Question

这个简短的C ++程序表现得让我困惑：

HANDLE hStdErrRd = NULL;
HANDLE hStdErrWr = NULL;

SECURITY_ATTRIBUTES saAttr = {0};
saAttr.nLength = sizeof(SECURITY_ATTRIBUTES); 
saAttr.bInheritHandle = TRUE; 
saAttr.lpSecurityDescriptor = NULL; 

if (!CreatePipe(&hStdErrRd, &hStdErrWr, &saAttr, 0)) {
    // error handling
}
if (!SetHandleInformation(hStdErrRd, HANDLE_FLAG_INHERIT, 0)) {
    // error handling
}

String CmdLine = "\"C:\\path to\\java.exe\" -jar \"C:\\path to\\decompile.jar\" -o Source/ \"C:\\path to\\file.jar\"";

STARTUPINFO si = {0};
si.cb = sizeof(si);
si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
si.hStdInput = GetStdHandle(STD_INPUT_HANDLE);
si.hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
si.hStdError = hStdErrWr;
si.wShowWindow = SW_HIDE;

PROCESS_INFORMATION pi = {0};

if (CreateProcess(NULL, CmdLine.c_str(), NULL, NULL, TRUE, CREATE_NO_WINDOW, NULL, NULL, &si, &pi))
{
    CloseHandle(pi.hThread);
    CloseHandle(pi.hProcess);

    // must close our handle to the write-side of the pipe so the pipe will close
    // when the child process terminates so ReadFile() will know to stop expecting data...
    CloseHandle(hStdErrWr);

    AnsiString output;
    char buffer[1024];
    DWORD dwBytesRead;

    while (ReadFile(hStdErrRd, buffer, sizeof(buffer), &dwBytesRead, NULL))
    {
        if (dwNumRead == 0)
            break;

        output += AnsiString(buffer, dwBytesRead);
        do
        {
            int pos = output.Pos("\n");
            if (pos == 0)
                break;

            Memo1->Lines->Add(output.SubString(1, pos-1).TrimRight());
            output.Delete(1, pos);
        }
        while (!output.IsEmpty());
    }

    if (!output.IsEmpty())
        Memo1->Lines->Add(output.TrimRight());
}
else
{
    // error handling

    CloseHandle(hStdErrWr);
}

CloseHandle(hStdErrRd);

使用#include <cassert> #include <iostream> #include <string> #include <boost/lexical_cast.hpp> int main(void) { signed char c = -2; assert(c == -2); c = boost::lexical_cast<signed char>(std::string("-2")); std::cout << c << "\n"; }和g++ 5.2.1，我得到：

在抛出'boost :: exception_detail :: clone_impl＆gt;'的实例后终止调用 what（）：错误的词法转换：源类型值无法解释为目标

为什么不能将字符串“-2”中的强制转换为boost-1.58.0，因为此类型可以表示值signed char？

Answer 1

解决方案是使用Boost：

#include <boost/lexical_cast.hpp>
#include <boost/numeric/conversion/cast.hpp>
int tmp = boost::lexical_cast<int>(std::string("-2"));
char c = boost::numeric_cast<signed char>(tmp);

boost :: lexical_cast <signed char =“”>无法处理负数？

1 个答案: