Given the following code:
#include <gtk/gtk.h>
int main(int argc, char *argv[])
{
gtk_init(&argc, &argv);
GdkDisplay *display = gdk_display_open(":2");
gtk_main();
return(0);
}
How can you catch the error, when the X server for display :2 is no longer running?
The exact error is:
Fatal IO error 11 (Resource temporarily unavailable) on X server :2.
Related
using Linux (ubuntu 20.04) machine, openssl 3.0.7 is installed , running a sample code for signing.
we followed below procedure for signing. getting segmentation fault in EVP_DigestFinal_ex.
segmentation fault is happening due to mdctx->algctx=0x0. while debugging the code mdctx->algctx is updated in EVP_DigestInit_ex but latter it was freed in EVP_DigestSignInit. not sure what we are missing and how to update mdctx->algctx to avoid the crash.
#include <stdio.h>
#include <string.h>
#include <openssl/evp.h>
#include <openssl/provider.h>
EVP_PKEY *pkey = NULL;
generate_key(){
EVP_PKEY_CTX *ctx=NULL;
pkey=EVP_PKEY_new();
ctx=EVP_PKEY_CTX_new(pkey,NULL);
ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL);
if (!ctx)
printf(" key gen failed");
if (EVP_PKEY_keygen_init(ctx) <= 0)
printf(" key gen failed");
if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 512) <= 0)
printf(" key gen failed");
/* Generate key */
if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
printf(" key gen failed");
}
int main(int argc, char *argv[])
{
EVP_MD_CTX *mdctx;
const EVP_MD *m_md;
const EVP_MD *md;
EVP_PKEY *m_key;
EVP_PKEY *ed_pkey = NULL;
EVP_PKEY_CTX *ed_pctx = NULL;
// OSSL_PROVIDER *default;
size_t sign_len = 0;
u_int8_t m_sign_buf[2048];
int ret = 0;
char mess1[] = "Test Message\n";
char mess2[] = "Hello World\n";
unsigned char *outdigest = NULL;
unsigned int md_len = 0, i;
printf("args : %s\n",argv[1]);
//default = OSSL_PROVIDE_load(NULL, "default");
//md = EVP_get_digestbyname("SHA256");
//md = EVP_sha256();
md = EVP_MD_fetch(NULL, "SHA256", NULL); //;
if (md == NULL) {
printf("Unknown message digest %s\n", argv[1]);
exit(1);
}
generate_key();
printf("value of md %s\n",md);
mdctx = EVP_MD_CTX_new();
if((EVP_DigestInit_ex(mdctx, md, NULL)) != 1)
printf("EVP_DigestInit_ex failed \n");
if((EVP_DigestSignInit(mdctx, NULL, md, NULL, pkey)) != 1)
printf("EVP_DigestSignInit failed \n");
if((EVP_DigestSignUpdate(mdctx, mess1, strlen(mess1))) != 1)
printf("EVP_DigestSignUpdate failed \n");
//EVP_DigestUpdate(mdctx, mess2, strlen(mess2));
if((EVP_DigestSignFinal(mdctx, (u_int8_t*)NULL, &sign_len)) != 1)
printf("EVP_DigestSignFinal failed \n");
if((EVP_DigestSignFinal(mdctx, m_sign_buf, &sign_len)) != 1)
printf("EVP_DigestSignFinal 2 failed \n");
/* Allocate the output buffer */
outdigest = OPENSSL_malloc(EVP_MD_get_size(md));
if (outdigest == NULL)
printf("outdigest failed \n");
if((EVP_DigestFinal_ex(mdctx, outdigest, &md_len)) != 1)
printf("EVP_DigestFinal_ex failed \n");
EVP_MD_CTX_free(mdctx);
/* Print out the digest result */
BIO_dump_fp(stdout, outdigest, &md_len);
exit(0);
}
`
```
Thanks,
while debugging the code mdctx->algctx is updated in EVP_DigestInit_ex but latter it was freed in EVP_DigestSignInit. not sure what we are missing and how to update mdctx->algctx to avoid the crash.
