Crash occures only on Windows.
Here is a simple example

My.xs
#include <pthread.h>
#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "ppport.h"

void *thread(void *arg) {
    char *msg = (char*)arg;
    printf("thread: %s\n", msg);
    free(msg);
    return NULL;
}

MODULE = My    PACKAGE = My

void
test_thread(char *msg)
    PPCODE:
        char *thread_arg = malloc((strlen(msg)+1)*sizeof(char));
        strcpy(thread_arg, msg);
        pthread_t tid;
        pthread_create(&tid, NULL, thread, (void*)thread_arg);
        
        void *rv;
        pthread_join(tid, &rv);

[download]


lib/My.pm
package My;

use strict;
use XSLoader();
our $VERSION = 0.01;

XSLoader::load('My', $VERSION);

1;

[download]


Makefile.PL 
use ExtUtils::MakeMaker;

WriteMakefile(
    NAME           => 'My',
    VERSION_FROM   => 'lib/My.pm',
    LIBS           => ['-lpthread'],
);

[download]


t.pl 
use blib;
use My;

My::test_thread("Just another XS hacker");

[download]


This works on Linux and crashes on Windows. If I'll comment free(msg) it will also work on Windows.
What's wrong here?

UPD:
All files of the example in one place: https://github.com/olegwtf/sandbox/tree/master/xs-free-windows-problem

In reply to XS: free() outside of the main thread causes crash on Windows by OlegG

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