Uncaught TypeError: Cannot read properties of undefined (reading 'length')

[Flyingbeanss]

Hi! I want to deal with memory access out of bound in my program. After I add set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address") and set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -fsanitize=address") , the console print as follow:

Uncaught TypeError: Cannot read properties of undefined (reading 'length')
    at lengthBytesUTF8 (occt-webgl-sample.js?t=1700141293680:1746:26)
    at stringToNewUTF8 (occt-webgl-sample.js?t=1700141293680:5971:13)
    at occt-webgl-sample.js?t=1700141293680:10523:32
    at withBuiltinMalloc (occt-webgl-sample.js?t=1700141293680:5962:10)
    at _emscripten_pc_get_file (occt-webgl-sample.js?t=1700141293680:10519:37)
    at occt-webgl-sample.wasm.__sanitizer::EmscriptenSymbolizerTool::SymbolizePC(unsigned long, __sanitizer::SymbolizedStack*) (occt-webgl-sample.wasm:0x16a5673)
    at occt-webgl-sample.wasm.__sanitizer::Symbolizer::SymbolizePC(unsigned long) (occt-webgl-sample.wasm:0x16a5960)
    at occt-webgl-sample.wasm.__lsan::LeakSuppressionContext::GetSuppressionForAddr(unsigned long) (occt-webgl-sample.wasm:0x1696920)
    at occt-webgl-sample.wasm.__lsan::LeakSuppressionContext::Suppress(unsigned int, unsigned long, unsigned long) (occt-webgl-sample.wasm:0x1696a6b)
    at occt-webgl-sample.wasm.__lsan::LeakReport::ApplySuppressions() (occt-webgl-sample.wasm:0x1697c0f)

I just don't understand why.
Here is the original output.

occt-webgl-sample.js?t=1700142325331:14608 Uncaught RuntimeError: memory access out of bounds
    at occt-webgl-sample.wasm.math_FunctionSetRoot::math_FunctionSetRoot(math_FunctionSetWithDerivatives&, math_Vector const&, int) (occt-webgl-sample.wasm:0xa28b01)
    at invoke_iiiii (occt-webgl-sample.js?t=1700142325331:14605:36)
    at occt-webgl-sample.wasm.math_FunctionRoot::math_FunctionRoot(math_FunctionWithDerivative&, double, double, double, double, int) (occt-webgl-sample.wasm:0xa261a0)
    at occt-webgl-sample.wasm.Extrema_LocEPCOfLocateExtPC::Perform(gp_Pnt const&, double) (occt-webgl-sample.wasm:0x8a659a)
    at invoke_viid (occt-webgl-sample.js?t=1700142325331:14990:29)
    at occt-webgl-sample.wasm.Extrema_LocateExtPC::Perform(gp_Pnt const&, double) (occt-webgl-sample.wasm:0x8a56ff)
    at invoke_viid (occt-webgl-sample.js?t=1700142325331:14990:29)
    at occt-webgl-sample.wasm.Extrema_LocateExtPC::Extrema_LocateExtPC(gp_Pnt const&, Adaptor3d_Curve const&, double, double, double, double) (occt-webgl-sample.wasm:0x8a62af)
    at invoke_iiiidddd (occt-webgl-sample.js?t=1700142325331:16343:36)
    at occt-webgl-sample.wasm.ShapeAnalysis_Curve::ProjectAct(Adaptor3d_Curve const&, gp_Pnt const&, double, gp_Pnt&, double&) const (occt-webgl-sample.wasm:0x4957fd)

Thanks for help , sincerely!

[sbc100]

Hmm.. it looks like convertPCtoSourceLocation must be returning a result that doesn't have a .file attribute so undefined is being passed to stringToNewUTF8 here:

emscripten/src/library.js

Line 2819 in 9429b48

_emscripten_pc_get_file.ret = stringToNewUTF8(result.file);

Strange that we have never seen this before.

Can you try adding -g and/or --profiling-funcs to your compile and link flags?

[Flyingbeanss]

@sbc100 Thanks for reply. Actually, I have added set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -g") and set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -g"). After I add set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} --profiling-funcs") and set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} --profiling-funcs"), it seems to be no change in the console.

[sbc100]

Can you take look devtools a few levels up the stack in emscripten_pc_get_file? Can you see what result contains? (The thing that convertPCtoSourceLocation returns?)

