before the change, only support wasm app exit like:
```c
void *thread_routine(void *arg)
{
printf("Enter thread\n");
return NULL;
}
```
if call pthread_exit, it will crash:
```c
void *thread_routine(void *arg)
{
printf("Enter thread\n");
pthread_exit(NULL);
return NULL;
}
```
This commit lets both upstairs work correctly, test pass on stm32f103 mcu.
And refactor the original perf support
- use WAMR_BUILD_LINUX_PERF as the cmake compilation control
- use WASM_ENABLE_LINUX_PERF as the compiler macro
- use `wamrc --enable-linux-perf` to generate aot file which contains fp operations
- use `iwasm --enable-linux-perf` to create perf map for `perf record`
The host embedder may also want to terminate the wasm instance
for single-threading mode, and it should work by setting exception
to the wasm instance.
Loggers (e.g. glog) usually come with instrumentation to add timestamp
and other information when reporting. That results in the timestamp
being reported twice, making the output confusing.
According to the specification:
```
When instantiating a module which is expected to run
with `wasi-threads`, the WASI host must first allocate shared memories to
satisfy the module's imports.
```
Currently, if a test from the spec is executed while having the `multi-module`
feature enabled, WAMR fails with `WASM module load failed: unknown import`.
That happens because spec tests use memory like this:
`(memory (export "memory") (import "foo" "bar") 1 1 shared)`
and WAMR tries to find a registered module named `foo`.
At the moment, there is no specific module name that can be used to identify
that the memory is imported because using WASI threads:
https://github.com/WebAssembly/wasi-threads/issues/33,
so this PR only avoids treating the submodule dependency not being found
as a failure.
It's possible to set both `atim` and `atim_now` in the `fstflags`
parameter. Same goes for `mtin` and `mtim_now`. However, it's
ambiguous which time should be set in these two cases. This commit
checks this and returns `EINVAL`.
A wasm module can be either a command or a reactor, so it can export
either `_start` or `_initialize`. Currently, if a command module is run,
`iwasm` still looks for `_initialize`, resulting in the warning:
`can not find an export 0 named _initialize in the module`.
Change to look for `_initialize` only if `_start` not found to resolve the issue.
This fixes bug #2880. Zephyr 3.2 made changes to how headers are reference (see [release notes](https://docs.zephyrproject.org/latest/releases/release-notes-3.2.html)). Work item [49578](https://github.com/zephyrproject-rtos/zephyr/issues/49578) deprecated the old headers names.
The current WAMR codebase references these old headers, thus causing compile errors with
current versions of Zephyr.
This update adds #ifdefs around the header names. With this change, compiling with Zephyr 3.2.0
and above will use the new header files. Prior versions will use the existing code.
This commit adds a check to `fd_advise`. If the fd is a directory,
return `ebadf`. This brings iwasm in line with Wasmtime's behavior.
WASI folks have stated that fd_advise should not work on directories
as this is a Linux-specific behavior:
https://github.com/bytecodealliance/wasmtime/issues/6505#issuecomment-1574122949
- Fix op_br_table arity type check when the dest block is loop block
- Fix op_drop issue when the stack is polymorphic and it is to drop
an ANY type value in the stack
* Empty names are spec-wise valid.
* As we ignore unknown custom sections anyway, it's safe to
accept empty names here.
* Currently, the problem is not exposed on our CI because
the wabt version used there is a bit old.
For shared memory, runtime should get the memories pointer from
module_inst first, then get memory instance from memories array,
and then get the fields of the memory instance.
Support new a wasm_config_t, set allocation and linux_perf_support
options to it, and then pass it to wasm_engine_new_with_config to
new an engine with private configuration.
The JSON evidence is allocated on the module instance heap, but no API
was given to dispose of this memory buffer. The sample mentions using
the function free, which behaves differently depending on the
execution context.
This fix provides a new function called librats_dispose_evidence_json,
enabling freeing the JSON evidence directly from the Wasm app.
Change WASMMemoryInstance's field is_shared_memory's type from bool
to uint8 whose size is fixed, so as to make WASMMemoryInstance's size
and layout fixed and not break AOT ABI.
See discussion in https://github.com/bytecodealliance/wasm-micro-runtime/pull/2682.
