WAMR vmcore is the runtime library set that loads and runs Wasm modules. This guide walks you through building the WAMR vmcore.
References:
Include the script runtime_lib.cmake from build-scripts into your CMakeLists.txt to pull vmcore into your build.
# add this into your CMakeLists.txt
include (${WAMR_ROOT_DIR}/build-scripts/runtime_lib.cmake)
add_library(vmlib ${WAMR_RUNTIME_LIB_SOURCE})
The runtime_lib.cmake script exposes variables that control WAMR runtime features. Set them in CMakeLists.txt or pass them on the cmake command line.
# Set flags in CMakeLists.txt
set(WAMR_BUILD_AOT 1)
set(WAMR_BUILD_JIT 0)
set(WAMR_BUILD_LIBC_BUILTIN 1)
set(WAMR_BUILD_LIBC_WASI 1)
# Include the runtime lib script
include (${WAMR_ROOT_DIR}/build-scripts/runtime_lib.cmake)
add_library(vmlib ${WAMR_RUNTIME_LIB_SOURCE})
Privileged Features are powerful options that can boost performance or add capabilities but lower security by compromising isolation. Use them with care and test thoroughly.
Above compilation flags map to macros in config.h. For example, WAMR_BUILD_AOT maps to WAMR_BUILD_AOT in config.h. The build system sets these macros automatically based on your CMake settings. If your build doesn't set those flags, default values in config.h apply.
WAMR_BUILD_PLATFORM: set the target platform. Match the platform folder name under core/shared/platform.
WAMR_BUILD_TARGET: set the target CPU architecture. Supported targets: X86_64, X86_32, AARCH64, ARM, THUMB, XTENSA, ARC, RISCV32, RISCV64, and MIPS.
<arch>[<sub-arch>][_VFP]. <sub-arch> is the ARM sub-architecture. _VFP means arguments and returns use VFP coprocessor registers s0-s15 (d0-d7). Both are optional, for example ARMV7, ARMV7_VFP, THUMBV7, or THUMBV7_VFP.<arch>[<sub-arch>]. VFP is on by default. <sub-arch> is optional, for example AARCH64, AARCH64V8, or AARCH64V8.1.<arch>[_abi]. _abi is optional. Supported: RISCV64, RISCV64_LP64D, and RISCV64_LP64. RISCV64 and RISCV64_LP64D both use LP64D (LP64 with hardware floating-point for FLEN=64). RISCV64_LP64 uses LP64 (integer calling convention only; no hardware floating-point calling convention).For RISCV32, use <arch>[_abi]. _abi is optional. Supported: RISCV32, RISCV32_ILP32D, RISCV32_ILP32F, and RISCV32_ILP32. RISCV32 and RISCV32_ILP32D both use ILP32D (ILP32 with hardware floating-point for FLEN=64). RISCV32_ILP32F uses ILP32F (ILP32 with hardware floating-point for FLEN=32). RISCV32_ILP32 uses ILP32 (integer calling convention only).
cmake -DWAMR_BUILD_PLATFORM=linux -DWAMR_BUILD_TARGET=ARM
WAMR_BUILD_INTERP=1/0: turn the WASM interpreter on or off.
WAMR_BUILD_FAST_INTERP=1/0: pick fast (default) or classic interpreter.
[!NOTE] The fast interpreter runs ~2X faster than classic interpreter, but consumes about 2X memory to hold the pre-compiled code.
Comparing with fast JIT, LLVM JIT covers more architectures and produces better optimized code, but takes longer on cold start.
The fast JIT is a lightweight JIT that emits code quickly and tunes hot functions.
[!WARNING] It currently covers only a few architectures (x86_64).
Use fast jit as the first tier and LLVM JIT as the second tier.
[!WARNING] It currently covers only a few architectures (x86_64).
WAMR_BUILD_LIBC_BUILTIN=1/0: build the built-in libc subset for WASM apps. Defaults to on.
WAMR_BUILD_LIBC_WASI=1/0: build the WASI libc subset for WASM apps. Defaults to on.
WAMR_BUILD_LIBC_UVWASI=1/0 (Experiment): build the WASI libc subset for WASM apps using uvwasi. Defaults to off.
WAMR_BUILD_LIBC_EMCC=1/0: build the emcc-compatible libc subset for WASM apps. Defaults to off.
[!WARNING] WAMR is not a secure sandbox on every platform. On platforms where WAMR_BUILD_LIBC_WASI is unsupported (for example Windows), you can try the uvwasi-based WASI via WAMR_BUILD_LIBC_UVWASI, but it is unsafe.
