Re: this is null
On Sunday, 10 March 2019 at 14:25:56 UTC, spir wrote: There is a typo in this instruction: T* ptr = this.list.getFisrtFreeOrAdd(memViewLen).getPtr!T(); ^^ rs (may this explain your null? the compiler should complain) diniz Good catch! But I have the same typo within the definition of the method. I believe DMD screams about undefined method if it happens.
Re: this is null
On 09/03/2019 21:10, ANtlord via Digitalmars-d-learn wrote: On Saturday, 9 March 2019 at 20:04:53 UTC, Paul Backus wrote: You can end up with a null `this` reference if you dereference a null pointer to a struct and then call a method on the result. For example: I can but my reference is not null before calling. Take a look at the line of code [0]. There is a check before the line. https://github.com/ANtlord/deadmemory/blob/master/src/deadmemory/mem.d#L20 [0] There is a typo in this instruction: T* ptr = this.list.getFisrtFreeOrAdd(memViewLen).getPtr!T(); ^^ rs (may this explain your null? the compiler should complain) diniz
Re: this is null
On Saturday, 9 March 2019 at 21:00:51 UTC, Ali Çehreli wrote: I haven't run the code but which pointer is null? Try adding I mean `this` by "this" word. You can see that `this` is null if you run gdb and before that line make `p/x this` [0] this check as well: auto node = this.list.getFisrtFreeOrAdd(memViewLen); assert(node !is null); I get segfault in `getFisrtFreeOrAdd` method. Before the line I have an assertion [1]. It looks like the program misses (I have no idea how) `list` object while calling its method `getFisrtFreeOrAdd`. [0] https://github.com/ANtlord/deadmemory/blob/master/src/deadmemory/freelist.d#L56 [1] https://github.com/ANtlord/deadmemory/blob/master/src/deadmemory/mem.d#L19
Re: this is null
On 03/09/2019 12:10 PM, ANtlord wrote: On Saturday, 9 March 2019 at 20:04:53 UTC, Paul Backus wrote: You can end up with a null `this` reference if you dereference a null pointer to a struct and then call a method on the result. For example: I can but my reference is not null before calling. Take a look at the line of code [0]. There is a check before the line. https://github.com/ANtlord/deadmemory/blob/master/src/deadmemory/mem.d#L20 [0] I haven't run the code but which pointer is null? Try adding this check as well: auto node = this.list.getFisrtFreeOrAdd(memViewLen); assert(node !is null); Ali
Re: this is null
On Saturday, 9 March 2019 at 20:04:53 UTC, Paul Backus wrote:
struct S
{
bool isThisNull() { return &this is null; }
}
void main()
{
import.std.stdio;
S* p = null;
writeln((*p).isThisNull); // true
}
Interactive version: https://run.dlang.io/is/fgT2rS
Anyway, thank you! I didn't know about the feature.
Re: this is null
On Saturday, 9 March 2019 at 20:04:53 UTC, Paul Backus wrote: You can end up with a null `this` reference if you dereference a null pointer to a struct and then call a method on the result. For example: I can but my reference is not null before calling. Take a look at the line of code [0]. There is a check before the line. https://github.com/ANtlord/deadmemory/blob/master/src/deadmemory/mem.d#L20 [0]
Re: this is null
On Saturday, 9 March 2019 at 19:18:38 UTC, ANtlord wrote:
Hello everyone! I've encountered the problem which I already
encountered before. Unfortunately, I had no time in the
previous time to report and to talk about it. So I decided to
play making my own "malloc" function in pure D (betterC) at
this time. And I encountered the issue one more time. `this`
can be null. How? Please take a look at my project [0]. It gets
the current heap break and tries to increase via a free list.
So the segfault I meet happens there [1]. Tell me, please. What
do I wrong?
[0] https://github.com/ANtlord/deadmemory
[1]
https://github.com/ANtlord/deadmemory/blob/master/src/deadmemory/freelist.d#L56
You can end up with a null `this` reference if you dereference a
null pointer to a struct and then call a method on the result.
For example:
struct S
{
bool isThisNull() { return &this is null; }
}
void main()
{
import.std.stdio;
S* p = null;
writeln((*p).isThisNull); // true
}
Interactive version: https://run.dlang.io/is/fgT2rS
