'uintmax_t'到'size_t'和'unsigned int'转换的数据丢失是多少？ [英] What is the loss of data in 'uintmax_t' to 'size_t' and 'unsigned int' conversion?

问题描述

我明白了：

警告C4244：'初始化'：从'uintmax_t'转换为'unsigned int'，可能会丢失数据

warning C4244: 'initializing' : conversion from 'uintmax_t' to 'unsigned int', possible loss of data

on：

boost::shared_array<char> buffer( new char[file->size]);

...然后这个：

警告C4244：'参数'：从'uintmax_t'转换为'size_t'，可能丢失数据

warning C4244: 'argument' : conversion from 'uintmax_t' to 'size_t', possible loss of data

on：

boost::asio::write(*socket, boost::asio::buffer(buffer.get(), file->size));

我会害怕还是没事？

推荐答案

可能 file-> size 的类型为 uintmax_t 大于 size_t ，运算符new [] 占用数组大小​​。通常，第一个可能是64位整数，而第二个只能是32位。

Probably file->size is of type uintmax_t which is larger than the size_t that operator new[] takes for the array size. Typically the first one could be a 64bit integer while the second one would only be a 32bit.

实际上，当您尝试处理超过4GB的文件时，这会导致问题，因为 size_t 不能代表如此大量的字节。如果您只希望处理较小的文件，其中 size_t 足以存储文件大小，则不会出现问题。

Practically this will lead to problems when you are trying to handle files over 4GB, because the size_t can't represent such a large number of bytes. If you only expect to handle smaller files where size_t is large enough to store the file size, there won't be a problem.

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