如何将llvm :: outs()重定向到文件? [英] How to redirect llvm::outs() to file?

问题描述

我正在使用一些LLVM工具(例如 llvm-nm )作为静态库.IE.我复制了源llvm-nm.cpp，将 main(..)重命名为 llvm_nm(..)，并将其编译为静态库.我想将标准输出转发到我的文件.

I'm using some LLVM tools (like llvm-nm) as static libraries. I.e. i copied source llvm-nm.cpp, renamed main(..) to llvm_nm(..) and compiled it as static library. I'd like to forward standard output to my file.

我尝试使用下一种方法:

I've tried to use the next approach:

  int    out_fd, err_fd;
  fpos_t out_pos, err_pos;

  // redirect out
  fflush(stdout);
  fgetpos(stdout, &out_pos);
  out_fd = dup(fileno(stdout));
  freopen(outFilename, "w", stdout);

  // execute
  int ret = llvm_nm(argc_, argv_);

  // restore output
  fflush(stdout);
  dup2(out_fd, fileno(stdout));
  close(out_fd);
  clearerr(stdout);
  fsetpos(stdout, &out_pos); 

问题是它没有被转发(如果我在nm源代码中添加 printf()而不是 nm 输出，则可以正常工作).我已经看过源了，我可以看到使用 llvm :: outs() stream:

The problem is that it's not forwarded (it works if i add printf() in nm source code but not for nm output). I've looke to the source and i can see output is done using llvm::outs() stream:

outs() << "Archive map" << "\n";

并且已实现的另一种方式:

/// outs() - This returns a reference to a raw_ostream for standard output.
00702 /// Use it like: outs() << "foo" << "bar";
00703 raw_ostream &llvm::outs() {
00704   // Set buffer settings to model stdout behavior.
00705   // Delete the file descriptor when the program exits, forcing error
00706   // detection. If you don't want this behavior, don't use outs().
00707   static raw_fd_ostream S(STDOUT_FILENO, true);
00708   return S;
00709 }

如何将输出重定向到我的文件?

How can i redirect that output to my file?

推荐答案

我意识到这是一个老问题，但是，我偶然发现它为llvm的outs()流查找了一些简单的信息，而我发现这里.

I realize this is an old question, however, I came across it looking up some simple information for llvm's outs() stream which I found here.

llvm"BrainF"随附的示例之一使用它的方式是这样的:

One of the examples that comes with llvm "BrainF" uses it like this:

  ...

  raw_ostream *out = &outs();
  if (!JIT) {
    if (OutputFilename == "") {
      std::string base = InputFilename;
      if (InputFilename == "-") { base = "a"; }

      // Use default filename.
      OutputFilename = base+".bc";
    }
    if (OutputFilename != "-") {
      std::error_code EC;
      out = new raw_fd_ostream(OutputFilename, EC, sys::fs::F_None);
    }
  }

  ...

  if (out != &outs())
    delete out;

  ...

所以这似乎表明您可以安全地重定向.

So it seems to suggest that you are safe to redirect.

注意:在本示例中，OutputFilename/InputFilename是使用llvm的支持库 查看全文