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From: "iam at datacompboy dot ru" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libgcc/106949] New: Memory leak using VLA with -fsplit-stack
Date: Thu, 15 Sep 2022 08:18:05 +0000
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X-Bugzilla-Version: 11.2.0
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D106949

            Bug ID: 106949
           Summary: Memory leak using VLA with -fsplit-stack
           Product: gcc
           Version: 11.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libgcc
          Assignee: unassigned at gcc dot gnu.org
          Reporter: iam at datacompboy dot ru
  Target Milestone: ---

Created attachment 53575
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D53575&action=3Dedit
minimal repro case

Having a function with couple of VLA arrays enough to cause a memory leak.

If you run the function in a loop, memory leak only grows.

```
$ gcc -fsplit-stack -g b.c && valgrind ./a.out
=3D=3D6861=3D=3D HEAP SUMMARY:
=3D=3D6861=3D=3D     in use at exit: 20,040 bytes in 2 blocks
=3D=3D6861=3D=3D   total heap usage: 2 allocs, 0 frees, 20,040 bytes alloca=
ted
=3D=3D6861=3D=3D
=3D=3D6861=3D=3D LEAK SUMMARY:
=3D=3D6861=3D=3D    definitely lost: 24 bytes in 1 blocks
=3D=3D6861=3D=3D    indirectly lost: 20,016 bytes in 1 blocks
```

With a loop running function 10k times:
```
$ gcc -fsplit-stack -g c.c && valgrind ./a.out
=3D=3D6931=3D=3D HEAP SUMMARY:
=3D=3D6931=3D=3D     in use at exit: 569,801,800 bytes in 32,162 blocks
=3D=3D6931=3D=3D   total heap usage: 32,162 allocs, 0 frees, 569,801,800 by=
tes
allocated
=3D=3D6931=3D=3D
=3D=3D6931=3D=3D LEAK SUMMARY:
=3D=3D6931=3D=3D    definitely lost: 385,944 bytes in 16,081 blocks
=3D=3D6931=3D=3D    indirectly lost: 569,121,904 bytes in 16,072 blocks
=3D=3D6931=3D=3D      possibly lost: 293,952 bytes in 9 blocks
```=