• kris (3/3) Mar 29 2006 "incompatible types for ((cast(void*)(src)) + (cast(void*)*(p))):
• Tom S (4/8) Mar 30 2006 Not really a bug, though the error message might be 'cannot add two
• Unknown W. Brackets (5/9) Mar 30 2006 Shouldn't you make them ubytes or something first?
• kris (20/33) Mar 30 2006 Yeah ... it is a bit odd :)
• Unknown W. Brackets (4/45) Mar 31 2006 Why are you using a pointer type for ptr? That's just asking for

kris <foo bar.com> writes:

"incompatible types for ((cast(void*)(src)) + (cast(void*)*(p))): 
'void*' and 'void*'"

:)

Tom S <h3r3tic remove.mat.uni.torun.pl> writes:

kris wrote:
 "incompatible types for ((cast(void*)(src)) + (cast(void*)*(p))): 
 'void*' and 'void*'"
 
 :)

Not really a bug, though the error message might be 'cannot add two 
pointers' or something alike :)


Tomasz Stachowiak  /+ a.k.a. h3r3tic +/

"Unknown W. Brackets" <unknown simplemachines.org> writes:

Shouldn't you make them ubytes or something first?

Also, forgive my ignorance, but for what good reason would you add two 
pointers?  Subtracting is great and wonderful... adding a pointer and an 
int is amazing...  but adding pointers?

-[Unknown]


 "incompatible types for ((cast(void*)(src)) + (cast(void*)*(p))): 
 'void*' and 'void*'"
 
 :)

kris <foo bar.com> writes:

Unknown W. Brackets wrote:
 Shouldn't you make them ubytes or something first?
 
 Also, forgive my ignorance, but for what good reason would you add two 
 pointers?  Subtracting is great and wonderful... adding a pointer and an 
 int is amazing...  but adding pointers?
 
 -[Unknown]
 
 
 "incompatible types for ((cast(void*)(src)) + (cast(void*)*(p))): 
 'void*' and 'void*'"

 :)


Yeah ... it is a bit odd :)

This came up when serializing & deserializing arrays. I ended up 
modifying each array pointer|length pair to be an offset|length pair 
instead, and then writing that pair as though it were an ordinary field 
(like a long int).

When deserializing, the offset|length pair gets converted back to a 
pointer|length pair by adding a base-address to the offset. Hence, we 
end up with what /looks/ like the addition of two pointers.

The decoding looked something like this:

void* base_address;
void[]* p = address_of_encoded_array;
*p = (base_address + (*p).ptr)[0 .. (*p).length];

where (*p).ptr is actually the encoded offset, rather than a pointer. 
That's where DMD tossed the amusing "void* is incompatible with void*" 
error. This was fixed by removing the .ptr syntax, causing DMD to 
extract the offset via implicit type-casting instead (matching the void* 
on the LHS).

The approach is a bit grubby, but that's ok.

- Kris

"Unknown W. Brackets" <unknown simplemachines.org> writes:

Why are you using a pointer type for ptr?  That's just asking for 
trouble, imho... why not use a ptrdiff_t (which is designed for this 
very purpose, afaik)?  Or do you hate those types for some reason?

-[Unknown]


 Unknown W. Brackets wrote:
 Shouldn't you make them ubytes or something first?

 Also, forgive my ignorance, but for what good reason would you add two 
 pointers?  Subtracting is great and wonderful... adding a pointer and 
 an int is amazing...  but adding pointers?

 -[Unknown]


 "incompatible types for ((cast(void*)(src)) + (cast(void*)*(p))): 
 'void*' and 'void*'"

 :)


 
 Yeah ... it is a bit odd :)
 
 This came up when serializing & deserializing arrays. I ended up 
 modifying each array pointer|length pair to be an offset|length pair 
 instead, and then writing that pair as though it were an ordinary field 
 (like a long int).
 
 When deserializing, the offset|length pair gets converted back to a 
 pointer|length pair by adding a base-address to the offset. Hence, we 
 end up with what /looks/ like the addition of two pointers.
 
 The decoding looked something like this:
 
 void* base_address;
 void[]* p = address_of_encoded_array;
 *p = (base_address + (*p).ptr)[0 .. (*p).length];
 
 where (*p).ptr is actually the encoded offset, rather than a pointer. 
 That's where DMD tossed the amusing "void* is incompatible with void*" 
 error. This was fixed by removing the .ptr syntax, causing DMD to 
 extract the offset via implicit type-casting instead (matching the void* 
 on the LHS).
 
 The approach is a bit grubby, but that's ok.
 
 - Kris