The popped reachable block may be if block whose else branch hasn't been
translated, and should push the params for the else block if there are.
And use LLVMDisposeMessage to free memory allocated in is_win_platform.
Currently, `data.drop` instruction is implemented by directly modifying the
underlying module. It breaks use cases where you have multiple instances
sharing a single loaded module. `elem.drop` has the same problem too.
This PR fixes the issue by keeping track of which data/elem segments have
been dropped by using bitmaps for each module instances separately, and
add a sample to demonstrate the issue and make the CI run it.
Also add a missing check of dropped elements to the fast-jit `table.init`.
Fixes: https://github.com/bytecodealliance/wasm-micro-runtime/issues/2735
Fixes: https://github.com/bytecodealliance/wasm-micro-runtime/issues/2772
CryptGenRandom is deprecated by Microsoft and may be removed in future
releases. They recommend to use the next generation API instead. See
https://learn.microsoft.com/en-us/windows/win32/seccng/cng-portal for
more details. Also, refactor the random functions to return error codes
rather than aborting the program if they fail.
Error is reported when executing `wamrc --target=thumb -o <aot_file> <wasm_file>`:
```
LLVM ERROR: failed to perform tail call elimination on a call site marked musttail
Aborted (core dumped)
```
Set `abi` to "gnu" for the bare-metal target when `abi` is NULL,
or the below `bh_assert` and `bh_memcpy` may deference a NULL
pointer. Error is reported when running wamrc compiled with
`cmake .. -DCMAKE_BUILD_TYPE=Debug`:
```
core/iwasm/compilation/aot_llvm.c:2584:13: runtime error:
null pointer passed as argument 1, which is declared to never be null
```
Add an extra argument `os_file_handle file` for `os_mmap` to support
mapping file from a file fd, and remove `os_get_invalid_handle` from
`posix_file.c` and `win_file.c`, instead, add it in the `platform_internal.h`
files to remove the dependency on libc-wasi.
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
Heap corruption check in ems memory allocator is enabled by default
to improve the security, but it may impact the performance a lot, this
PR adds cmake variable and compiler flag to enable/disable it.
Returning uint16 from WASI functions is technically correct. However,
the smallest integer type in WASM is int32 and since we don't guarantee
that the upper 16 bits of the result are zero'ed, it can result in
tricky bugs if the language SDK being used in the WASM app does not cast
back immediately to uint16. To prevent this, we directly return uint32
instead, so that the result is well-defined as a 32-bit number.
Set the vendor-sys of bare-metal targets to "-unknown-none-",
and currently only add "thumbxxx" to the bare-metal target list.
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
The commit fa5e9d72b0 ("Abstract POSIX filesystem functions") introduces
the build warning:
./core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/posix.c: In function ‘fd_object_release’:
./core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/posix.c:545:20: warning: this statement may fall through [-Wimplicit-fallthrough=]
545 | if (os_is_dir_stream_valid(&fo->directory.handle)) {
| ^
./core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/posix.c:549:13: note: here
549 | default:
| ^~~~~~~
Refer to the commit fb4afc7ca4 ("Apply clang-format for core/iwasm compilation and libraries"),
add one line "// Fallthrough." to make compiler happy.
Signed-off-by: Haiyue Wang <haiyue.wang@intel.com>
`platform_common.h` already has a declaration for BH_VPRINTF so we can
get rid of the one in `platform_internal.h`. Also add some explicit
casts to avoid MSVC compiler warnings.
UWP apps do not have a console attached so any output to stdout/stderr
is lost. Therefore, provide a default BH_VPRINTF in that case for debug
builds which redirects output to the debugger.
To allow anything to depend on WASI types, including platform-specific
data structures, move the WASI libc filesystem/clock interface into
`platform_api_extension.h`, which leaves just WASI types in
`platform_wasi.h`. And `platform_wasi.h` has been renamed to
`platform_wasi_types.h` to reflect that it only defines types now and no
function declarations. Finally, these changes allow us to remove the
`windows_fdflags` type which was essentially a duplicate of
`__wasi_fdflags_t`.
Most of the WASI filesystem tests require at least creating/deleting a
file to test filesystem functionality so some additional filesystem APIs
have been implemented on Windows so we can test what has been
implemented so far. For those WASI functions which haven't been
implemented, we skip the tests. These will be implemented in a future PR
after which we can remove the relevant filters.