[!NOTE] See Multiple Modules as Dependencies for details.
[!WARNING] The multi-module feature is not supported in fast-jit or llvm-jit modes.
[!NOTE] The mini loader skips integrity checks on the WASM binary. Make sure the file is valid yourself.
[!WARNING] This is a privileged feature that compromises security. Use it only when you trust the WASM binary source.
[!WARNING] Supported only in classic interpreter mode and AOT mode.
[!NOTE] When you enable lib pthread, required features such as
shared memoryandthread managerare enabled automatically. See WAMR pthread library for details.
[!NOTE] This depends on
lib-pthreadand turns it on automatically.
[!NOTE] Enabling lib wasi-threads also enables its dependencies
shared memoryandthread manager. See wasi-threads and Introduction to WAMR WASI threads for details.
[!NOTE] Using WAMR_BUILD_WASI_NN without WAMR_BUILD_WASI_EPHEMERAL_NN is deprecated and may be removed later. Please enable WAMR_BUILD_WASI_EPHEMERAL_NN too. See WASI-NN for details.
WAMR_BUILD_WASI_NN_ENABLE_EXTERNAL_DELEGATE=1/0, default to off.
WAMR_BUILD_WASI_NN_EXTERNAL_DELEGATE_PATH=Path to the external delegate shared library (for example libedgetpu.so.1.0 for Coral USB).
wasi_ephemeral_nn module support[!NOTE] By default only linux/darwin/android/windows/vxworks 64-bit platforms enable this hardware trap boundary check. On 32-bit platforms it is off even if the flag is 0. The wamrc tool omits boundary check instructions in AOT code for all 64-bit targets except SGX to improve speed. The boundary check covers linear memory access and native stack access unless
WAMR_DISABLE_STACK_HW_BOUND_CHECKis set.
WAMR_DISABLE_HW_BOUND_CHECK. Otherwise, software boundary checks are used.[!NOTE] If hardware trap boundary checks are off (or
WAMR_DISABLE_HW_BOUND_CHECKis 1), native stack boundary checks are also off regardless ofWAMR_DISABLE_STACK_HW_BOUND_CHECK. If hardware trap boundary checks are on, this setting decides whether the native stack check is on.
[!NOTE] This feature lets blocking threads terminate asynchronously. If you disable it, blocking threads may never finish when asked to exit.
SIMDE (SIMD Everywhere) implements SIMD operations in fast interpreter mode.
[!WARNING] Supported in AOT, JIT, and fast-interpreter modes with the SIMDe library.
[!NOTE] When enabled, SIMDe (SIMD Everywhere) implements SIMD operations in fast interpreter mode.
[!NOTE] Current implementation supports only Legacy Wasm exception handling proposal, not the latest version.
[!WARNING] Exception handling currently works only in classic interpreter mode.
[!WARNING] Garbage collection is not supported in fast-jit mode and multi-tier-jit mode.
[!WARNING] Multi memory is supported only in classic interpreter mode.
[!NOTE] When enabled, AOT or JIT stack frames (similar to classic interpreter frames but storing only what is needed) are built during calls. Add
--enable-dump-call-stackto wamrc when compiling AOT modules.
[!NOTE] When enabled, the runtime dumps the call stack on exceptions.
- In interpreter mode, names come first from the custom name section. If that section is absent or disabled, names come from import/export sections.
- In AOT/JIT mode, names come from the import/export section. Export as many functions as possible (for
wasi-sdkyou can use-Wl,--export-all) when compiling the wasm module, and add--enable-dump-call-stack --emit-custom-sections=nameto wamrc when compiling the AOT module.
[!NOTE] When enabled, call
void wasm_runtime_dump_mem_consumption(wasm_exec_env_t exec_env)to dump memory usage. Currently only module, module_instance, and exec_env memory are measured; other components such aswasi-ctx,multi-module, andthread-managerare not included. See Memory usage estimation for a module.
[!NOTE] When enabled, call
void wasm_runtime_dump_perf_profiling(wasm_module_inst_t module_inst)to dump per-function performance. Function name lookup follows the same order as the dump call stack feature. See Tune the performance of running wasm/aot file.
