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digitalmars.D.learn - Best way to confine project to 64 bit builds only?

reply NonNull <non-null use.startmail.com> writes:
I have inherited an open source C project that assumes that the 
size of a long and the size of a pointer are the same, and I have 
translated it into very similar D just like 
https://dlang.org/blog/2018/06/11/dasbetterc-converting-make-c-to-d/

D has the size of long fixed at 64 bits, so a pointer now has to 
be 64 bits. So I want to put something into the source to ensure 
an attempt to make a 32 bit build fails. What is the best way to 
do this?
Oct 17 2020
next sibling parent reply Basile B. <b2temp gmx.com> writes:
On Saturday, 17 October 2020 at 14:50:47 UTC, NonNull wrote:

 I have inherited an open source C project that assumes that the 
 size of a long and the size of a pointer are the same, and I 
 have translated it into very similar D just like 
 https://dlang.org/blog/2018/06/11/dasbetterc-converting-make-c-to-d/

 D has the size of long fixed at 64 bits, so a pointer now has 
 to be 64 bits.


No it's wrong. A pointer always has the size of a general purpose 
register.


 So I want to put something into the source to ensure an attempt 
 to make a 32 bit build fails. What is the best way to do this?


anyway you have several options:

---
version(X86)
     static assert (false, "not for i386");
---

or

---
static assert (size_t.sizeof != 4, "blablalala");
---
Oct 17 2020
parent NonNull <non-null use.startmail.com> writes:
On Saturday, 17 October 2020 at 14:56:33 UTC, Basile B. wrote:

 On Saturday, 17 October 2020 at 14:50:47 UTC, NonNull wrote:

 I have inherited an open source C project that assumes that 
 the size of a long and the size of a pointer are the same, and 
 I have translated it into very similar D just like 
 https://dlang.org/blog/2018/06/11/dasbetterc-converting-make-c-to-d/

 D has the size of long fixed at 64 bits, so a pointer now has 
 to be 64 bits.


 No it's wrong. A pointer always has the size of a general 
 purpose register.


You misunderstand. The original C only works if the size of a 
pointer is the same as the size of a long. So when translated 
into D in a simple way where the size of a long is always 64 bits 
the D will only work if the size of a pointer is 64 bits.
Oct 17 2020
prev sibling next sibling parent reply Adam D. Ruppe <destructionator gmail.com> writes:
On Saturday, 17 October 2020 at 14:50:47 UTC, NonNull wrote:

 I have inherited an open source C project that assumes that the 
 size of a long and the size of a pointer are the same


static assert(long.sizeof == void*.sizeof);
Oct 17 2020
parent NonNull <non-null use.startmail.com> writes:
On Saturday, 17 October 2020 at 14:56:35 UTC, Adam D. Ruppe wrote:

 On Saturday, 17 October 2020 at 14:50:47 UTC, NonNull wrote:

 I have inherited an open source C project that assumes that 
 the size of a long and the size of a pointer are the same


 static assert(long.sizeof == void*.sizeof);


That's a nice clean answer!
Oct 17 2020
prev sibling parent reply Dennis <dkorpel gmail.com> writes:
On Saturday, 17 October 2020 at 14:50:47 UTC, NonNull wrote:

 I have inherited an open source C project that assumes that the 
 size of a long and the size of a pointer are the same, and I 
 have translated it into very similar D just like 
 https://dlang.org/blog/2018/06/11/dasbetterc-converting-make-c-to-d/

 D has the size of long fixed at 64 bits, so a pointer now has 
 to be 64 bits.


If you want to exactly match the original C code's semantics, I 
suggest translating (unsigned) long with c_long or c_ulong. You 
can import them here:
```
import core.stdc.config: c_long, c_ulong;
```

Then you could add this:
```
static assert(c_long.sizeof == size_t.sizeof);
```

This will fail on Windows 64 bit, where C longs are 32-bit and 
pointers 64-bit.
Oct 17 2020
parent NonNull <non-null use.startmail.com> writes:
On Saturday, 17 October 2020 at 15:03:29 UTC, Dennis wrote:

 If you want to exactly match the original C code's semantics, I 
 suggest translating (unsigned) long with c_long or c_ulong. You 
 can import them here:
 ```
 import core.stdc.config: c_long, c_ulong;
 ```

 Then you could add this:
 ```
 static assert(c_long.sizeof == size_t.sizeof);
 ```

 This will fail on Windows 64 bit, where C longs are 32-bit and 
 pointers 64-bit.


That is useful information in general, I did not know about 
core.stdc.config and it is useful in future projects!

But for my project the C works at 64 bits except on Windows for 
the reason you gave. So by translating long in C to long in D it 
loses 32 bits but gains 64 bits on Windows. This is what I want.
Oct 17 2020