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digitalmars.D.learn - SEGFAULT when converting C string to string

reply 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.
Mar 18
parent reply "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
Mar 18
parent 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!
Mar 18