[Flyingbeanss]

@sbc100 Thanks for your advice. I'm not very familiar with js and browser.

 var result = convertPCtoSourceLocation(pc);
 if (!result) return 0;

convertPCtoSourceLocation(pc); returns null

[sbc100]

When the crash happens though I'm pretty such it doesn't return null, since it does not return there but goes on to call stringToNewUTF8 below. You need to somehow pause/break when the exceptions happens. Try "Pause on exceptions" in devtools.

Then select the emscripten_pc_get_file and type result in the console to see its contents (or inspect it using the Locals pane).

[Flyingbeanss]

Thank you for being so patient.I make a mistake, it's not null. The convertPCtoSourceLocation(pc); will be called many times.After a certain call, it returns undefined.The content is here:

[tovabar]

Hi @sbc100,
I have the same problem in the following case:
I compiled with:
set(CMAKE_CXX_FLAGS "-gsource-map -fsanitize=address -fsanitize-recover=address ${CMAKE_CXX_FLAGS}")
set(CMAKE_C_FLAGS "-gsource-map -fsanitize=address -fsanitize-recover=address ${CMAKE_C_FLAGS}")
and link flags:
-O2 -gsource-map -fsanitize=address -fsanitize-recover=address -sMODULARIZE -sEXPORT_NAME=McStartMyProj -sERROR_ON_UNDEFINED_SYMBOLS=0 -sWARN_ON_UNDEFINED_SYMBOLS=0 --pre-js WrapperUtils.js -lnodefs.js -lembind --embed-file FS -sGL_ENABLE_GET_PROC_ADDRESS=1 -sMIN_WEBGL_VERSION=1 -sMAX_WEBGL_VERSION=2 -sSTACK_SIZE=5MB -sALLOW_MEMORY_GROWTH=1 -sINITIAL_HEAP=1GB -sMAXIMUM_MEMORY=4GB -sMEMORY_GROWTH_GEOMETRIC_STEP=0.5 -sMEMORY_GROWTH_GEOMETRIC_CAP=0 (optimization with -O2 is a must in my case, due to another limitation)

all ASan checks work properly, but once __lsan::DoRecoverableLeakCheckVoid() is invoked manually for runtime memory leak detection, the following error is emitted:

MyProj_D.js:3251 Uncaught TypeError: Cannot read properties of undefined (reading 'length')
    at lengthBytesUTF8 (MyProj_D.js:3251:27)
    at stringToNewUTF8 (MyProj_D.js:8283:14)
    at MyProj_D.js:13853:33
    at withBuiltinMalloc (MyProj_D.js:8274:12)
    at _emscripten_pc_get_file (MyProj_D.js:13848:37)
    at MyProj_D.wasm.__sanitizer::EmscriptenSymbolizerTool::SymbolizePC(:3000/unsigned long, __sanitizer::SymbolizedStack*) (http://localhost:3000/MyProj_D.wasm)
    at MyProj_D.wasm.__sanitizer::Symbolizer::SymbolizePC(:3000/unsigned long) (http://localhost:3000/MyProj_D.wasm)
    at MyProj_D.wasm.__lsan::LeakSuppressionContext::GetSuppressionForAddr(:3000/unsigned long) (http://localhost:3000/MyProj_D.wasm)
    at MyProj_D.wasm.__lsan::LeakSuppressionContext::Suppress(:3000/unsigned int, unsigned long, unsigned long) (http://localhost:3000/MyProj_D.wasm)
    at MyProj_D.wasm.__lsan::CheckForLeaks(:3000/) (http://localhost:3000/MyProj_D.wasm)

as u mentioned before, result.file is undefined calling to convertPCtoSourceLocation from _emscripten_pc_get_file
do u have an idea what can be done to resolve this?

[stevenwdv]

Hi, I also have this problem (with address sanitizer + source map), with all result fields being undefined.

It seems that WasmSourceMap allows all info fields to be optional:

emscripten/src/source_map_support.js

Lines 49 to 56 in d1f88fa

	var info = {};
	offset += data[0];
	if (data.length >= 2) info.source = src += data[1];
	if (data.length >= 3) info.line = line += data[2];
	if (data.length >= 4) info.column = col += data[3];
	if (data.length >= 5) info.name = name += data[4];
	this.mapping[offset] = info;

Contrary, functions like emscripten_pc_get_file assume they are always set if the result is not null (except for emscripten_pc_get_column, apparently, which has result.column || 0).