gdb/ddd Program received signal SIGILL

Question

I wrote a very simple program in Linux using c++, which downloads images from some website over http (basically developed a http client request), using cURL libraries. http://curl.haxx.se/libcurl/c/allfuncs.html

#define CURL_STATICLIB
#include <stdio.h>
#include <stdlib.h>
#include </usr/include/curl/curl.h>
#include </usr/include/curl/stdcheaders.h>
#include </usr/include/curl/easy.h>

size_t write_data(void *ptr, size_t size, size_t nmemb, FILE *stream) {
    size_t written = fwrite(ptr, size, nmemb, stream);
    return written;
}

int main(void) {
    CURL *curl;
    FILE *fp;
    CURLcode res;

    char *url = "http://www.example.com/test_img.png"; 
    char outfilename[FILENAME_MAX] = "/home/c++_proj/output/web_req_img.png";
    curl = curl_easy_init();
    if (curl) {
        fp = fopen(outfilename,"wb");
        curl_easy_setopt(curl, CURLOPT_URL, url);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, write_data);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);
        res = curl_easy_perform(curl);
        /* always cleanup */
        curl_easy_cleanup(curl);
        fclose(fp);
    }
    return 0;
}

I verified the code, and it works fine. I can see the image is downloaded and that I can view the image (with no errors or warnings). Since I plan on expanding my code, I tried to install ddd, and use the debugger, but the debugger doesn't work, and my program exits with some sort of Signal errors, when I try to run my program with ddd.

This is the error:

 (Threadd debugging using libthread_db enabled)
 Using host libthread_db library "/lib/arm-linux-gnueadihf/libthread_db.so.1"

 Program received signal SIGILL, illegal instruction.
 0xb6a5c4C0 in ?? () from /usr/lib/arm-linux-gnueadbihf/libcrypto.so.1.0.0

First I thought that I didn't properly install ddd, so I went back to gdb, but I get the exact same errors, when I run the program. (And I believe that I am using the latest version of gdb and ddd)

Then I tried to use ddd on another simple program, that doesn't involve cURL library, and it worked fine !!!

Does anyone know why this is the case, and what is the solution? Do I somehow need to point to cURL libraries while ddd is running? But, in the past, I don't recall doing this with different set of libraries! Maybe it is something abuot the cURL that ddd doesn't like? But the program runs fine itself without the debugger! I would appreciate some help.

Answer 1

I am guessing it may be part of some instruction set detection code. Just let the program continue and see if it handles the signal by itself (since it runs outside of gdb, it probably does). Alternatively, you can tell gdb to not bother you with SIGILL at all before you run the program: handle SIGILL pass nostop noprint.

It's only a problem if the program dies, which was not clear from your question.