[!NOTE] When enabled, WAMR uses a big global heap for runtime and wasm apps instead of allocating memory from the system directly. This can reduce memory fragmentation and improve performance when many small allocations happen. The global heap is allocated at startup. WAMR_BUILD_GLOBAL_HEAP_POOL applies to iwasm apps in
product-mini. For your own host app, setmem_alloc_typetoAlloc_With_Poolif you want to use a global heap. The global heap is described in Memory model and memory usage tunning. WAMR_BUILD_GLOBAL_HEAP_SIZE applies to iwasm apps inproduct-mini. For your host app, setmem_alloc_option.poolwith the size you want for the global heap. The global heap is described in Memory model and memory usage tunning.
[!NOTE] AOT boundary checks with hardware traps may use large stacks because the OS can grow stacks lazily when a guard page is hit. Use this setting to cap total stack use, for example
-DWAMR_APP_THREAD_STACK_SIZE_MAX=131072(128 KB).
[!NOTE] If you provide
vprintf_callback,os_printf()andos_vprintf()on Linux, Darwin, Windows, VxWorks, Android, and esp-idf, plus WASI libc output, call your callback instead of libcvprintf(). Example outside the runtime lib:> int my_vprintf(const char *format, va_list ap) > { > /* output to pre-opened file stream */ > FILE *my_file = ...; > return vfprintf(my_file, format, ap); > /* or output to pre-opened file descriptor */ > int my_fd = ...; > return vdprintf(my_fd, format, ap); > /* or output to string buffer and print the string */ > char buf[128]; > vsnprintf(buf, sizeof(buf), format, ap); > return my_printf("%s", buf); > } > ``` > > Then run `cmake -DWAMR_BH_VPRINTF=my_vprintf ..`, or add the compiler macro `BH_VPRINTF=my_vprintf` (for example `add_definitions(-DBH_VPRINTF=my_vprintf)` in CMakeLists.txt). See [basic sample](../samples/basic/src/main.c) for an example. ### **WAMR_BH_LOG**=<log_callback>, default to off. > [!NOTE] > If you provide `log_callback`, WAMR logs go there. Example: > > ```C > void my_log(uint32 log_level, const char *file, int line, const char *fmt, ...) > { > /* Usage of custom logger */ > } > ``` > > See [basic sample](../samples/basic/src/main.c) for an example. ### **reference types feature** - **WAMR_BUILD_REF_TYPES**=1/0, default to on. ### **Exclude WAMR application entry functions** - **WAMR_DISABLE_APP_ENTRY**=1/0, default to off. > [!NOTE] > The WAMR application entry (`core/iwasm/common/wasm_application.c`) wraps common steps to instantiate and run wasm functions and print results. These use platform APIs. this flag to skip the file if your platform lacks those APIs. _Do not enable this flag when building `product-mini`._ ### **source debugging features** - **WAMR_BUILD_DEBUG_INTERP**=1/0, default to off. - **WAMR_BUILD_DEBUG_AOT**=1/0, default to off. - **WAMR_BUILD_DYNAMIC_AOT_DEBUG**=1/0, default to off. > [!NOTE] > Source debugging needs extra setup. See [source_debugging.md](./source_debugging.md) and [WAMR source debugging basic](https://bytecodealliance.github.io/wamr.dev/blog/wamr-source-debugging-basic). ### **load wasm custom sections** - **WAMR_BUILD_LOAD_CUSTOM_SECTION**=1/0, default to off. > [!NOTE] > By default, custom sections are ignored. `WAMR_BUILD_LOAD_CUSTOM_SECTION` so the embedder can read them via `wasm_runtime_get_custom_section`. If `WAMR_BUILD_CUSTOM_NAME_SECTION` is on, the custom name section is consumed by the runtime and unavailable to the embedder. For AoT files, pass `--emit-custom-sections` to wamrc to keep the sections; otherwise they are dropped. ### **Stack guard size** - **WAMR_BUILD_STACK_GUARD_SIZE**=n, default to N/A when not set. > [!NOTE] > By default, stack guard size is 1K (1024) or 24K when uvwasi is enabled. ### **Disable writing the linear memory base address to x86 GS segment register** - **WAMR_DISABLE_WRITE_GS_BASE**=1/0, default to on if the platform supports it. > [!NOTE] > By default only [linux