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What is the argument for printf that formats a long?
... Yep Dr Beco; further, just %l triggers warning: unknown conversion type character 0x20 in format [-Wformat]
– Patrizio Bertoni
Jul 29 '15 at 10:53
add a comment
...
了解 Boost Filesystem Library - C/C++ - 清泛网 - 专注C/C++及内核技术
... <stdio.h>
int main()
{
struct stat s1;
int status = stat(<const char* denoting pathname>, &s1);
printf(“Path is a directory : %d\n”, S_ISDIR(s1.st_mode));
return 0;
}
对于 I/O 操作较多的程序，这样的不一致就意味着需要进行大量的工程工作才能...
“:” (colon) in C struct - what does it mean? [duplicate]
... struct
{
short a : 4;
short b : 3;
} test2;
struct
{
char a : 4;
char b : 3;
} test3;
struct
{
char a : 4;
short b : 3;
} test4;
printf("test1: %d\ntest2: %d\ntest3: %d\ntest4: %d\n", sizeof(test1), sizeof(test2), sizeof(test3), sizeof(test4));
test...
What is a segmentation fault?
...hen you try to write to a portion of memory that was marked as read-only:
char *str = "Foo"; // Compiler marks the constant string as read-only
*str = 'b'; // Which means this is illegal and results in a segfault
Dangling pointer points to a thing that does not exist any more, like here:
char *p...
What is move semantics?
...:
#include <cstring>
#include <algorithm>
class string
{
char* data;
public:
string(const char* p)
{
size_t size = std::strlen(p) + 1;
data = new char[size];
std::memcpy(data, p, size);
}
Since we chose to manage the memory ourselves, we need...
Is gcc's __attribute__((packed)) / #pragma pack unsafe?
....h>
#include <stddef.h>
int main(void)
{
struct foo {
char c;
int x;
} __attribute__((packed));
struct foo arr[2] = { { 'a', 10 }, {'b', 20 } };
int *p0 = &arr[0].x;
int *p1 = &arr[1].x;
printf("sizeof(struct foo) = %d\n", (int)sizeof(str...
How do I trim whitespace from a string?
... Hello ")
' Hello'
Also, note that str.strip() removes other whitespace characters as well (e.g. tabs and newlines). To remove only spaces, you can specify the character to remove as an argument to strip, i.e.:
>>> " Hello\n".strip(" ")
'Hello\n'
...
“sending 'const NSString *' to parameter of type 'NSString *' discards qualifiers” warning
...he term on its right only if there's nothing on its left side (e. g. const char * and a char const * are non-const pointers to const char, but char *const is a const pointer to non-const char).
– user529758
Oct 11 '12 at 4:29
...
Why is “while ( !feof (file) )” always wrong?
...e is again std::cin, just as before.
POSIX, write(2) to flush a buffer:
char const * p = buf;
ssize_t n = bufsize;
for (ssize_t k = bufsize; (k = write(fd, p, n)) > 0; p += k, n -= k) {}
if (n != 0) { /* error, failed to write complete buffer */ }
The result we use here is k, the numb...
Why historically do people use 255 not 256 for database field magnitudes?
You often see database fields set to have a magnitude of 255 characters, what is the traditional / historic reason why? I assume it's something to do with paging / memory limits, and performance but the distinction between 255 and 256 has always confused me.
...