使用emcc编译.c文件时会报错，但能正常生成.wasm文件并运行正常，请问如何消除错误提示。

[kamylee]

我在一个hello.c文件中申明了： int foo(int a, int b); void foo2(char * msg, char * buffer, int buf_len);

EMSCRIPTEN_KEEPALIVE int test2(char* strParam ,int iParam) { printf("p1:%s , p2:%d .\n",strParam,iParam);

int c = foo(3, 3);
printf("test2 add:%d .\n",c);

char * msg = "hello";
char buffer[100];
foo2(msg, buffer, sizeof(buffer));   // call into native foo2()
printf("test2 buffer:%s .\n",buffer);

return 1;
// return "from wasm test1 api";

}

使用命令：emcc -O3 hello.c -o hello.wasm -s STANDALONE_WASM --no-entry 不过可以正常运行输出结果：

error: undefined symbol: foo (referenced by top-level compiled C/C++ code) warning: Link with -sLLD_REPORT_UNDEFINEDto get more information on undefined symbols warning: To disable errors for undefined symbols use-sERROR_ON_UNDEFINED_SYMBOLS=0 warning: _foo may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library error: undefined symbol: foo2 (referenced by top-level compiled C/C++ code) warning: _foo2 may need to be added to EXPORTED_FUNCTIONS if it arrives from a system library Error: Aborting compilation due to previous errors 我要如何消除这个错误提示呢？

[lum1n0us]

IIUC, foo and foo2 are undefined symbols. what's your expectation on whole program?

[kamylee]

我要在c++中加载这个wasm。foo和foo2的申明放在wasm文件中，foo和foo2定义在c++本地，我想在使用emcc编译时能以正确的方式编译，并不会报错。我不确定是不是我的操作有什么问题。因为虽然能编译出wasm并能正常运行，但感觉不完善，因为他是报过错的。 我要怎么写这个wasm文件，能正常调用外部函数，并在编译时不会报错？感谢！

[lum1n0us]

in that case, callback is an example to start with. Please be aware of that, there is no need to prepare callback.wat. You should write a c++ program and use emcc to compile it to Wasm.

In C/C++, use import_name and import_module to declare a import function.