Question

当我尝试将以下代码段编译成WebAssembly二进制文件时，我不断发出unresolved symbol: llvm_trap警告，这使得wasm代码无法从JS中获取。

emcc test.c -s WASM=1 -s ONLY_MY_CODE=1 -s "EXPORTED_FUNCTIONS=['_test']" -O2 -g -o test.js

test.c （这是在没有做有意义的工作的情况下重现问题的测试代码。）

int test(int *buf) {
  int C = 1;
  // Assuming WebAssembly.Memory buffer has been preloaed with data. 
  // *T represents the preloaded data here. And We know *T and *buf 
  // won't overlap in memory.
  int *T = 0; 

  int index = C ^ buf[5];
  int right = T[index];
  int left = (unsigned)C >> 8;

  // warning disappears if this is commented out. But why?
  C = left ^ right; 

  return C;
}

我没有写任何llvm_trap相关代码。有人有想法是什么意思吗？

Answer 1

必须初始化变量T。如果它代表一个映射＆＃39;映射＆＃39;对于WebAssembly线性存储器，您可以将其定义为全局，如下所示：

int T[1000];

int test(int *buf) {
  int C = 1;

  int index = C ^ buf[5];
  int right = T[index];
  int left = (unsigned)C >> 8;

  // warning disappears if this is commented out. But why?
  C = left ^ right;

  return C;
}

编译时没有llvm_trap警告。

有关如何使用线性内存将数据传递到WASM函数的更多详细信息，请参阅以下问题：

How to access WebAssembly linear memory from C/C++

未解决的符号：来自Emscripten的llvm_trap

1 个答案: