段故障,在c中分配给双指针 [英] segment fault, assigning to double pointer in c
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问题描述
关于如何为双指针正确分配内存,我有些困惑.
I am getting a little confused as to how to properly allocate memory for double pointers.
我的代码第二次尝试在第一个UCHAR指针数组的第二个索引处存储值时导致段错误.
My code causes a segment fault the second time it attempts to store a value at the 2nd index of the first UCHAR pointer array.
任何帮助将不胜感激.
分配我的双指针:
width = BMP_GetWidth (bmp);
height = BMP_GetHeight (bmp);
depth = BMP_GetDepth (bmp);
r = (UCHAR **) malloc(sizeof(UCHAR *) * height);
g = (UCHAR **) malloc(sizeof(UCHAR *) * height);
b = (UCHAR **) malloc(sizeof(UCHAR *) * height);
init_rgb(bmp, width, height, r, g, b);
试图利用指针(x = 1失败):
attempting to utilize the pointer (fails on x = 1):
void init_rgb(BMP *bmp, UINT w, UINT h, UCHAR **r, UCHAR **g, UCHAR **b) {
printf("%ld, %ld\n", w, h);
UINT x, y;
for (y = 0; y < h; y++) {
r[y] = (UCHAR *)malloc(sizeof(UCHAR) * w);
for (x = 0; x < w; x++) {
BMP_GetPixelRGB(bmp, x, y, &r[y][x], &g[y][x], &b[y][x]);
printf("FAILING After First Iteration\n");
}
}
}
推荐答案
看起来您需要像这样的行
Looks like you need a line like
r[y] = (UCHAR *)malloc(sizeof(UCHAR) * w);
用于 g
和 b
.如果你不这样做,g[y]
和 b[y]
是未定义的.当您引用这些代码时,您的代码可能会失败.
for g
and b
as well. If you don't do that, g[y]
and b[y]
are undefined. Your code is probably failing when you reference those.
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