I have used cURL in my app. It works fine (no errors) in debug mode. However, if i switch code to Release build, app start crashing. I am using VC 2013
My code:
data_downloads.curl = curl_easy_init();
data_downloads.curlData = (CURL_DOWNLOADED_DATA *)malloc(sizeof(CURL_DOWNLOADED_DATA));
data_downloads.curlData->data = (char *)malloc(sizeof(char));
data_downloads.curlData->data[0] = '\0';
curl_easy_setopt(data_downloads.curl, CURLOPT_WRITEFUNCTION, &my_curl_writeCallback);
curl_easy_setopt(data_downloads.curl, CURLOPT_WRITEDATA, data_downloads->curlData);
curl_easy_setopt(data_downloads.curl, CURLOPT_VERBOSE, 1L); //tell curl to output its progress
curl_easy_setopt(data_downloads.curl, CURLOPT_URL, USER_INFO_URL);
curl_easy_setopt(data_downloads.curl, CURLOPT_COOKIEFILE, "cookie.txt");
curl_easy_perform(data_downloads.curl); //-- it crashes here
I noticed that in debug mode, VC adds some space to the stack at every of your functions. Would a function briefly be out of bounds and overwrite a few bytes of the stack, then this will not be noticed...until you compile for release.
You should further check that all libraries for the release mode are the proper ones. VC knows many library types for many models (for DLLs, multi-threaded/not, ...). Check them against the libraries for your debugging mode.
These are the issues I came across. There may be other issues.
Related
I saw some c codes relative to the topic. I've tried them but only I get errors saying a heap of errors of curl.h. I googled much but couldn't find a good answer. I'm using CCS C compiler version v5.008. I really want to solve this problem soon.
I tried to compile the code from the following link.
enter link description here
#include <stdio.h>
#include <curl/curl.h>
int main(void)
{
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
/* example.com is redirected, so we tell libcurl to follow redirection */
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);
/* Perform the request, res will get the return code */
res = curl_easy_perform(curl);
/* Check for errors */
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
/* always cleanup */
curl_easy_cleanup(curl);
}
return 0;
}
Gives me error: "Error 119"C:\Users\Sisitha\Documents\CCS C Projects\ Testing\curl\curlbuild.h" Line 556(145,183): " Unknown non-configure build target" "
I'm on Windows 7(64bit)
Please help me to solve this matter.
Thanks!
curl uses GNU autotools to be built from source. There's a library to be built and configured, for the example program and header file, to link against. The error :
Error 119"C:\Users\Sisitha\Documents\CCS C Projects\ Testing\curl\curlbuild.h" Line 556(145,183): " Unknown non-configure build target"
Suggests that the curl.h you included, hasn't been configured, by the standard GNU ./configure; make; make install build sequence.
Curl installation instructions Install -- how to install curl
I'm developing a system that tracks objects with a P(an)T(ilt)Z(oom) camera which can be controlled via HTTP requests. The C application I develop is supposed to receive position data of the tracked object and to send commands to the camera to control the pan and tilt angle. In addition to these commands the camera has to receive a session refresh command every 5 seconds. HTTP Digest Authorization has to be used for the connection.
I'm sending the HTTP request with libcurl. I figured already out that for digest auth one needs to use on and the same curl handle for all requests in this stackoverflow post.
For sending the session refresh command periodically I tried to use a thread which is just doing this:
while(1)
{
usleep(5000000);
sessionContinue(g_Config.cam_ip);
}
With sessionContinue looking like this:
CURLcode sessionContinue(char* url)
{
CURLcode res;
char requestURL[40];
char referer[47];
struct curl_slist *headers=NULL;
strcpy(requestURL , url);
strcat(requestURL, CAM_SESSION_CONTINUE);
strcpy(referer , "Referer: http://");
strcat(referer , url);
strcat(referer , CAM_MONITOR);
headers = curl_slist_append(headers,"Connection:keep-alive");
headers = curl_slist_append(headers, camCookie);
// In windows, this will init the winsock stuff
curl_global_init(CURL_GLOBAL_ALL);
curl_easy_reset(curl);
if(curl)
{
// First set the URL that is about to receive our POST. This URL can
//just as well be a https:// URL if that is what should receive the
//data.