Additionally, in order to run the WASI socket and thread tests, we need
to install the wasi-sdk in CI and build the test source code prior to
running the tests.
`jit_reg_is_const_val` only checks whether the register is a const register and
the const value is stored in the register.
Should use `jit_reg_is_const` instead in the front end.
Reported in #2710.
- Fix potential invalid push param phis and add incoming phis to a un-existed basic block
- Fix potential invalid shift count int rotl/rotr opcodes
- Resize memory_data_size to UINT32_MAX if it is 4G when hw bound check is enabled
- Fix negative linear memory offset is used for 64-bit target it is const and larger than INT32_MAX
To run it locally:
```bash
export TSAN_OPTIONS=suppressions=<path_to_tsan_suppressions.txt>
./test_wamr.sh <your flags> -T tsan
```
An example for wasi-threads would look like:
```bash
export TSAN_OPTIONS=suppressions=<path_to_tsan_suppressions.txt>
./test_wamr.sh -w -s wasi_certification -t fast-interp -T tsan
```
Split memory instance's field `uint32 ref_count` into `bool is_shared_memory`
and `uint16 ref_count`, and lock the memory only when `is_shared_memory`
flag is true, no need to acquire a lock for non-shared memory when shared
memory feature is enabled.
Avoid repeatedly initializing the shared memory data when creating the child
thread in lib-pthread or lib-wasi-threads.
Add shared memory lock when accessing some fields of the memory instance
if the memory instance is shared.
Init shared memory's memory_data_size/memory_data_end fields according to
the current page count but not max page count.
Add wasm_runtime_set_mem_bound_check_bytes, and refine the error message
when shared memory flag is found but the feature isn't enabled.
Fixes the Cosmopolitan Libc platform attempting to use `/dev/urandom`
on operating systems that do not have it.
Signed-off-by: G4Vi <gavin@dylibso.com>
This patch enables mapping host directories to guest directories by parsing
the `map_dir_list` argument in API `wasm_runtime_init_wasi` for libc-wasi. It
follows the format `<guest-path>::<host-path>`.
It also adds argument `--map-dir=<guest::host>` argument for `iwasm`
common line tool, and allows to add multiple mappings:
```bash
iwasm --map-dir=<guest-path1::host-path1> --map-dir=<guest-path2::host-path2> ...
```
Implement the necessary os_ filesystem functions to enable successful
WASI initialization on Windows. Some small changes were also required to
the sockets implementation to use the new windows_handle type. The
remaining functions will be implemented in a future PR.
When labels-as-values is enabled in a target which doesn't support
unaligned address access, 16-bit offset is used to store the relative
offset between two opcode labels. But it is a little small and the loader
may report "pre-compiled label offset out of range" error.
Emitting 32-bit data instead to resolve the issue: emit label address in
32-bit target and emit 32-bit relative offset in 64-bit target.
See also:
https://github.com/bytecodealliance/wasm-micro-runtime/issues/2635
To allow non-POSIX platforms such as Windows to support WASI libc
filesystem functionality, create a set of wrapper functions which provide a
platform-agnostic interface to interact with the host filesystem. For now,
the Windows implementation is stubbed but this will be implemented
properly in a future PR. There are no functional changes in this change,
just a reorganization of code to move any direct POSIX references out of
posix.c in the libc implementation into posix_file.c under the shared
POSIX sources.
See https://github.com/bytecodealliance/wasm-micro-runtime/issues/2495 for a
more detailed overview of the plan to port the WASI libc filesystem to Windows.
When doing more investigations related to this PR:
https://github.com/bytecodealliance/wasm-micro-runtime/pull/2619
We found that in some scenarios the constant might not be directly
available to the LLVM IR builder, e.g.:
```
(func $const_ret (result i32)
i32.const -5
)
(func $foo
(i32.shr_u (i32.const -1) (call $const_ret))
(i32.const 31)
)
```
In that case, the right parameter to `i32.shr_u` is not constant, therefore
the `SHIFT_COUNT_MASK` isn't applied. However, when the optimization
is enabled (`--opt-level` is 2 or 3), the optimization passes resolve the
call into constant, and that constant is poisoned, causing the compiler to
resolve the whole function to an exception.
