program bellow crashed // dmd -m32 -release -O gctest.d import std, core.memory; void main() { long r = 0; // using results = dont drop code for(int i = 0; i < 1000; i++) { auto x = new int[10000000]; r += x.sum(); } write( r ); } C:\content\downloadz\dlang>gctest.exe core.exception.OutOfMemoryError@src\core\exception.d(702): Memory allocation failed ---------------- with -m64 no crashes but prog has more memory than 2GB. it cannot be false positive coz array contains all 0s (int.init) imo something wrong with gc-roots or gc-marks. code by LDC works fine.
Windows Server 2019 (x64) DMD 2.086.0 LDC 1.16.0-beta2
It can be false positive, see issue 15723
maybe u right. imo gc shouldnt scan all data segment for pointers: when we assign to some globals some pointers or explicitly called GC.addRange/addRoot. and when I transfer something to C(or others)-libs.. well, its my responsibility only, not compiler or GC
I don't think that it can be false positives. Adding a GC.collect() call will clean up the allocations; so the issue must rather be that collection is not started for some reason. See also original forum discussion: https://forum.dlang.org/thread/obkpctudtnnfojrbrwiv@forum.dlang.org
To avoid false pointers in the heap and the data segment, use --DRT-gcopt=gc:precise --DRT-scanDataSeg=precise With these the program runs to completion.
(In reply to Rainer Schuetze from comment #5) > To avoid false pointers in the heap and the data segment, use > --DRT-gcopt=gc:precise --DRT-scanDataSeg=precise > > With these the program runs to completion. How does this square with the fact that calling GC.collect() inside the for loop also makes the program run to completion? Also, the array is initialized with 0, so any false false pointers would be invisible to the user code.
> How does this square with the fact that calling GC.collect() > inside the for loop also makes the program run to completion? When running GC.collect() after the allocation, you are changing the amount of memory that the GC overallocates before running the next collection (2 times the live memory at the time of the previous collection). This changes the probability of getting false pointers. > Also, the array is initialized with 0, so any false false pointers > would be invisible to the user code. The content of the int[] array is not scanned, the false pointers in the data segment (and the stack, -gx might help) are the issue here. These can pin the large allocations. Address randomization (ASLR) makes it rather unpredictable, too.