如何解決此 sysmalloc 斷言：
main: malloc.c:2542: sysmalloc: 斷言`(old_top == initial_top (av) && old_size == 0) || ((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top) && ((unsigned long) old_end & (pagesize - 1)) == 0)' 失敗。
我是否在 Valgrind 參考的 2 個函式（即set_slice_array()和print_int()）中犯了一些明顯的與記憶體相關的錯誤？
在做了一些研究之后，似乎我看到的錯誤可能是由于我在過去分配的堆上覆寫了一些記錄（malloc 需要的）。但我仍在學習 C 中動態記憶體分配的技巧，所以我不確定如何解決這個問題。
通過 Valgrind 運行我的程式，給了我以下資訊（以及關于“無效寫入”和“無效讀取”的兩個提示）：
==2328== **Invalid write of size 2**
==2328== at 0x48452E3: memmove (in /nix/store/7p3q3hn63ya4c46swsxlbmy03sbxz3d9-valgrind-3.16.1/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2328== by 0x4019FB: set_slice_array (main.c:44)
==2328== by 0x4019FB: extend_slice (main.c:97)
==2328== by 0x4019FB: join_slices (main.c:107)
==2328== by 0x4019FB: main (main.c:124)
==2328== Address 0x4a14698 is 0 bytes after a block of size 40 alloc'd
==2328== at 0x4840B68: realloc (in /nix/store/7p3q3hn63ya4c46swsxlbmy03sbxz3d9-valgrind-3.16.1/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2328== by 0x40189D: grow_dynamic_array (main.c:29)
==2328== by 0x40189D: set_slice_array (main.c:41)
==2328== by 0x40189D: new_slice_from_array (main.c:59)
==2328== by 0x40189D: main (main.c:118)
==2328==
==2328== **Invalid read of size 4**
==2328== at 0x401B59: print_int (main.c:65)
==2328== by 0x401B59: print_slice (main.c:71)
==2328== by 0x401B59: debug_slice (main.c:86)
==2328== by 0x401B59: main (main.c:125)
==2328== Address 0x4a14698 is 0 bytes after a block of size 40 alloc'd
==2328== at 0x4840B68: realloc (in /nix/store/7p3q3hn63ya4c46swsxlbmy03sbxz3d9-valgrind-3.16.1/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==2328== by 0x40189D: grow_dynamic_array (main.c:29)
==2328== by 0x40189D: set_slice_array (main.c:41)
==2328== by 0x40189D: new_slice_from_array (main.c:59)
==2328== by 0x40189D: main (main.c:118)
==2328==
==2328==
==2328== HEAP SUMMARY:
==2328== in use at exit: 168 bytes in 5 blocks
==2328== total heap usage: 9 allocs, 4 frees, 1,252 bytes allocated
==2328==
==2328== LEAK SUMMARY:
==2328== definitely lost: 88 bytes in 3 blocks
==2328== indirectly lost: 80 bytes in 2 blocks
==2328== possibly lost: 0 bytes in 0 blocks
==2328== still reachable: 0 bytes in 0 blocks
==2328== suppressed: 0 bytes in 0 blocks
參考下面的代碼（in main.c），我試圖在 C 中實作 Go 的“切片”資料結構：
#include <stdio.h>
#include <stdlib.h>
typedef char byte;
typedef struct dynamic_array {
size_t capacity;
size_t item_size;
byte *data;
} dynamic_array;
typedef struct slice {
size_t start;
size_t length;
void (*print_func)(void *);
dynamic_array *array;
} slice;
dynamic_array *new_dynamic_array(capacity, item_size) {
dynamic_array *this = malloc(sizeof(dynamic_array));
this->capacity = capacity;
this->item_size = item_size;
this->data = malloc(capacity * item_size * sizeof(byte));
return this;
}
void grow_dynamic_array(dynamic_array *da, size_t length_needed) {
da->capacity = length_needed;
da->data = realloc(da->data, length_needed * sizeof(byte) * da->item_size);
}
void *get_slice_ptr(slice this) {
return (this.array->data (this.start * this.array->item_size));
}
slice set_slice_array(slice this, void *array, size_t capacity) {
dynamic_array *da = this.array;
size_t capacity_required = capacity;
while (capacity_required >= da->capacity) {
grow_dynamic_array(da, 2 * capacity_required);
}
memcpy(get_slice_ptr(this), array, da->item_size * capacity); // Culprit?