CRASH Info:
Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7d99422 in SHA256_Final (md=0x5555555a88d0 "\250UUU\005", c=0x0)
at ../openssl-3.0.7/include/crypto/md32_common.h:194
194 size_t n = c->num;
(gdb) bt
#0 0x00007ffff7d99422 in SHA256_Final (md=0x5555555a88d0 "\250UUU\005", c=0x0)
at ../openssl-3.0.7/include/crypto/md32_common.h:194
#1 0x00007ffff7e2628c in sha256_internal_final (ctx=0x0, out=0x5555555a88d0 "\250UUU\005", outl=0x7fffffffda98,
outsz=32) at ../openssl-3.0.7/providers/implementations/digests/sha2_prov.c:72
#2 0x00007ffff7cbadf6 in EVP_DigestFinal_ex (ctx=0x555555580d80, md=0x5555555a88d0 "\250UUU\005",
isize=0x7fffffffdad8) at ../openssl-3.0.7/crypto/evp/digest.c:446
#3 0x000055555555575f in main (argc=1, argv=0x7fffffffe458) at test2.c:90
I have a program compiled and running on Ubuntu server 16.04, in C using Mongo C driver. This works without a problem. If I move this executable to a new installation, I get an error when executing;
testuser#usrv1604:~/bin$ ./error-example
./error-example: symbol lookup error: ./error-example: undefined symbol: mongoc_uri_new_with_error
Always the same error message.
Please see simplified code example below:
#include <stdio.h>
#include <strings.h>
#include <mongoc.h>
int
main (int argc, char *argv[])
{
const char *uri_string = "mongodb://localhost:27017";
mongoc_uri_t *uri;
mongoc_client_t *client;
mongoc_database_t *database;
mongoc_collection_t *collection;
bson_t *command, reply, *insert;
bson_t *b;
bson_error_t error;
mongoc_init ();
uri = mongoc_uri_new_with_error (uri_string, &error);
if (!uri) {
fprintf (stderr,
"failed to parse URI: %s\n"
"error message: %s\n",
uri_string,
error.message);
return EXIT_FAILURE;
}
client = mongoc_client_new_from_uri (uri);
if (!client) {
fprintf(stderr, "mongoc_client_new_from_uri() failed \n");
return EXIT_FAILURE;
}
mongoc_client_set_appname (client, "log-lme");
database = mongoc_client_get_database (client, "sds");
collection = mongoc_client_get_collection (client, "sds", "test");
//
// update db
//
// clean up
mongoc_collection_destroy (collection);
mongoc_database_destroy (database);
mongoc_uri_destroy (uri);
mongoc_client_destroy (client);
mongoc_cleanup ();
return EXIT_SUCCESS;
}
Please check the mongoc driver version installed on the target system. You must have version 1.8 or later to use this API: http://mongoc.org/libmongoc/1.8.0/mongoc_uri_new_with_error.html
I am implementing a simple multithreaded FTP client server where I am facing a problem which is strange for me( as I am no master in C++ and threads).
The code I have written works normally until I #include <thread>.
Once I include the thread class the program fails on listen and gives a 10022 error. (I haven't done anything related to threads yet, only import).
Below is the code. The method is called from main().
#include <winsock2.h>
#include <ws2tcpip.h>
#include <process.h>
#include <winsock.h>
#include <iostream>
#include <windows.h>
#include <fstream>
#include <string>
#include <stdio.h>
#include <time.h>
#include <thread>
using namespace std;
void initializeSockets()
{
try{
logEvents("SERVER", "Initializing the server");
WSADATA wsadata;
if (WSAStartup(0x0202,&wsadata)!=0){
cout<<"Error in starting WSAStartup()\n";
logEvents("SERVER", "Error in starting WSAStartup()");
}else{
logEvents("SERVER", "WSAStartup was suuccessful");
}
gethostname(localhost,20);
cout<<"hostname: "<<localhost<< endl;
if((hp=gethostbyname(localhost)) == NULL) {
cout << "gethostbyname() cannot get local host info?"