x86-64](https://github.com/bytecodealliance/wasm-micro-runtime/blob/5fb5119239220b0803e7045ca49b0a29fe65e70e/core/shared/platform/linux/platform_internal.h#L67) enables this. On 32-bit platforms it stays off even if set to 0. On linux x86-64, writing the linear memory base to the GS segment can speed up linear memory access for LLVM AOT/JIT when `--enable-segue=[<flags>]` is passed to `wamrc` or `iwasm`. > > See [segue optimization for wamrc when generating the aot file](./perf_tune.md#3-enable-segue-optimization-for-wamrc-when-generating-the-aot-file) for details. ### **User defined linear memory allocator** - **WAMR_BUILD_ALLOC_WITH_USAGE**=1/0, default to off. - **WAMR_BUILD_ALLOC_WITH_USER_DATA**=1/0, default to off. > [!NOTE] > By default, the system allocates linear memory. With this on and `Alloc_With_Allocator` selected, you can provide your own allocator. ### **running PGO(Profile-Guided Optimization) instrumented AOT file** - **WAMR_BUILD_STATIC_PGO**=1/0, default to off. > [!NOTE] > See [Use the AOT static PGO method](./perf_tune.md#5-use-the-aot-static-pgo-method). ### **linux perf support** - **WAMR_BUILD_LINUX_PERF**=1/0: enable linux perf support to generate flamegraphs for wasm app performance. Default is off. > [!NOTE] > See [Use linux-perf](./perf_tune.md#7-use-linux-perf). ### **module instance context APIs** - **WAMR_BUILD_MODULE_INST_CONTEXT**=1/0: enable module instance context APIs so the embedder can set one or more contexts for a wasm module instance. Default is on.C
wasm_runtime_create_context_key wasm_runtime_destroy_context_key wasm_runtime_set_context wasm_runtime_set_context_spread wasm_runtime_get_context> [!NOTE] > See [wasm_export.h](../core/iwasm/include/wasm_export.h) for details. ### **quick AOT/JTI entries** - **WAMR_BUILD_QUICK_AOT_ENTRY**=1/0: register quick call entries to speed up AOT/JIT function calls. Default is on. > [!NOTE] > See [Refine callings to AOT/JIT functions from host native](./perf_tune.md#83-refine-callings-to-aotjit-functions-from-host-native). ### **AOT intrinsics** - **WAMR_BUILD_AOT_INTRINSICS**=1/0: turn on AOT intrinsic functions. Default is on. AOT code can call these when wamrc uses `--disable-llvm-intrinsics` or `--enable-builtin-intrinsics=<intr1,intr2,...>`. > [!NOTE] > See [Tuning the XIP intrinsic functions](./xip.md#tuning-the-xip-intrinsic-functions). ### **extended constant expression** - **WAMR_BUILD_EXTENDED_CONST_EXPR**=1/0, default to off. > [!NOTE] > See [Extended Constant Expressions](https://github.com/WebAssembly/extended-const/blob/main/proposals/extended-const/Overview.md). ### **bulk-memory-opt** - **WAMR_BUILD_BULK_MEMORY_OPT**=1/0, default to off. > [!NOTE] > See [bulk-memory-opt](https://github.com/WebAssembly/tool-conventions/blob/main/Lime.md#bulk-memory-opt). ### **call-indirect-overlong** - **WAMR_BUILD_CALL_INDIRECT_OVERLONG**=1/0, default to off. > [!NOTE] > See [call-indirect-overlong](https://github.com/WebAssembly/tool-conventions/blob/main/Lime.md#call-indirect-overlong). ### **Lime1 target** - **WAMR_BUILD_LIME1**=1/0, default to off. > [!NOTE] > See [Lime1](https://github.com/WebAssembly/tool-conventions/blob/main/Lime.md#lime1). ### **Configurable memory access boundary check** - **WAMR_CONFIGURABLE_BOUNDS_CHECKS**=1/0, default to off. > [!WARNING] > When enabled, you can run `iwasm --disable-bounds-checks` to turn off memory access boundary checks in interpreter mode. This is a [privileged feature](#privileged-features); use it carefully. ### **Shared heap among wasm apps and host native** - **WAMR_BUILD_SHARED_HEAP**=1/0, default to off. > [!NOTE] > When enabled, you can create and attach shared heaps, and the following APIs become available: > > ```C > wasm_runtime_create_shared_heap > wasm_runtime_attach_shared_heap > wasm_runtime_detach_shared_heap > wasm_runtime_shared_heap_malloc > wasm_runtime_shared_heap_free > ``` > > A wasm app can call these to use the shared heap attached to its module instance: > > ```C > void *shared_heap_malloc(); > void shared_heap_free(void *ptr); > ``` > [!WARNING] > The shared-heap feature is not supported in fast-jit mode. ### **Shrunk the memory usage** - **WAMR_BUILD_SHRUNK_MEMORY**=1/0, default to on. > [!NOTE] > When enabled, this reduces memory by shrinking linear memory, especially when `memory.grow` is unused and memory needs are predictable. ### **Instruction metering** - **WAMR_BUILD_INSTRUCTION_METERING**=1/0, default to off. > [!NOTE] > This limits the number of instructions a wasm module instance can run. Call `wasm_runtime_set_instruction_count_limit(...)` before `wasm_runtime_call_*(...)` to enforce the cap. > [!WARNING] > This is only supported in classic interpreter mode. ### **Invoke general FFI** - **WAMR_BUILD_INVOKE_NATIVE_GENERAL**=1/0, default to off. By default, WAMR uses architecture-specific calling conventions to call native functions from WASM modules. When this feature is enabled, WAMR uses a general calling convention that works on all architectures but is slower. The details are in [iwasm_common.cmake](../core/iwasm/common/iwasm_common.cmake) ### **Host defined log** - **WAMR_BH_LOG**=<log_callback>, default to off. ### **AOT Validator** - **WAMR_BUILD_AOT_VALIDATOR**=1/0, default to off. > [!NOTE] > By default, WAMR believes AOT files are valid and unforged. ### **Copy Call Stack** - **WAMR_BUILD_COPY_CALL_STACK**=1/0, default to off. > [!NOTE] > Unlike [dump call stack](dump-call-stack-feature), which prints the call stack on exceptions, this feature lets the embedder copy the call stack programmatically via `wasm_runtime_dump_call_stack_to_buf()`. ### **Librats** - **WAMR_BUILD_LIB_RATS**=1/0, default to off. > [librats](https://github.com/inclavare-containers/librats) is a C library designed to facilitate remote attestation for secure computing environments. It provides a framework for attesting the integrity of computing environments remotely, enabling trust establishment between different Trusted Execution Environments (TEEs). > [!WARNING] > This is for Intel SGX platforms only. ### **Sanitizer** - **WAMR_BUILD_SANITIZER**=[ubsan|asan|tsan|posan], default is empty Use one or more of the following sanitizers when building WAMR with sanitizer support: AddressSanitizer, UndefinedBehaviorSanitizer, ThreadSanitizer, or Pointer-Overflow Sanitizer. ### **Intel Protected File System** - **WAMR_BUILD_SGX_IPFS**=1/0, default to off. > [!WARNING] > This is for Intel SGX platforms only. ### **Support spec test** - **WAMR_BUILD_SPEC_TEST**=1/0, default to off. ### **WASM Cache** - **WAMR_BUILD_WASM_CACHE**=1/0, default to off. ### **Test Garbage Collection** - **WAMR_TEST_GC**=1/0, default to off. It is used to test garbage collection related APIs and features. Refer to [iwasm_gc.cmake](../core/iwasm/common/gc/iwasm_gc.cmake) for details. It is used to cache loaded wasm modules in memory to speed up module instantiation only in wasm-c-api. ## **Combination of configurations** You can mix settings. For example, to disable the interpreter, enable AOT and WASI, run:Bash cmake .. -DWAMR_BUILD_INTERP=0 -DWAMR_BUILD_AOT=1 -DWAMR_BUILD_LIBC_WASI=1 -DWAMR_BUILD_PLATFORM=linux
To enable the interpreter, disable AOT and WASI, and target X86_32, run:Bash cmake .. -DWAMR_BUILD_INTERP=1 -DWAMR_BUILD_AOT=0 -DWAMR_BUILD_LIBC_WASI=0 -DWAMR_BUILD_TARGET=X86_32
When enabling SIMD for fast interpreter mode, turn on both SIMD and the SIMDe library:Bash
cmake .. -DWAMR_BUILD_INTERP=1 -DWAMR_BUILD_FAST_INTERP=1 -DWAMR_BUILD_SIMD=1 -DWAMR_BUILD_LIB_SIMDE=1
For Valgrind, start with these and add more as needed:
Bash #... -DCMAKE_BUILD_TYPE=Debug \ -DWAMR_DISABLE_HW_BOUND_CHECK=0 \ -DWAMR_DISABLE_WRITE_GS_BASE=0 #...
To enable the minimal Lime1 feature set, turn off features that are on by default such as bulk memory and reference types:
Bash cmake .. -DWAMR_BUILD_LIME1=1 -DWAMR_BUILD_BULK_MEMORY=0 -DWAMR_BUILD_REF_TYPES=0 -DDWAMR_BUILD_SIMD=0 ```