlin.root.hello(name, lang)

name - is initialized char *, and lang is unitialized char * aka null pointer

Execution failed on this step

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff4a39f81 in __strlen_sse2_pminub () from /usr/lib64/libc.so.6
(gdb) bt
#0  0x00007ffff4a39f81 in __strlen_sse2_pminub () from /usr/lib64/libc.so.6
#1  0x00007fffe720fadb in CreateStringFromCString () from ./modules/example.so
#2  0x00007fffe71f77fb in _konan_function_7_impl(char const*, char const*) () from ./modules/example.so
#3  0x00007fffe71f7016 in zif_hello (execute_data=<optimized out>, return_value=0x7ffff3a12080) at /root/simpleExtension/example.c:57
#4  0x0000555555802cf6 in ZEND_DO_ICALL_SPEC_RETVAL_USED_HANDLER ()
#5  0x00005555557f2cab in execute_ex ()
#6  0x0000555555846964 in zend_execute ()
#7  0x000055555579c168 in zend_eval_stringl ()
#8  0x000055555579c319 in zend_eval_stringl_ex ()
#9  0x00005555558488e3 in do_cli ()
#10 0x0000555555624bbf in main ()

What I'm doing wrong?

[olonho]

it’s likely K/N bug, in CreateCStringFromString, combined with different behavior of strlen with null arg. Pass “” for now, we will fix it.

[olonho]

smth like

diff --git a/runtime/src/main/cpp/KString.cpp b/runtime/src/main/cpp/KString.cpp
index 890885b2f..00d08ff40 100644
--- a/runtime/src/main/cpp/KString.cpp
+++ b/runtime/src/main/cpp/KString.cpp
@@ -713,7 +713,7 @@ int iswlower_Konan(KChar ch) {
 extern "C" {
 
 OBJ_GETTER(CreateStringFromCString, const char* cstring) {
-  RETURN_RESULT_OF(utf8ToUtf16, cstring, strlen(cstring));
+  RETURN_RESULT_OF(utf8ToUtf16, cstring, cstring ? strlen(cstring) : 0);
 }
 
 OBJ_GETTER(CreateStringFromUtf8, const char* utf8, uint32_t lengthBytes) {

may help

[rjhdby]

Thank!

[olonho]

fixed in master