coredump时的调用栈: #0 0x081eff2c in addbyter () #1 0x081f05b8 in dprintf_formatf () #2 0x081f15cf in curl_mvsnprintf () #3 0x081f0079 in curl_msnprintf () #4 0x081ef55c in Curl_failf () #5 0x081fa1a3 in Curl_resolv_timeout () #6 0xeb8fbdd4 in ?? () #7 0x00000000 in ?? () coredump的原因是因为curl的DNS解析超时控制是使用SIGALARM实现的。 这样导致发现SIGALARM会出现多线程修改同一个全局变量,由此产生了COREDUMP。 问题发生的前提是设置了CURLOPT_TIMEOUT或CURLOPT_CONNECTTIMEOUT,并且值不为0。 解决办法: 1) 设置CURLOPT_NOSIGNAL的值为1 2) 使用c-ares(configure时指定参数--enable-ares) lib/curl_setup.h(异步模式使用c-ares控制DNS解析超时): 只有当configure时指定了--enable-ares才会定义USE_ARES。 #ifdef USE_ARES # define CURLRES_ASYNCH # define CURLRES_ARES /* now undef the stock libc functions just to avoid them being used */ # undef HAVE_GETADDRINFO # undef HAVE_GETHOSTBYNAME #elif defined(USE_THREADS_POSIX) || defined(USE_THREADS_WIN32) # define CURLRES_ASYNCH # define CURLRES_THREADED #else # define CURLRES_SYNCH #endif lib/hostip.c(同步模式使用ALARM控制DNS解析超时): 只有定义了CURLRES_SYNCH,才可能定义USE_ALARM_TIMEOUT。 #if defined(CURLRES_SYNCH) && \ defined(HAVE_ALARM) && defined(SIGALRM) && defined(HAVE_SIGSETJMP) /* alarm-based timeouts can only be used with all the dependencies satisfied */ #define USE_ALARM_TIMEOUT #endif 相关源代码: lib/asyn-ares.c: Curl_resolver_getaddrinfo lib/hostasyn.c(基于c-ares的异步版本Curl_getaddrinfo): Curl_resolver_getaddrinfo <-- Curl_getaddrinfo 从缓存中找(hostip.c): fetch_addr <-- Curl_resolv hostip.c: Curl_ipv4_resolve_r <-- Curl_getaddrinfo <-- Curl_resolv hostip.c: curl_jmpenv <-- sigaction(SIGALRM, alarmfunc)/sigsetjmp(curl_jmpenv) <- Curl_resolv_timeout <- url.c: Curl_resolv_timeout(hostname) <-- resolve_server <-- create_conn <-- Curl_connect multi.c: Curl_connect <-- transfer.c Curl_connect <-- Curl_reconnect_request url.c: Curl_reconnect_request <-- Curl_do multi.c: Curl_do <-- multi_runsingle <-- curl_multi_perform <-- multi_socket <-- curl_multi_socket