<< WSAGetLastError() << endl;
logEvents("SERVER", "Cannot get local host info. Exiting....");
exit(1);
}
//Create the server socket
if((serverSocket = socket(AF_INET,SOCK_STREAM,0))==INVALID_SOCKET)
throw "can't initialize socket";
//Fill-in Server Port and Address info.
serverSocketAddr.sin_family = AF_INET;
serverSocketAddr.sin_port = htons(port);
serverSocketAddr.sin_addr.s_addr = htonl(INADDR_ANY);
//Bind the server port
if (bind(serverSocket,(LPSOCKADDR)&serverSocketAddr,sizeof(serverSocketAddr)) == SOCKET_ERROR)
throw "can't bind the socket";
cout << "Bind was successful" << endl;
logEvents("SERVER", "Socket bound successfully.");
if(listen(serverSocket,10) == SOCKET_ERROR)
throw "couldn't set up listen on socket";
else
cout << "Listen was successful" << endl;
logEvents("SERVER", "Socket now listening...");
//Connection request accepted.
acceptUserConnections();
}
catch(char* desc)
{
cerr<<str<<WSAGetLastError()<<endl;
logEvents("SERVER", desc);
}
logEvents("SERVER", "Closing client socket...");
closesocket(clientSocket);
logEvents("SERVER", "Closed. \n Closing server socket...");
closesocket(serverSocket);
logEvents("SERVER", "Closed. Performing cleanup...");
WSACleanup();
}
int main(void){
initializeSockets();
return 0;
}
I have read the thread Winsock Error 10022 on Listen but I don't think that this has solution to my problem.
Error 10022 is WSAEINVAL. The documentation for listen() clearly states:
WSAEINVAL
The socket has not been bound with bind.
The reason your code stops working when you add #include <thread> is because your call to bind() is being altered to no longer call WinSock's bind() function, but to instead call the STL's std::bind() function. Your using namespace std statement is masking that issue (this is one of many reasons why using namespace std is such a bad practice - teach yourself to stop using that!).
So you need to either:
get rid of using namespace std.
qualify bind() with the global namespace so it calls WinSock's function:
if (::bind(...) == SOCKET_ERROR)
I have used the below code to use as an example to consume the REST services in VC++. I am getting an error stating "A Connection with the Server Could Not be Established". IIs version of my system is IIS 6.0. Please let me know what could be the problem. Thanks in advance.
#include "stdafx.h"
#include "http_client.h"
#include "filestream.h"
#include "iostream"
#include "sstream"
#include "conio.h"
#include "Windows.h"
using namespace utility;
using namespace web;
using namespace web::http;
using namespace web::http::client;
using namespace concurrency::streams;
int _tmain(int argc, _TCHAR* argv[])
{
auto fileStream = std::make_shared<ostream>();
// Open stream to output file.
pplx::task<void> requestTask = fstream::open_ostream(U("results.html")).then([=](ostream outFile)
{
*fileStream = outFile;
// Create http_client to send the request.
http_client client(U("http://www.bing.com/"));
uri_builder builder(U("/search"));
builder.append_query(U("q"), U("Casablanca CodePlex"));
return client.request(methods::GET, builder.to_string());
// Build request URI and start the request.
})
// Handle response headers arriving.
.then([=](http_response response)
{
printf("Received response status code:%u\n", response.status_code());
// Write response body into the file.
return response.body().read_to_end(fileStream->streambuf());
})
// Close the file stream.
.then([=](size_t)
{
return fileStream->close();
});
// Wait for all the outstanding I/O to complete and handle any exceptions
try
{
requestTask.wait();
}
catch (const std::exception &e)
{
printf("Error exception:%s\n", e.what());
}
Sleep(5000);
return 0;
}
The following works without error on OSX 10.6, but fails in the iphone simulator using SDK 4.1
#include <arpa/inet.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/tcp.h>
#include <sys/un.h>
#include <string.h>
int main(void) {
int sock = socket(AF_UNIX, SOCK_DGRAM, 0);
struct sockaddr_un sock_addr;
memset(&sock_addr, 0, sizeof(struct sockaddr_un));
sock_addr.sun_family = AF_UNIX;
strcpy(sock_addr.sun_path, "/tmp/sock");
int err = bind(sock, (struct sockaddr*)&sock_addr, sizeof(struct sockaddr_un));
if(err == -1) {
perror("bind: ");
}
}
Error is "Address family not supported by protocol family"
Any ideas?
You really need to check sock already - most likely, the socket creation is what failed already.
My guess is that AF_UNIX/SOCK_DGRAM is not supported; try SOCK_STREAM instead.