autofree: runtime invalid string free

[dy-tea]

Describe the bug

See below snippet. Runs fine without autofree.

Reproduction Steps

Run with v run test.v and note normal exit, run with v -autofree run test.v and note abort:

fn main() {
	b := byteptr(c'a')
	s := unsafe { b.vstring() }
	println(s)
}

Expected Behavior

Should exit normally as with the gc.

Current Behavior

❯ v -autofree run main.v
a
free(): invalid pointer
0x7fb6a0c550db: at ???: RUNTIME ERROR: abort() called

gdb output:

a
free(): invalid pointer

Program received signal SIGABRT, Aborted.
__pthread_kill_implementation (threadid=<optimized out>, signo=6, no_tid=0) at pthread_kill.c:44
44	      return INTERNAL_SYSCALL_ERROR_P (ret) ? INTERNAL_SYSCALL_ERRNO (ret) : 0;
(gdb) bt
#0  __pthread_kill_implementation (threadid=<optimized out>, signo=6, no_tid=0) at pthread_kill.c:44
#1  __pthread_kill_internal (threadid=<optimized out>, signo=6) at pthread_kill.c:89
#2  __GI___pthread_kill (threadid=<optimized out>, signo=signo@entry=6) at pthread_kill.c:100
#3  0x00007ffff7d787c8 in __GI_raise (sig=sig@entry=6) at ../sysdeps/posix/raise.c:26
#4  0x00007ffff7d5960d in __GI_abort () at abort.c:77
#5  0x00007ffff7d5a8c0 in __libc_message_impl (fmt=fmt@entry=0x7ffff7f0cd63 "%s\n")
    at ../sysdeps/posix/libc_fatal.c:138
#6  0x00007ffff7de8ca7 in malloc_printerr (str=<optimized out>) at malloc.c:5892
#7  0x00007ffff7de8cc1 in malloc_printerr_tail (str=<optimized out>) at malloc.c:5909
#8  0x000000000060b589 in _v_free () at /tmp/v_1000/main.tmp.c:4030
#9  0x0000000000610615 in string_free () at /tmp/v_1000/main.tmp.c:5378
#10 0x0000000000614262 in main__main () at /tmp/v_1000/main.tmp.c:6148
#11 0x000000000061449b in main () at /tmp/v_1000/main.tmp.c:6184

main function:

VV_LOC void main__main(void) {
	byteptr b = ((byteptr)("a"));
	string s = byteptr_vstring(b);
	println(s);
	string_free(&s); // autofreed var main false
}

Possible Solution

No response

Additional Information/Context

No response

V version

V 0.4.11 487feb9

Environment details (OS name and version, etc.)

V full version	V 0.4.11 344f7cc.487feb9
OS	linux, "CachyOS"
Processor	16 cpus, 64bit, little endian, AMD Ryzen 7 5700G with Radeon Graphics
Memory	5.82GB/13.55GB
V executable	/home/dylan/Repos/v/v
V last modified time	2025-09-02 14:05:13
V home dir	OK, value: /home/dylan/Repos/v
VMODULES	OK, value: /home/dylan/.vmodules
VTMP	OK, value: /tmp/v_1000
Current working dir	OK, value: /home/dylan
Git version	git version 2.51.0
V git status	weekly.2025.36-dirty (2 commit(s) behind V master)
.git/config present	true
cc version	cc (GCC) 15.2.1 20250813
gcc version	gcc (GCC) 15.2.1 20250813
clang version	clang version 20.1.8
tcc version	tcc version 0.9.28rc 2025-02-13 HEAD@f8bd136d (x86_64 Linux)
tcc git status	thirdparty-linux-amd64 696c1d84
emcc version	N/A
glibc version	ldd (GNU libc) 2.42

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[huly-for-github]

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