On Alpine, I see:

```
 stdout: 
[[0.001s][trace][os] active_processor_count: using dynamic path (forced) - configured processors: 16
[0.001s][trace][os] active_processor_count: sched_getaffinity processor count: 16
NMT Block at 0x00007fc5a35db9f0, corruption at: 0x00007fc5a35db9f0: 
0x00007fc5a35db970:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35db980:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35db990:   f8 a1 c8 1b ea 55 00 00 00 00 00 00 00 c0 00 00
0x00007fc5a35db9a0:   00 a4 c8 1b ea 55 00 00 01 00 00 00 00 c0 00 00
0x00007fc5a35db9b0:   d8 a3 c8 1b ea 55 00 00 1d 00 00 00 00 a0 00 00
0x00007fc5a35db9c0:   2d 63 70 00 00 00 00 00 08 00 00 00 00 61 01 00
0x00007fc5a35db9d0:   2d 76 65 72 73 69 6f 6e 00 00 00 00 00 82 02 00
0x00007fc5a35db9e0:   2d 73 65 72 76 65 72 00 00 00 00 00 00 83 03 00
0x00007fc5a35db9f0:   2d 63 6c 69 65 6e 74 00 00 00 00 00 00 84 04 00
0x00007fc5a35dba00:   ff ff 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35dba10:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35dba20:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35dba30:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35dba40:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35dba50:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
0x00007fc5a35dba60:   00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 
# To suppress the following error report, specify this argument
# after -XX: or in .hotspotrc:  SuppressErrorAt=/mallocTracker.cpp:151
#
# A fatal error has been detected by the Java Runtime Environment:
#
#  Internal Error (/home/ubuntu/client_home/workspace/build-user-branch-linux_alpine_x86_64/SapMachine/src/hotspot/share/services/mallocTracker.cpp:151), pid=219496, tid=219512
#  fatal error: NMT corruption: Block at 0x00007fc5a35db9f0: header canary broken
#
# JRE version:  (20.0) (fastdebug build )
# Java VM: OpenJDK 64-Bit Server VM (fastdebug 20-snapshotbeta-2022-06-29, mixed mode, sharing, tiered, unknown gc, linux-amd64)
# Core dump will be written. Default location: Core dumps may be processed with "/usr/share/apport/apport -p%p -s%s -c%c -d%d -P%P -u%u -g%g -- %E" (or dumping to /home/ubuntu/client_home/workspace/build-user-branch-linux_alpine_x86_64/test_report_hotspot/JTwork/scratch/8/core.219496)
#
```

Reason:

In `os::Linux::active_processor_count()`, we use the CPU_xxx macros to manage sets of CPU information.

muslc defines those macros to call `calloc(3)` and `free(3)`:

```
#define CPU_ALLOC(n) ((cpu_set_t *)calloc(1,CPU_ALLOC_SIZE(n)))
#define CPU_FREE(set) free(set)
```

whereas glibc uses intermediate functions:

```
#define __CPU_ALLOC(count) __sched_cpualloc (count)
#define __CPU_FREE(cpuset) __sched_cpufree (cpuset)
```

which in the end also takes from C-heap, but those calls are not inlined.

So, on muslc we call `calloc()` and `free()`. Call happens inside the `os::Linux` namespace, `free()` resolves to `os::free()`. We have no wrapper in os for calloc though, so `calloc()` calls into muslc right away.

That means we have raw ::malloc() -> os::free(), which is unbalanced. Raw `::malloc()` does not write the header `os::free()` expects. If NMT is on, we assert now, because NMT does not find its header in os::free(). 

This can be very easily reproduced by starting an Alpine VM with NMT on (or, a debug VM) and ` -XX:+UnlockDiagnosticVMOptions -XX:+UseCpuAllocPath`.

The position of the musl devs is that "calloc" and "free" are reserved words in C, and should not be used [1]. I think they are right. The way we reuse known C- and Posix symbol names in the os namespace has bitten me in the past in similar cases.

[1] https://www.openwall.com/lists/musl/2022/06/29/3