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分类: C/C++
2008-10-11 16:46:07
void f1(char *explanation)
{
char p1;
p1 = malloc(100);
(void) sprintf(p1,
"The f1 error occurred because of '%s'.",
explanation);
local_log(p1);
}
int getkey(char *filename)
{
FILE *fp;
int key;
fp = fopen(filename, "r");
fscanf(fp, "%d", &key);
return key;
}
清单 3. 未初始化的指针
void f2(int datum)
{
int *p2;
/* Uh-oh! No one has initialized p2. */
*p2 = datum;
...
}
/* Allocate once, free twice. */
void f3()
{
char *p;
p = malloc(10);
...
free(p);
...
free(p);
}
/* Allocate zero times, free once. */
void f4()
{
char *p;
/* Note that p remains uninitialized here. */
free(p);
}
void f8()
{
struct x *xp;
xp = (struct x *) malloc(sizeof (struct x));
xp.q = 13;
...
free(xp);
...
/* Problem! There's no guarantee that
the memory block to which xp points
hasn't been overwritten. */
return xp.q;
}
/********
* ...
*
* Note that any function invoking protected_file_read()
* assumes responsibility eventually to fclose() its
* return value, UNLESS that value is NULL.
*
********/
FILE *protected_file_read(char *filename)
{
FILE *fp;
fp = fopen(filename, "r");
if (fp) {
...
} else {
...
}
return fp;
}
/*******
* ...
*
* Note that the return value of get_message points to a
* fixed memory location. Do NOT free() it; remember to
* make a copy if it must be retained ...
*
********/
char *get_message()
{
static char this_buffer[400];
...
(void) sprintf(this_buffer, ...);
return this_buffer;
}
/********
* ...
* While this function uses heap memory, and so
* temporarily might expand the over-all memory
* footprint, it properly cleans up after itself.
*
********/
int f6(char *item1)
{
my_class c1;
int result;
...
c1 = new my_class(item1);
...
result = c1.x;
delete c1;
return result;
}
/********
* ...
* Note that f8() is documented to return a value
* which needs to be returned to heap; as f7 thinly
* wraps f8, any code which invokes f7() must be
* careful to free() the return value.
*
********/
int *f7()
{
int *p;
p = f8(...);
...
return p;
}
static char *important_pointer = NULL;
void f9()
{
if (!important_pointer)
important_pointer = malloc(IMPORTANT_SIZE);
...
if (condition)
/* Ooops! We just lost the reference
important_pointer already held. */
important_pointer = malloc(DIFFERENT_SIZE);
...
}
int main()
{
char p[5];
strcpy(p, "Hello, world.");
puts(p);
}
chinaunix网友2008-10-16 16:12:12
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