this.length = capacity;
return this;
}
slice new_slice(size_t capacity, size_t item_size, void (*print_func_ptr)(void *)) {
slice this;
this.start = this.length = 0;
this.print_func = print_func_ptr;
this.array = new_dynamic_array(capacity, item_size);
return this;
}
slice new_slice_from_array(void *array, size_t capacity, size_t item_size, void (*print_func_ptr)(void *)) {
slice this = new_slice(capacity, item_size, print_func_ptr);
this = set_slice_array(this, array, capacity);
return this;
}
void print_int(void *data_item) {
int value;
memcpy(&value, data_item, sizeof(int));
printf("[%d] ", value);
}
void print_slice(slice this) {
for (size_t i = this.start; i < this.start this.length; i) {
this.print_func(this.array->data (i * this.array->item_size));
}
printf("\n");
}
void debug_slice(slice this) {
dynamic_array da = *this.array;
printf("Length: %ld\nStart: %ld\nArray: %p\nCapacity: %ld\nItem_size: %ld\nData: %p\n",
this.length,
this.start,
(void *) this.array,
da.capacity,
da.item_size,
(void *) da.data
);
print_slice(this);
}
slice sub_slice(slice source, size_t sub_start, size_t sub_length) {
slice portion = source;
portion.start = source.start sub_start;
portion.length = sub_length;
return portion;
}
slice extend_slice(slice this, const void *item, size_t count) {
slice extension = set_slice_array(sub_slice(this, this.length, 0), item, count);
this.length = this.length extension.length;
return this;
}
slice append_slice(slice this, const void *item) {
return extend_slice(this, item, 1);
}
slice join_slices(slice base, slice extension) {
return extend_slice(base, get_slice_ptr(extension), extension.length);
}
int main(void) {
int test_array_ints[] = { 1, 2, 3, 4, 5 };
// First slice & debug print
slice test_slice1 = new_slice_from_array(&test_array_ints, 5, sizeof(int), print_int);
debug_slice(test_slice1);
printf("\n"); // Second slice & debug print
slice test_slice2 = new_slice_from_array(&test_array_ints, 5, sizeof(int), print_int);
int to_add = 6;
test_slice2 = append_slice(test_slice2, &to_add); // One culprit?
debug_slice(test_slice2);
printf("\n"); // Merge the 2 slices and then debug print
test_slice2 = join_slices(test_slice2, test_slice1);
debug_slice(test_slice2);
printf("\n"); // Create a third slice (which triggers the assert)
slice test_slice3 = new_slice_from_array(&test_array_ints, 5, sizeof(int), print_int);
return 0;
}
任何幫助將非常感激！
uj5u.com熱心網友回復：
size_t capacity_required = capacity; memcpy(get_slice_ptr(this),
好吧，決定 - 要么capacity_required是包含 的容量this.start，要么capacity_required是整個容量并且您要復制到this.array->data.
size_t capacity_required = capacity this.start;
memcpy(get_slice_ptr(this),
要么
size_t capacity_required = capacity;
this.start = 0;
memcpy(this.array->data,
取決于具體set_slice_array應該做什么。它應該重新分配和替換底層存盤中的元素，還是應該將切片“設定”到一個區域并重新構造切片？我不知道，沒有評論。
回圈while (capacity_required >= da->capacity)很奇怪，這是一個if. 無論如何，我會把它移到if里面grow_dynamic_array。
轉載請註明出處，本文鏈接：https://www.uj5u.com/caozuo/430163.html