curl_easy_setopt( curl , CURLOPT_URL , requestURL );
curl_easy_setopt( curl , CURLOPT_HTTPHEADER , headers );
curl_easy_setopt( curl , CURLOPT_HTTPGET , 1 );
curl_easy_setopt( curl , CURLOPT_USERNAME , "root" );
curl_easy_setopt( curl , CURLOPT_PASSWORD , "password" );
curl_easy_setopt( curl , CURLOPT_HTTPAUTH , CURLAUTH_BASIC | CURLAUTH_DIGEST );
// Perform the request, res will get the return code
res = curl_easy_perform(curl);
// Check for errors
if(res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed # %s:%d : %s\n", curl_easy_strerror(res) , __FILE__ , __LINE__ );
}
return res;
}
The application always crashed with segmentation fault after executing curl_easy_perform(curl). So I read the libcurl tutorial again and now I know that using one curl handle in multiple threads is a no go.
What I tried then was to use a timer with SIGALRM to implement the periodic session refresh. This didn't change the problem with the crash at curl_easy_perform(curl). The strange thing is that the application doesn't crash when sending the normal command to control the pan and tilt position which uses the same curl handle. The only difference between session refresh and pan/tilt command is that session refresh uses GET and pan/tilt uses POST.
Are there any other possibilities to send pan/tilt commands continuously with a short pause every 5 seconds used to send the session refresh?
You have a long range of problems in one small program. Here's a few:
You might overflow one of those small fixed-size buffers with the dangerous unbounded C functions you use. Quite likely one of them is the reason for the segfault.
curl_global_init() is documented to be called once, you call it over and over again - this even without calling curl_global_cleanup() in between. You obviously call curl_easy_init() somewhere out of the function and you should move the global init there.
'referer' gets filled with data but is never used otherwise
Another advice is to use CURLOPT_ERRORBUFFER to get error messages in rather than curl_easy_strerror() as you may get some extra details then. And of course to set CURLOPT_VERBOSE while debugging the request to see that things look the way you want it.
Thanks for your comment Daniel Stenberg. I'm now calling curl_global_init() just once when the handle has been set up. referer wasn't really needed here, but I had forgotten to remove it before pasting the code here.
The reason for the segmentation fault was that the session refresh command and the commands for pan and tilt tried to use one and the same curl handle at the same time, which obviously can't really work. So the solution with the timer and SIGALRM wasn't the problem. The segmentation faults have been solved by adding a mutex lock to avoid concurrent accesses to the curl handle.
Hello what I am trying to do is send post method twice, however when I send it a second time the information from the first time is also being included and I do not want that.
To illustrate what I mean, this is the code that sends using post method. (the handle curl was already created)
void process(char* transferBuffer) {
curl_easy_setopt(curl, CURLOPT_URL, "http://localhost/cpp.php");
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, transferBuffer);
res = curl_easy_perform(curl);
if (res != CURLE_OK)
fprintf(stderr, "curl_easy_perform() failed: %s\n",
curl_easy_strerror(res));
}
If I do something like:
process("name=John"); - webserver receives name=John
process("name=El"); - webserver receives name=John AND name=El
What I want to do is somehow clean previously used data;
the curl handle was already created ... What I want to do is somehow clean previously used data
All I can say is that if you want to reuse your curl handle - which is a best practice, you should reset it with curl_easy_reset before re-setting your options and re-performing the transfer.
Note that without the complete sample code (including the creation of your curl handle, etc) it is quite hard to provide a detailed answer.
This is my very first C program and I'm using this example libcurl code from their website:
#include <stdio.h>
#include <curl/curl.h>
int main(void)
{
CURL *curl;
CURLcode res;
curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "https://google.com/");
#ifdef SKIP_PEER_VERIFICATION
/*
* If you want to connect to a site who isn't using a certificate that is
* signed by one of the certs in the CA bundle you have, you can skip the
* verification of the server's certificate. This makes the connection
* A LOT LESS SECURE.
*
* If you have a CA cert for the server stored someplace else than in the
* default bundle, then the CURLOPT_CAPATH option might come handy for
* you.
*/
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 0L);
#endif
#ifdef SKIP_HOSTNAME_VERFICATION
/*
* If the site you're connecting to uses a different host name that what
* they have mentioned in their server certificate's commonName (or
* subjectAltName) fields, libcurl will refuse to connect. You can skip
* this check, but this will make the connection less secure.
