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"debug-tools" sample introduction

Tool to symoblicate stack traces. When using wasm in production, debug info are usually stripped using tools like wasm-opt, to decrease the binary size. If a corresponding unstripped wasm file is kept, location information (function, file, line, column) can be retrieved from the stripped stack trace.

Build and run the sample

Generate the stack trace

Build iwasm with WAMR_BUILD_DUMP_CALL_STACK=1 and WAMR_BUILD_FAST_INTERP=0 and the wasm file with debug info (e.g. clang -g). As it is done in CMakeLists.txt and wasm-apps/CMakeLists.txt (look for addr2line):

$ mkdir build && cd build
$ cmake ..
$ make
$ ./iwasm wasm-apps/trap.wasm

The output should be something like

#00: 0x0159 - $f5
#01: 0x01b2 - $f6
#02: 0x0200 - $f7
#03: 0x026b - $f8
#04: 0x236b - $f15
#05: 0x011f - _start

Exception: unreachable

Copy the stack trace printed to stdout into a separate file (call_stack.txt):

$ ./iwasm wasm-apps/trap.wasm | grep "#" > call_stack.txt

Same for AOT. The AOT binary has to be generated using the --enable-dump-call-stack option of wamrc, as in CMakeLists.txt. Then run:

$ ./iwasm wasm-apps/trap.aot | grep "#" > call_stack.txt

Symbolicate the stack trace

Run the addr2line script to symbolicate the stack trace:

$ python3 ../../../test-tools/addr2line/addr2line.py \
    --wasi-sdk /opt/wasi-sdk \
    --wabt /opt/wabt \
    --wasm-file wasm-apps/trap.wasm \
    call_stack.txt

The output should be something like:

0: c
        at wasm-micro-runtime/samples/debug-tools/wasm-apps/trap.c:5:1
1: b
        at wasm-micro-runtime/samples/debug-tools/wasm-apps/trap.c:11:12
2: a
        at wasm-micro-runtime/samples/debug-tools/wasm-apps/trap.c:17:12
3: main
        at wasm-micro-runtime/samples/debug-tools/wasm-apps/trap.c:24:5
4: <unknown>
        at unknown:?:?
5: _start

If WAMR is run in fast interpreter mode (WAMR_BUILD_FAST_INTERP=1), addresses in the stack trace cannot be tracked back to location info. If WAMR <= 1.3.2 is used, the stack trace does not contain addresses. In those two cases, run the script with --no-addr: the line info returned refers to the start of the function

$ python3 ../../../test-tools/addr2line/addr2line.py \
    --wasi-sdk /opt/wasi-sdk \
    --wabt /opt/wabt \
    --wasm-file wasm-apps/trap.wasm \
    call_stack.txt --no-addr