GC Memory leak about ldc HOT 10 OPEN

If to use -betterC switch then leak disappears

echo "extern(C) int main() { return 0; }" > test.d
ldc test.d -betterC
valgrind ./test

Outputs:

==41353== Memcheck, a memory error detector
==41353== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et al.
==41353== Using Valgrind-3.22.0 and LibVEX; rerun with -h for copyright info
==41353== Command: ./test
==41353== 
==41353== 
==41353== HEAP SUMMARY:
==41353==     in use at exit: 0 bytes in 0 blocks
==41353==   total heap usage: 0 allocs, 0 frees, 0 bytes allocated
==41353== 
==41353== All heap blocks were freed -- no leaks are possible
==41353== 
==41353== For lists of detected and suppressed errors, rerun with: -s
==41353== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

from ldc.

and sanitizers? (address, memory, thread)

from ldc.

Havent tested, not sure how to though

from ldc.

Havent tested, not sure how to though

Try:

$> export ASAN_OPTIONS=abort_on_error=0:fast_unwind_on_malloc=0:detect_leaks=1 UBSAN_OPTIONS=print_stacktrace=1
$> ldc2 hello.d -fsanitize=memory
$> ./hello
## Output empty/none or stacktrce?

Reference

• Memory error checking in C and C++: Comparing Sanitizers and Valgrind - RedHat

from ldc.

Nothing
But running resulting binary with valgrind kills my pc

from ldc.

isn't leaking intentional in DMD and LDC without -lowmem?
i misunderstood, never mind.

from ldc.

These are probably just harmless little leaks in upstream druntime, where nobody bothered cleaning up a few bytes. E.g., for

==39912== 32 bytes in 1 blocks are possibly lost in loss record 3 of 4
==39912== at 0x4843788: malloc (vg_replace_malloc.c:442)
==39912== by 0x4D3B7CA: core.internal.gc.impl.conservative.gc.initialize() (in /usr/lib/libdruntime-ldc-shared.so.107.1

See https://github.com/dlang/dmd/blob/274eec89f4ce7f34a1776e3ac1b1e9c82de90811/druntime/src/core/internal/gc/impl/conservative/gc.d#L142 - that ConservativeGC object itself is malloc'd during runtime/GC initialization and most likely never freed.

from ldc.

Does this leak occur on another system and/or libc?
Because on the Alpine I didn't have the same problem.

from ldc.

I have no way of checking other platforms

Also not sure about libc, like, what I do with it?

from ldc.

Also not sure about libc, like, what I do with it?

I cited libc because Alpine uses musl and not glibc.
It would be interesting to know if this applies only to glibc, or even only to archlinux.

If you have docker installed, you can test it:

# ldc2 master - upstream (musl fixed)
$ docker pull kassany/alpine-ldc2
$ docker run --rm -it -v $(pwd):/app -w /app kassany/alpine-ldc2:latest ash

# for musl can build `ldc2/ldmd2 -static foo.d` (libunwind-static already installed)
# run valgrind (your host) in static-foo.

from ldc.