source_debugging_aot.md

WAMR source debugging (AOT)

Debugging with AOT

Note: AOT debugging is experimental and only a few debugging capabilities are supported.

1. Build lldb (assume you have already built llvm)

cd ${WAMR_ROOT}/core/deps/llvm/build
cmake ../llvm -DLLVM_ENABLE_PROJECTS="clang;lldb" -DLLDB_INCLUDE_TESTS=OFF
make -j $(nproc)

2. Build wamrc with debugging feature

cd ${WAMR_ROOT}/wamr-compiler
mkdir build && cd build
cmake .. -DWAMR_BUILD_DEBUG_AOT=1
make -j $(nproc)

3. Build iwasm with debugging feature

cd ${WAMR_ROOT}/product-mini/platforms/linux
mkdir build && cd build
cmake .. -DWAMR_BUILD_DEBUG_AOT=1
make

4. Compile wasm module to AOT module

wamrc -o test.aot test.wasm

5. Execute iwasm using lldb

   Then you can use lldb commands to debug both wamr runtime and your wasm application in current terminal.

   % lldb iwasm -- test.aot
   (lldb) target create "iwasm"
   Current executable set to 'iwasm' (x86_64).
   (lldb) settings set -- target.run-args  "test.aot"
   (lldb) settings set plugin.jit-loader.gdb.enable on
   (lldb) b main
   Breakpoint 1: where = iwasm`main + 48 at main.c:294:11, address = 0x0000000100001020
   (lldb) run
   Process 27954 launched: '/tmp/bin/iwasm' (x86_64)
   Process 27954 stopped
   * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.1
       frame #0: 0x0000000100001020 iwasm`main(argc=2, argv=0x00007ff7bfeff678) at main.c:294:11
      291  int
      292  main(int argc, char *argv[])
      293  {
   -> 294      int32 ret = -1;
      295      char *wasm_file = NULL;
      296      const char *func_name = NULL;
      297      uint8 *wasm_file_buf = NULL;
   Target 0: (iwasm) stopped.
   (lldb) c
   Process 27954 resuming
   1 location added to breakpoint 1
   error: need to add support for DW_TAG_base_type 'void' encoded with DW_ATE = 0x0, bit_size = 0
   Process 27954 stopped
   * thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 1.2
       frame #0: 0x00000001002980a0 JIT(0x100298004)`main(exenv=0x0000000301808200) at hello.c:6:9
      3    int
      4    main(void)
      5    {
   -> 6            printf("hello\n");
      7
      8            return 0;
      9    }
   Target 0: (iwasm) stopped.
   (lldb) br l
   Current breakpoints:
   1: name = 'main', locations = 2, resolved = 2, hit count = 2
     1.1: where = iwasm`main + 48 at main.c:294:11, address = 0x0000000100001020, resolved, hit count = 1
     1.2: where = JIT(0x100298004)`main + 12 at hello.c:6:9, address = 0x00000001002980a0, resolved, hit count = 1
   
   (lldb)

   • In the above example,

     • The first main function, which is in main.c, is the main function of the iwasm command.

     • The second main function, which is in hello.c, is the main function of the AOT-compiled wasm module.

   • WAMR AOT debugging uses the GDB JIT loader mechanism to load the debug info of the debugee module. On some platforms including macOS, you need to enable it explicitly. (settings set plugin.jit-loader.gdb.enable on)

     References:

     • https://github.com/llvm/llvm-project/blob/main/llvm/docs/DebuggingJITedCode.rst
     • https://sourceware.org/gdb/current/onlinedocs/gdb/JIT-Interface.html