• DFTW (49/49) Mar 18 2019 I'm writing a shared library in C to be used from a C program, so
• H. S. Teoh (10/27) Mar 18 2019 [...]
• DFTW (4/16) Mar 18 2019 That's right. From the small code samples I've seen, they had no

DFTW <jckj33 gmail.com> writes:

I'm writing a shared library in C to be used from a C program, so 
I went to my small tests. That one failed give a SEGFAULT on the 
std.conv.to call.

This is the pice of D code/the library:

extern(C) int foo(const char *name, int age)
{
     import core.stdc.stdio : printf;
     import core.stdc.stdlib;
     import std.conv : to;
     printf("printf() got called! age = %d\n", age);
     printf("name = [%s]\n", name);
     //auto nm = to!string(name); // <-- everything works until I 
uncomment this line.
     return age * 2;
}

if matters, compiled with dub: "targetType" : "dynamicLibrary"
on 64-bit machine.

This is the piece of C code, foo.c:

#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>

int main(void)
{
   printf("+main();\n");
   const char* libpath = "mylib.so";
   void *lh = dlopen(libpath, RTLD_LAZY);
   if(!lh) {
     fprintf(stderr, "dlopen error: %s\n", dlerror());
     return EXIT_FAILURE;
   }

   int (*fn)(const char*, int) = dlsym(lh, "foo");
   char *err = dlerror();
   if(err) {
     fprintf(stderr, "dlsym error: %s\n", err);
     return EXIT_FAILURE;
   }
   const char *name = "jhon";
   int age = 18;
   int result = (*fn)(name, age);
   printf("unloading lib");
   dlclose(lh);
   printf("result = %d\n", result);
   printf("-main()\n");
   return 0;
}

compile as:

gcc foo.c -ldl

My OS is Ubuntu version 18

I'm assuming const char* both in C and D are raw pointers.

"H. S. Teoh" <hsteoh quickfur.ath.cx> writes:

On Mon, Mar 18, 2019 at 10:20:35PM +0000, DFTW via Digitalmars-d-learn wrote:
 I'm writing a shared library in C to be used from a C program, so I
 went to my small tests. That one failed give a SEGFAULT on the
 std.conv.to call.
 
 This is the pice of D code/the library:
 
 extern(C) int foo(const char *name, int age)
 {
     import core.stdc.stdio : printf;
     import core.stdc.stdlib;
     import std.conv : to;
     printf("printf() got called! age = %d\n", age);
     printf("name = [%s]\n", name);
     //auto nm = to!string(name); // <-- everything works until I uncomment
 this line.
     return age * 2;
 }

[...]

Most likely explanation: you failed to call rt_init() before using a
language feature that requires druntime to be initialized. In this case,
a GC allocation by std.conv.to!string.

Call rt_init() immediately after loading the library, and calling
rt_term() after you're done with it, should fix this problem.


T

-- 
Talk is cheap. Whining is actually free. -- Lars Wirzenius

DFTW <jckj33 gmail.com> writes:

On Monday, 18 March 2019 at 22:33:21 UTC, H. S. Teoh wrote:
 On Mon, Mar 18, 2019 at 10:20:35PM +0000, DFTW via 
 Digitalmars-d-learn wrote:
 [...]

 [...]

 Most likely explanation: you failed to call rt_init() before 
 using a language feature that requires druntime to be 
 initialized. In this case, a GC allocation by 
 std.conv.to!string.

 Call rt_init() immediately after loading the library, and 
 calling
 rt_term() after you're done with it, should fix this problem.


 T

That's right. From the small code samples I've seen, they had no 
rt_init() usage, so I wasn't aware I've had to call it.
Thanks!