Segfault in shared object when writeln

[ed via Digitalmars-d-learn]

On Wednesday, 4 June 2014 at 03:49:25 UTC, Harpo wrote:
> Hello I am having the following problem. I am trying to turn a 
> program I have written into a shared object. I have ran into 
> some problems however. When I use writeln instead of printf my 
> program segfaults. I have edited the code to just the parts 
> causing the problem.
>
> =================main.d the so========================
>
> import std.stdio;
> import core.stdc.stdio;
>
> extern (C) void main(){
>  	writeln("Does it work?");
> 	printf("Works");
> }
>
> ==============main.c the main executable======================
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <dlfcn.h>
>
> int main() {
>   printf("+main()\n");
>
>   void *lh = dlopen("THE PATH EDITED FOR MY SECURITY", 
> RTLD_LAZY);
>   if (!lh) {
>     fprintf(stderr, "dlopen error: %s\n", dlerror());
>     exit(1);
>   }
>   printf("libdll.so is loaded\n");
>
>   void (*fn)() = dlsym(lh, "main");
>   char *error = dlerror();
>   if (error) {
>     fprintf(stderr, "dlsym error: %s\n", error);
>     exit(1);
>   }
>   printf("dll() function is found\n");
>   (*fn)();
>
>   printf("unloading libdll.so\n");
>   dlclose(lh);
>
>   printf("-main()\n");
>   return 0;
> }
>
> ========================The compile script===============
>
> dmd -c main.d -fPIC
>
> dmd -oflibdll.so main.o -shared -defaultlib=libphobos2.so 
> -L-rpath=/usr/lib/x86_64-linux-gnu -L-ldl -gc
>
> gcc -c main.c
> gcc -rdynamic main.o -o main -ldl
>
> =====================================================================
> When I have just printf is works. When I have writeln it 
> segfaults.
>
> This fails
>
> import std.stdio;
>
> extern (C) void main(){
>  	writeln("Does it work?");
> }
>
> This works
>
> import core.stdc.stdio;
>
> extern (C) void main(){
> 	printf("Works");
> }
>
> ===========================================================================
>
> Any one know whats up? Thanks!
> -Harpo

I believe you need to initialise the D runtime in your D code 
before using Phobos or druntime itself in this manner. The printf 
call just wraps the C runtime but writeln requires the D runtime 
to be initialised.

Check out
http://dlang.org/phobos/core_runtime.html#.Runtime.initialize
http://dlang.org/phobos/core_runtime.html#.Runtime.terminate

Cheers,
ed



Cheers,
ed