为三重指针分配内存 [英] Allocating memory for triple pointer

问题描述

函数somefunction()以三重指针作为参数.

The function somefunction() takes a triple pointer as an argument.

int somefunction(tchar ***returnErrors);

如何为returnErrors参数分配内存?

推荐答案

正在猜测. .

您可以将returnErrors视为指向字符串数组的指针.

You can think of returnErrors as a pointer to an array of strings.

1. 第一个*实现指向数组的指针 tchar(或单个字符串) tchars)
2. 第二个*实现指向 字符串数组.
3. 最后一个*是，因此您可以更改 returnErrors并传回新的 记忆.

1. The first * imples pointer to array of tchar (or a single string of tchars)
2. The second * imples a pointer to an array of strings.
3. The last * is so you can change returnErrors and pass back the new memory.

为此目的分配内存(愚蠢的示例，在SomeFunction内部分配内存)

To delare memory for this (silly example, allocating memory inside SomeFunction)

tchar ** errors;
// Oops it appears I need to pass back two error strings (+ 1 for null on end, so we know there are no more - thanks tlholaday)
errors = malloc(sizeof(tchar*) * 3);

// the first string has length 20 (+ 1 for null terminator)
errors[0] = malloc(sizeof(tchar) * 21);

// the second string has length 30 (+ 1 for null terminator)
errors[1] = malloc(sizeof(tchar) * 31);

// ensure the last is null
errors[2] = 0;

*returnErrors = errors;

注意:调用函数需要知道SomeFunction已分配了内存并需要释放它.

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