According to the description of `buildPerModuleDefaultPipeline()` and
`buildLTOPreLinkDefaultPipeline()`, it is not allowed to call them with `O0` level.
Use `buildO0DefaultPipeline` instead when the opt-level is 0.
The LLVM zext IR may be inserted after the terminator of a basic block
when popping the arguments of a wasm block. Change to insert the
zext IR before the terminator of the basic block to resolve the issue.
Reported in #2620.
This PR adds the Cosmopolitan Libc platform enabling compatibility with multiple
x86_64 operating systems with the same binary. The platform is similar to the
Linux platform, but for now only x86_64 with interpreter modes are supported.
The only major change to the core is `posix.c/convert_errno()` was rewritten to use
a switch statement. With Cosmopolitan errno values depend on the currently
running operating system, and so they are non-constant and cannot be used in array
designators. However, the `cosmocc` compiler allows non-constant case labels in
switch statements, enabling the new version.
And updated wamr-test-suites script to add `-j <platform>` option. The spec tests
can be ran via `CC=cosmocc ./test_wamr.sh -j cosmopolitan -t classic-interp`
or `CC=cosmocc ./test_wamr.sh -j cosmopolitan -t fast-interp`.
To make it clearer to users when synchronization behaviour is not
supported, return ENOTSUP when O_RSYNC, O_DSYNC or O_SYNC are
respectively not defined. Linux also doesn't support O_RSYNC despite the
O_RSYNC flag being defined.
Fixed a bug in the processing of the br_table_cache opcode that caused out-of-range
references when the label index was greater than the length of the label.
Avoid the stack traces getting mixed up together when multi-threading is enabled
by using exception_lock/unlock in dumping the call stacks.
And remove duplicated call stack dump in wasm_application.c.
Also update coding guideline CI to fix the clang-format-12 not found issue.
According to the specification,
- fNxM_pmin/max returns v1 or v2 based on flt(v1,v2) result
- fNxM_min/max returns +/-NaN, +/-Inf, v1 or v2 based on more than
flt(v1,v2) result
Fixes issue #2561.
Only when the value kind is LLVMConstantIntValueKind and the value
is not undef and not poison can we extract the value of a constant int.
Fixes#2557 and #2559.
Support muti-module for AOT mode, currently only implement the
multi-module's function import feature for AOT, the memory/table/
global import are not implemented yet.
And update wamr-test-suites scripts, multi-module sample and some
CIs accordingly.
The CI might use clang-17 to build iwasm for Android platform and it may
report compilation error:
https://github.com/bytecodealliance/wasm-micro-runtime/actions/runs/6308980430/job/17128073777
/home/runner/work/wasm-micro-runtime/wasm-micro-runtime/core/iwasm/libraries/libc-wasi/sandboxed-system-primitives/src/blocking_op.c:45:19: error: call to undeclared function 'preadv'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
ssize_t ret = preadv(fd, iov, iovcnt, offset);
^
Explicitly declare preadv and pwritev in android platform header file to resolve it.
`wasm_loader_push_pop_frame_offset` may pop n operands by using
`loader_ctx->stack_cell_num` to check whether the operand can be
popped or not. While `loader_ctx->stack_cell_num` is updated in the
later `wasm_loader_push_pop_frame_ref`, the check may fail if the stack
is in polymorphic state and lead to `ctx->frame_offset` underflow.
Fix issue #2577 and #2586.
There doesn't appear to be a clear reason not to support this behavior.
It seems it was disallowed previously as a precaution. See
67e2e57b02
for more context.
Adapt API usage to new interfaces where applicable, including LLVM function
usage, obsoleted llvm::Optional type and removal of unavailable headers.
Know issues:
- AOT static PGO isn't enabled
- LLVM JIT may run failed due to llvm_orc_registerEHFrameSectionWrapper
isn't linked into iwasm
Return a WASI error code (rather than a host POSIX one). In addition,
there is no need to return an error in the case that the provided buffer
is too large.
Unaligned store v128 value to the AOT function argument of the pointer for
the extra return value may cause segmentation fault.
Fix the issue reported in #2556.
The WASI docs allow for fewer rights to be applied to an fd than requested but
not more. This behavior is also asserted in the rust WASI tests, so it's necessary
for those to pass as well.
Send a signal whose handler is no-op to a blocking thread to wake up
the blocking syscall with either EINTR equivalent or partial success.
Unlike the approach taken in the `dev/interrupt_block_insn` branch (that is,
signal + longjmp similarly to `OS_ENABLE_HW_BOUND_CHECK`), this PR
does not use longjmp because:
* longjmp from signal handler doesn't work on nuttx
refer to https://github.com/apache/nuttx/issues/10326
* the singal+longjmp approach may be too difficult for average programmers
who might implement host functions to deal with
See also https://github.com/bytecodealliance/wasm-micro-runtime/issues/1910
Remove thread local attribute of prev_sig_act_SIGSEGV/SIGBUS to allow using
custom signal handler from non-main thread since in a thread spawned by
embedder, embedder may be unable to call wasm_runtime_init_thread_env to
initialize them.
And fix the handling of prev_sig_act when its sa_handler is SIG_DFL, SIG_IGN,
or a user customized handler.
Add API wasm_runtime_terminate to terminate a module instance
by setting "terminated by user" exception to the module instance.
And update the product-mini of posix platforms.
Note: this doesn't work for some situations like blocking system calls.
Preserve errno because this function is often used like
the following. The caller wants to report the error from the main
operation (`lseek` in this example), not from fd_object_release.
```
off_t ret = lseek(fd_number(fo), offset, nwhence);
fd_object_release(fo);
if (ret < 0)
return convert_errno(errno);
```
This fixes a few test cases in wasi-threads testsuite like wasi_threads_return_main_block.
And also move the special handling for "wasi proc exit" to a more appropriate place.
Introduce module instance context APIs which can set one or more contexts created
by the embedder for a wasm module instance:
```C
wasm_runtime_create_context_key
wasm_runtime_destroy_context_key
wasm_runtime_set_context
wasm_runtime_set_context_spread
wasm_runtime_get_context
```
And make libc-wasi use it and set wasi context as the first context bound to the wasm
module instance.
Also add samples.
Refer to https://github.com/bytecodealliance/wasm-micro-runtime/issues/2460.
When embedding WAMR, this PR allows to register a callback that is
invoked when memory.grow fails.
In case of memory allocation failures, some languages allow to handle
the error (e.g. by checking the return code of malloc/calloc in C), some
others (e.g. Rust) just panic.
While wasi proc exit is not a real trap, what the runtime does on it is mostly same as
real traps. That is, kill the siblings threads and represent the exit/trap as the result of
the "process" to the user api. There seems no reason to distinguish it from real traps
here.
Note that:
- The target thread either doesn't care the specific exception type or ignore wasi
proc exit by themselves. (clear_wasi_proc_exit_exception)
- clear_wasi_proc_exit_exception only clears local exception.
Add simple infrastructure to add more unit tests in the future. At the moment tests
are only executed on Linux, but can be extended to other platforms if needed.
Use https://github.com/google/googletest/ as a framework.
As a part of stress-testing we want to ensure that mutex implementation is working
correctly and protecting shared resource to be allocated from other threads when
mutex is locked.
This test covers the most common situations that happen when some program uses
mutexes like locks from various threads, locks from the same thread etc.
When AOT out of bound linear memory access or stack overflow occurs, the call stack of
AOT functions cannot be unwound currently, so from the exception handler, runtime
cannot jump back into the place that calls the AOT function.
We temporarily skip the current instruction and let AOT code continue to run and return
to caller as soon as possible. And use the zydis library the decode the current instruction
to get its size.
And remove using RtlAddFunctionTable to register the AOT functions since it doesn't work
currently.
AOT relocation to aot_func_internal#n is generated by wamrc --bounds-checks=1.
Resolve the issue by applying the relocation in the compilation stage by wamrc and
don't generate these relocations in the AOT file.
Fixes#2471.
We need to apply some bug fixes that were merged to wasi-libc because wasi-sdk-20
is about half a year old.
It is a temporary solution and the code will be removed when wasi-sdk 21 is released.
- Fix windows wamrc link error: aot_generate_tempfile_name undefined.
- Clear windows compile warnings.