*/
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 0L);
#endif
res = curl_easy_perform(curl);
/* always cleanup */
curl_easy_cleanup(curl);
}
return 0;
}
So in xcode I created a "group" called it curl and added all the files in the curl directory:
And now I'm getting these Build errors:
What am I doing wrong? Any advice would help, thanks!
Mac OS X comes with a copy of libcurl, so your application doesn't need its own copy.
You didn't mention the version of Xcode you're using. The following applies to 3.2, but may not work in 4.
To use the version of libcurl provided by the system, go to Project, then Add To Project. In the dialog that comes up, type /usr/lib and press enter. Find libcurl.dylib in the list of files and click Add.
For Xcode 4.5:
Click on the project in the left pane.
Click on the target.
Go to the "Build Phases" section.
Under "Link Binary with Libraries", click the plus sign.
From there you should be able to search for "libcurl.dylib".
Now when you build it should be able to link to the library.
For XCode 7, just right click on the project or group you want to put the lib in, then select Add Files to "Project Name"..., and finally find the libcurl.dylib in /usr/lib directory.
So I've got a bunch of worker threads doing simple curl class, each worker thread has his own curl easy handle. They are doing only HEAD lookups on random web sites. Also locking functions are present to enable multi threaded SSL as documented here. Everything is working except on 2 web pages ilsole24ore.com ( seen in example down ), and ninemsn.com.au/ , they sometimes produce seg fault as shown in trace output shown here
#0 *__GI___libc_res_nquery (statp=0xb4d12df4, name=0x849e9bd "ilsole24ore.com", class=1, type=1, answer=0xb4d0ca10 "", anslen=1024, answerp=0xb4d0d234,
answerp2=0x0, nanswerp2=0x0, resplen2=0x0) at res_query.c:182
#1 0x00434e8b in __libc_res_nquerydomain (statp=0xb4d12df4, name=0xb4d0ca10 "", domain=0x0, class=1, type=1, answer=0xb4d0ca10 "", anslen=1024,
answerp=0xb4d0d234, answerp2=0x0, nanswerp2=0x0, resplen2=0x0) at res_query.c:576
#2 0x004352b5 in *__GI___libc_res_nsearch (statp=0xb4d12df4, name=0x849e9bd "ilsole24ore.com", class=1, type=1, answer=0xb4d0ca10 "", anslen=1024,
answerp=0xb4d0d234, answerp2=0x0, nanswerp2=0x0, resplen2=0x0) at res_query.c:377
#3 0x009c0bd6 in *__GI__nss_dns_gethostbyname3_r (name=0x849e9bd "ilsole24ore.com", af=2, result=0xb4d0d5fc, buffer=0xb4d0d300 "\177", buflen=512,
errnop=0xb4d12b30, h_errnop=0xb4d0d614, ttlp=0x0, canonp=0x0) at nss_dns/dns-host.c:197
#4 0x009c0f2b in _nss_dns_gethostbyname2_r (name=0x849e9bd "ilsole24ore.com", af=2, result=0xb4d0d5fc, buffer=0xb4d0d300 "\177", buflen=512,
errnop=0xb4d12b30, h_errnop=0xb4d0d614) at nss_dns/dns-host.c:251
#5 0x0079eacd in __gethostbyname2_r (name=0x849e9bd "ilsole24ore.com", af=2, resbuf=0xb4d0d5fc, buffer=0xb4d0d300 "\177", buflen=512, result=0xb4d0d618,
h_errnop=0xb4d0d614) at ../nss/getXXbyYY_r.c:253
#6 0x00760010 in gaih_inet (name=<value optimized out>, service=<value optimized out>, req=0xb4d0f83c, pai=0xb4d0d764, naddrs=0xb4d0d754)
at ../sysdeps/posix/getaddrinfo.c:531
#7 0x00761a65 in *__GI_getaddrinfo (name=0x849e9bd "ilsole24ore.com", service=0x0, hints=0xb4d0f83c, pai=0xb4d0f860) at ../sysdeps/posix/getaddrinfo.c:2160
#8 0x00917f9a in ?? () from /usr/lib/libkrb5support.so.0
#9 0x003b2f45 in krb5_sname_to_principal () from /usr/lib/libkrb5.so.3
#10 0x0028a278 in ?? () from /usr/lib/libgssapi_krb5.so.2
#11 0x0027eff2 in ?? () from /usr/lib/libgssapi_krb5.so.2
#12 0x0027fb00 in gss_init_sec_context () from /usr/lib/libgssapi_krb5.so.2
#13 0x00d8770e in ?? () from /usr/lib/libcurl.so.4
#14 0x00d62c27 in ?? () from /usr/lib/libcurl.so.4
#15 0x00d7e25b in ?? () from /usr/lib/libcurl.so.4
#16 0x00d7e597 in ?? () from /usr/lib/libcurl.so.4
