[英]dereferencing ‘void *’ pointer in C
所以我把那些放在.h中
stable.h
// The symbol table.
typedef struct stable_s *SymbolTable;
// Data stored.
typedef union {
int i;
char *str;
void *p;
} EntryData;
// Return struct for stable_insert.
typedef struct {
int new; // Was a new entry created?
EntryData *data; // Data associated with entry.
} InsertionResult;
etc
然后在我的.c
stable.c
etc
typedef struct {
char *key;
EntryData data;
} Entry;
struct stable_s { /* Indice hash */
char index;
int size;
void *pointer;
};
etc
EntryData *stable_find(SymbolTable table, const char *key){
int k;
char c;
if (key[0] >= 'A' && key[0] <= 'Z')
c = table[(key[0] - 65)].index;
else if (key[0] >= 'a' && key[0] <= 'z')
c = table[(key[0] - 141)].index;
else
c = table[26].index;
c -= 65;
if (table[c].size == 0)
return NULL;
k = busca_binaria(table[c].pointer, table[c].size, key);
if (strcmp(table[c]->pointer[k]->key, key) == 0)
return table[c]->pointer[k]->data;
return NULL;
}
而gcc -std=c99 stable.c -o stable
給了我這些錯誤:
stable2.c: In function 'stable_find': stable2.c:128:24: error: invalid type argument of '->' (have 'struct stable_s') if (strcmp(table[c]->pointer[k]->key, key) == 0) stable2.c:129:24: error: invalid type argument of '->' (have 'struct stable_s') return table[c]->pointer[k]->data;
我想念什么? 我真的迷上了語法。
讓我們看一下這些行:
k = busca_binaria(table[c].pointer, table[c].size, key);
if (strcmp(table[c]->pointer[k]->key, key) == 0)
return table[c]->pointer[k]->data;
什么是table
? 是struct stable_s *
所以
table[c]
是一個struct stable_s
-它不是指針。
所以回到行:
k = busca_binaria(table[c].pointer, table[c].size, key);
^^^^^^^^^^^^^^^^
Correct as table[c] is a struct stable_s
if (strcmp(table[c]->pointer[k]->key, key) == 0)
^^^^^^^^^^^^^^^^^^^^
Wrong as table[c] is not a point
return table[c]->pointer[k]->data;
^^^^^^^^^^^^^^^^^^^^
Wrong as table[c] is not a point
您的代碼中似乎還有其他問題(例如,對`void *的取消引用),但以上問題應與編譯器錯誤有關。
也許這行:
if (strcmp(table[c]->pointer[k]->key, key) == 0)
應該:
if (strcmp(((Entry*)table[c].pointer)[k].key, key) == 0)
但是我不確定,因為您還沒有發布說明這一點的代碼。
也許這行:
return table[c]->pointer[k]->data;
應該:
return &(((Entry*)table[c].pointer)[k].data);
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