Seg fault when calling C code

[Ali Çehreli via Digitalmars-d-learn]

On 05/16/2014 08:15 AM, Andrew Brown wrote:

 > I guess my confusion came about because in the page about interfacing
 > with C, there's a static array example where parameters are given in
 > terms D understands:
 >
 > extern (C)
 > {
 >    void foo(ref int[3] a); // D prototype
 > }
 >
 > I guess D has no problem translating that into a simple pointer that C
 > can deal with. I assumed the same would be true of dynamic arrays, but
 > maybe the leap is too far?

There is a major difference. A static array is direct equivalent of C 
arrays when it comes to how they are stored in memory. Static arrays are 
simply consecutive elements. (Of course, static arrays are superior to C 
arrays in many other aspects. :))

One difference between C arrays is the fact that static arrays are 
by-value when passed even to functions. (No more "decaying to pointer to 
first element" confusion.)

Since we know that references are implemented as pointers, 'ref int[3] 
a' is passed as a.ptr. Since the memory layout is the same as a C array, 
it works perfectly.

On the other hand, dynamic arrays (aka slices) are the equivalent of the 
following struct:

struct Slice(T)
{
     size_t length;
     T * ptr;    // points to an array of elements
}

Ali