我正在研究一个c代码,它包含一个托管一些我称之为范围的值的结构。
我的目的是动态地使用这个所谓的范围(每次执行时保存不同数量的数据)。我现在暂时使用#define comp代替。每次通过使用s1结构(和内存分配)调用update_range时,这个所谓的范围都会更新。
我发现奇怪的是,当我介绍一个" show_range"函数输出更新函数内部/外部的实际值我意识到我松了前两个值。 这是代码。 有什么建议吗? 提前谢谢!
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <errno.h>
#include <string.h>
#include <complex.h>
#define comp 1024
// struct holding a complex-valued range
struct range {
int dimensions; /* number of dimensions */
int* size; /* array holding number of points per dimension */
complex double* values; /* array holding complex valued */
int components; /* number of components that will change on any execution*/
};
// parameters to use in function
struct s1 {
int tag;
struct range* range;
};
int update_range(struct s1* arg);
int show_range(struct range* argrange, char* message);
int copy_range(struct range* in, struct range* out);
int main(void) {
int ret = 0;
struct s1 s1;
s1.tag = 0;
s1.range = malloc(sizeof(struct range));
update_range(&s1);
show_range(s1.range, "s1.range inside main function");
return ret;
}
////////////////////////////////////////////
int update_range(struct s1* arg) {
int ret = 0;
int i;
struct range range;
range.dimensions = 1;
range.size = malloc(range.dimensions * sizeof(int));
range.components = comp;
range.size[0] = range.components; // unidimensional case
range.values = malloc(range.components * sizeof(complex double));
for (i = 0; i < range.components; i++) {
range.values[i] = (i + 1) + I * (i + 1);
}
show_range(&range, "range inside update_range function");
arg->range->size =
malloc(range.dimensions * sizeof(int)); // size was unknown before
arg->range->values =
malloc(comp * sizeof(complex double)); // amount of values was unknown
copy_range(&range, arg->range);
show_range(arg->range, "arg->range inside update_range function");
if (range.size)
free(range.size);
range.size = NULL;
if (range.values)
free(range.values);
range.values = NULL;
return ret;
}
////////////////////////////////////////////
// Show parameters (10 first values)
int show_range(struct range* argrange, char* message) {
int ret = 0;
vint i;
printf(" ******************************\n");
printf(" range in %s \n", message);
printf(" arg.dimensions=%d \n", argrange->dimensions);
printf(" arg.size[0]=%d \n", argrange->size[0]);
printf(" argrange.components=%d \n", argrange->components);
printf(" first 10 {Re} values: \n");
for (i = 0; i < 10; i++) {
printf(" argrange.values[%d]=%f\n", i, creal(argrange->values[i]));
}
printf("\n");
return ret;
}
////////////////////////////////////////////
// copy range
int copy_range(struct range* in, struct range* out) {
int ret = 0;
if (in == NULL) {
fprintf(stderr, "error: in points to NULL (%s:%d)\n", __FILE__,
__LINE__);
ret = -1;
goto cleanup;
}
if (out == NULL) {
fprintf(stderr, "error: out points to NULL (%s:%d)\n", __FILE__,
__LINE__);
ret = -1;
goto cleanup;
}
out->dimensions = in->dimensions;
out->size = in->size;
out->values = in->values;
out->components = in->components;
cleanup:
return ret;
}
答案 0 :(得分:1)
你的copy_range函数被破坏了,因为它只复制指向大小和值的指针而不是内存。在您调用free(range.size);
和free(range.values);
之后,您也会从原始对象中删除mamory,但不将其指针设置为NULL。
调用update_range后,s1.range在大小和值上都有非NULL指针,但它们指向已删除的内存。
答案 1 :(得分:0)
由于访问释放的内存,您遇到了未定义的行为(UB)。您的copy_range()
函数只会对两个指针字段执行浅表复制,因此当您运行free(range->size)
时,您arg->range->size
无效。
您应该通过分配和复制指针内容来使copy_range()
成为深层副本,如:
out->size = malloc(in->dimensions * sizeof(int));
memcpy(out->size, in->size, in->dimensions * sizeof(int));
out->values = malloc(in->components * sizeof(complex double));
memcpy(out->values , in->values, in->components * sizeof(complex double));
答案 2 :(得分:0)
There are not 10 items to print, so the lines:
printf(" first 10 {Re} values: \n");
for (i = 0; i < 10; i++) {
printf(" argrange.values[%d]=%f\n", i, creal(argrange->values[i]));
}
Will be printing from random memory.
a much better method would be:
printf(" first %d {Re} values: \n", min(argrange.components,10));
for (i = 0; i < argrange.components; i++) {
printf(" argrange.values[%d]=%f\n", i, creal(argrange->values[i]));
}
The above is just one of many problems with the code.
I would suggest executing the code using a debugger to get the full story.
as it is, the code has some massive memory leaks due mostly
to overlaying malloc'd memory pointers.
for instance as in the following:
arg->range->size =
malloc(range.dimensions * sizeof(int)); // size was unknown before
arg->range->values =
malloc(comp * sizeof(complex double)); // amount of values was unknown