• tcak (45/45) Apr 22 2021 string fileContent = "";
• tcak (5/5) Apr 22 2021 In other parts of the code, concatenation operations are all
• Adam D. Ruppe (1/1) Apr 22 2021 Are there any other threads in your program?
• Adam D. Ruppe (2/5) Apr 22 2021 Oh and *where* is that positions variable defined?
• tcak (12/17) Apr 22 2021 I am doing OpenCL programming. CPU side is single threaded.
• Adam D. Ruppe (9/12) Apr 22 2021 The question of where is to see if it was CTFE allocated or
• Imperatorn (2/5) Apr 23 2021 Do you have a minimal reproducible test case? 🤔

tcak <tcak gmail.com> writes:

string fileContent = "";

...

writeln(ri, ": debug 1");
foreach(i; 0..dim)
{
	if( i > 0 ){ fileContent ~= "\t"; }

	writeln(ri, ": debug 1.1: ", ri*dim + i, ": ", positions[ ri*dim 
+ i ]);

	fileContent ~= to!string(positions[ ri*dim + i ]);

	writeln(ri, ": debug 1.2: ", ri*dim + i, ": ", positions[ ri*dim 
+ i ]);
}

---------

On line "fileContent ~= ...", I get a segmentation fault.

"positions" array is defined as auto positions = new float[ 100 
]; So, I am 100% sure, it is not out of range. "ri*dim + 1" is 
not a big number at all.

...
4: debug 1.1: 9: 0.271075
4: debug 1.2: 9: 0.271075
4: debug 2
4: debug 2.1: 4
4: debug 3
4: debug 4
5: debug 1
5: debug 1.1: 10: 0.884978
5: debug 1.2: 10: 0.884978
5: debug 1.1: 11: 0.813104
Segmentation fault
...

I have compiled the code with "-g" flag and ran it with GNU 
debugger. It gives following:

Thread 1 "dataspace" received signal SIGSEGV, Segmentation fault.
0x00005555556ca286 in 
_D2gc4impl12conservativeQw3Gcx10smallAllocMFNbmKmkxC8TypeInfoZPv 
()


So, there is a problem about small allocation. I remember I had 
this problem before in another project.

I have enough free ram. htop shows 3.96 GiB of 8 GiB is used only 
and swap is not in use.

DMD64 D Compiler v2.094.0

Is this error related to me? Is it a programmer error? Is it a 
bug? Am I doing something wrong? This is a compiler related 
operation (string concatenation), and I assume/expect that it 
would work without a problem.

tcak <tcak gmail.com> writes:

In other parts of the code, concatenation operations are all 
failing with same error. I need guidance to get out of this 
situation. My assumption was that as long as there is empty heap 
memory, concatenation operation would succeed always. But, it 
doesn't seem like so.

Adam D. Ruppe <destructionator gmail.com> writes:

Are there any other threads in your program?

Adam D. Ruppe <destructionator gmail.com> writes:

On Thursday, 22 April 2021 at 21:15:48 UTC, tcak wrote:
 "positions" array is defined as auto positions = new float[ 100 
 ]; So, I am 100% sure, it is not out of range. "ri*dim + 1" is 
 not a big number at all.

Oh and *where* is that positions variable defined?

tcak <tcak gmail.com> writes:

On Friday, 23 April 2021 at 00:30:02 UTC, Adam D. Ruppe wrote:
 On Thursday, 22 April 2021 at 21:15:48 UTC, tcak wrote:
 "positions" array is defined as auto positions = new float[ 
 100 ]; So, I am 100% sure, it is not out of range. "ri*dim + 
 1" is not a big number at all.

 Oh and *where* is that positions variable defined?

I am doing OpenCL programming. CPU side is single threaded.

As far as I see, it is not related to that array or indices at 
all. After running for a short time, if a piece of code does any 
string/char or byte array concatenation at all, all of them cause 
segmentation fault with error:

_D2gc4impl12conservativeQw3Gcx10smallAllocMFNbmKmkxC8TypeInfoZPv 
()

When I comment out those piece of codes, there is no error.

If there is no known situation that would cause this, I will need 
to update codes to C-style pre-allocate buffer and copy inside it 
instead of concatenating data.

Adam D. Ruppe <destructionator gmail.com> writes:

On Friday, 23 April 2021 at 00:44:58 UTC, tcak wrote:
 As far as I see, it is not related to that array or indices at 
 all.

The question of where is to see if it was CTFE allocated or 
runtime allocated. I don't think it should make a difference here 
but idk.

 If there is no known situation that would cause this

druntime not being initialized is the only situation I know of 
that causes this directly. Otherwise memory corruption or race 
condition of some sort, hence why i was wondering about threads.

But I don't think it is uninitialized druntime unless that new 
happened at ctfe or something.

Imperatorn <johan_forsberg_86 hotmail.com> writes:

On Thursday, 22 April 2021 at 21:15:48 UTC, tcak wrote:
 string fileContent = "";

 ...

 [...]

Do you have a minimal reproducible test case? 🤔