在我的MAC OS上,atomic<T*>是免费的.
#include <iostream>
#include <atomic>
int main() {
std::cout << std::atomic<void*>().is_lock_free() << std::endl;
return 0;
}
output: 1
我想知道是否atomic<T*>总是免费锁定？
有参考介绍吗？
当我使用 dig
$ dig www.google.com
; <<>> DiG 9.10.6 <<>> www.google.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59489
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 4, ADDITIONAL: 9
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;www.google.com. IN A
;; ANSWER SECTION:
www.google.com. 23 IN A 69.171.247.71
;; AUTHORITY SECTION:
google.com. 124333 IN NS ns4.GOoGLE.cOM.
google.com. 124333 IN NS ns1.GOoGLE.cOM.
google.com. 124333 IN NS …我列入<error.h>.
#include <error.h>
#include <unistd.h>
ssize_t rio_readn(int fd, void *buf, size_t n)
{
size_t nleft = n;
char *rbuf = buf;
while(nleft > 0)
{
int nread = read(fd, rbuf, nleft);
if(nread < 0)
{
if(error == EINTR)
nread = 0;
else
return -1;
}
else if(nread == 0)
break;
nleft -= nread;
rbuf += nread;
}
return n - nleft;
}