malloc error when trying to assign the returned pointer to a struct field

[Kagamin]

On Friday, 8 September 2023 at 13:32:00 UTC, rempas wrote:
> On Friday, 8 September 2023 at 13:05:47 UTC, evilrat wrote:
>> ```d
>> import core.stdc.stdlib;
>> import core.stdc.stdio;
>>
>> alias u64 = ulong;
>> alias i64 = long;
>>
>> struct Vec(T) {
>> private:
>>   T* _ptr = null; // The pointer to the data
>>   u64 _cap = 0;   // Total amount of elements (not bytes) we 
>> can store
>>   u64 _len = 0;
>>
>> public:
>>   /* Create a vector by just allocating memory for it. The 
>> null terminator is not set for
>>      strings as, the vector is considered empty and we should  
>> first push something to it
>>      in order to use it! */
>>   this(i64 size) {
>>     this._len = 0;
>>     this._cap = size;
>>
>>     static if (is(T == char)) { size += 1; } // Additional 
>> space for the null terminator
>>     this._ptr = cast(T*)malloc(size);
>>   }
>>
>>   ref T opIndex(size_t idx) { return _ptr[idx]; }
>> }
>>
>> extern(C)
>> void main()
>> //unittest
>> {
>>     enum el = 3;
>>     auto vec = Vec!char(10);
>>     assert(vec._ptr);
>>     vec[el] = 'h';
>>     assert(vec[el] == 'h');
>>     printf("ptr = %p\n", vec._ptr);
>>     printf("vec ptr = %p\n", &vec[el]);
>>     printf("vec local = %p\n", &vec);
>>     printf("vec[%d] = %c\n", el, vec[el]);
>>     foreach (i; 0..vec._cap) {
>>       printf("-");
>>     }
>>     printf("\n");
>>     foreach (i; 0..vec._cap) {
>>       printf("%d", vec[i]);
>>     }
>>     printf("\n");
>>     printf("run ok\n");
>> }
>> ```
>>
>> ldc2 -betterC -run membug.d
>>
>> output
>>
>> ```
>> ptr = 0x55cb701de2a0
>> vec ptr = 0x55cb701de2a3
>> vec local = 0x7fffa1542258
>> vec[3] = h
>> ----------
>> 000104000000
>> run ok
>> ```
>
> I have made a search on the web and I found out one thread that 
> pointed out that it may be a Glibc error. However, because like 
> I said the problem only happens when I assign the returned 
> value to the `_ptr` field, I just wanted to post here in case 
> someone has a similar experience and if it's a compiler bug in 
> which case, we should report it.

Did you run this example program above? Does it crash?