#17 0x00d7f133 in curl_easy_perform () from /usr/lib/libcurl.so.4
My function looks something like this
int do_http_check(taskinfo *info,standardResult *data)
{
standardResultInit(data);
char errorBuffer[CURL_ERROR_SIZE];
CURL *curl;
CURLcode result;
curl = curl_easy_init();
if(curl)
{
//required options first
curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, errorBuffer);
curl_easy_setopt(curl, CURLOPT_URL, info->address.c_str());
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, writer);
curl_easy_setopt(curl, CURLOPT_WRITEDATA, &data->body);
curl_easy_setopt(curl, CURLOPT_HEADERFUNCTION, writer);
curl_easy_setopt(curl, CURLOPT_WRITEHEADER, &data->head);
curl_easy_setopt(curl, CURLOPT_DNS_USE_GLOBAL_CACHE,0);
curl_easy_setopt(curl, CURLOPT_CONNECTTIMEOUT, 30 );
curl_easy_setopt(curl, CURLOPT_NOSIGNAL,1);
curl_easy_setopt(curl, CURLOPT_NOBODY,1);
curl_easy_setopt(curl, CURLOPT_TIMEOUT ,240);
//optional options
if(info->options.follow)
{
curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1);
curl_easy_setopt(curl, CURLOPT_MAXREDIRS, info->options.redirects);
}
result = curl_easy_perform(curl);
if (result == CURLE_OK)
{
data->success = true;
curl_easy_getinfo(curl,CURLINFO_RESPONSE_CODE,&data->httpMsg);
curl_easy_getinfo(curl,CURLINFO_REDIRECT_COUNT,&data->numRedirects);
data->msg = "OK";
}
else
{
... handle error
}
return 1;
}
Now, when i call function without any threads, just calling it from main it never breaks, so I was thinking its connected to threads, or maybe how data return structure is being returned, but from what I saw in trace it looks like fault is generated in easy_perform() call, and its confusing me.
So if someone has any idea where should i look next it would be most helpful, thanks.
There is a whole section dedicated in libcurl to Multi-Threading.
The first basic rule is that you must
never share a libcurl handle (be it
easy or multi or whatever) between
multiple threads. Only use one handle
in one thread at a time.
libcurl is completely thread safe,
except for two issues: signals and
SSL/TLS handlers. Signals are used for
timing out name resolves (during DNS
lookup) - when built without c-ares
support and not on Windows.
If you are accessing HTTPS or FTPS
URLs in a multi-threaded manner, you
are then of course using the
underlying SSL library multi-threaded
and those libs might have their own
requirements on this issue. Basically,
you need to provide one or two
functions to allow it to function
properly. For all details, see this:
OpenSSL
http://www.openssl.org/docs/crypto/threads.html#DESCRIPTION
GnuTLS
http://www.gnu.org/software/gnutls/manual/html_node/Multi_002dthreaded-applications.html
NSS
is claimed to be thread-safe already
without anything required.
yassl
Required actions unknown.
When using multiple threads you should
set the CURLOPT_NOSIGNAL option to 1
for all handles. Everything will or
might work fine except that timeouts
are not honored during the DNS lookup
- which you can work around by building libcurl with c-ares support.
c-ares is a library that provides
asynchronous name resolves. On some
platforms, libcurl simply will not
function properly multi-threaded
unless this option is set.
Also, note that
CURLOPT_DNS_USE_GLOBAL_CACHE is not
thread-safe.
As mentioned in error: longjmp causes uninitialized stack frame, the latest libcurl versions (>= 7.32.0) in Debian/Ubuntu repositories contain a new multithreaded resolver to solve these problems. The c-ares support is not a good solution:
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=570436#74
"The real problem is that c-ares is not yet a full replacement for gethostby* functions (e.g. it does not support multicast DNS) and enabling it in stock libcurl packages may not be a good move (note that these are words of the upstream author of both curl and c-ares, not mine)."-