- And rename folder `samples/bh_atomic` and `samples/mem_allocator` to
`samples/bh-atomic` and `samples/mem-allocator`.
## Context
Some native libraries may want to explicitly delete an externref object without
waiting for the module instance to be deleted.
In addition, it may want to add a cleanup function.
## Proposed Changes
Implement:
* `wasm_externref_objdel` to explicitly delete an externeref'd object.
* `wasm_externref_set_cleanup` to set a cleanup function that is called when
the externref'd object is deleted.
In macro bh_memcpy_s, bh_memcy_wa and bh_memmove_s, no need to do extra check
for length is zero or not because it was already done inside of the functions called.
- Inherit shared memory from the parent instance, instead of
trying to look it up by the underlying module. The old method
works correctly only when every cluster uses different module.
- Use reference count in WASMMemoryInstance/AOTMemoryInstance
to mark whether the memory is shared or not
- Retire WASMSharedMemNode
- For atomic opcode implementations in the interpreters, use
a global lock for now
- Update the internal API users
(wasi-threads, lib-pthread, wasm_runtime_spawn_thread)
Fixes https://github.com/bytecodealliance/wasm-micro-runtime/issues/1962
- Avoid destroying module instance repeatedly in pthread_exit_wrapper and
wasm_thread_cluster_exit.
- Wait enough time in pthread_join_wrapper for target thread to exit and
destroy its resources.
We need to make a test that runs longer than the tests we had before to check
some problems that might happen after running for some time (e.g. memory
corruption or something else).
Tests were failing because the right permissions were not provided to iwasm.
Also, test failures didn't trigger build failure due to typo - also fixed in this change.
In addition to that, this PR fixes a few issues with the test itself:
* the `server_init_complete` was not reset early enough causing the client to occasionally
assume the server started even though it didn't yet
* set `SO_REUSEADDR` on the server socket so the port can be reused shortly after
closing the previous socket
* defined receive-send-receive sequence from server to make sure server is alive at the
time of sending message
The old method may not work for some cases. This PR iterates over all instructions
in the function, looking for memcpy, memmove and memset instructions, putting
them into a set, and finally expands them into a loop one by one.
And move this LLVM Pass after building the pipe line of pass builder to ensure that
the memcpy/memmove/memset instrinsics are generated before applying the pass.
And return ENOSYS. We do that so we can at least compile the code on CI.
We'll be gradually enabling more and more functions.
Also, enabled `proc_raise()` for windows.
* disable translations of errno codes that aren't defined on Windows
* undef `min()` macro if it is defined to not conflict with the `min()` function we define
* implement `shed_yield` wasi call
* disable some of the features in the config for windows by default
There is no standard `realpath` function in the C/C++ standard libraries for Windows,
use `_fullpath` function instead to get absolute path of a directory.
We have observed a significant performance degradation after merging
https://github.com/bytecodealliance/wasm-micro-runtime/pull/1991
Instead of protecting suspend flags with a mutex, we implement the flags
as atomic variable and only use mutex when atomics are not available
on a given platform.
esp32-s3's instruction memory and data memory can be accessed through mutual mirroring way,
so we define a new feature named as WASM_MEM_DUAL_BUS_MIRROR.
Build wasi-libc library on Windows since libuv may be not supported. This PR is a first step
to make it working, but there's still a number of changes to get it fully working.
Allow to use `cmake -DWAMR_CONFIGURABLE_BOUNDS_CHECKS=1` to
build iwasm, and then run `iwasm --disable-bounds-checks` to disable the
memory access boundary checks.
And add two APIs:
`wasm_runtime_set_bounds_checks` and `wasm_runtime_is_bounds_checks_enabled`
Calling `__wasi_sock_addr_resolve` syscall causes native stack overflow.
Given this is a standard function available in WAMR, we should have at least
the default stack size large enough to handle this case.
The socket tests were updated so they also run in separate thread, but
the simple retro program is:
```C
void *th(void *p)
{
struct addrinfo *res;
getaddrinfo("amazon.com", NULL, NULL, &res);
return NULL;
}
int main(int argc, char **argv)
{
pthread_t pt;
pthread_create(&pt, NULL, th, NULL);
pthread_join(pt, NULL);
return 0;
}
```
