If you look into win32.c/.h and unwind those functions, you'll find that they use a custom (pseudo-C++ style) allocator that uses different pools for different threads. (iThreads, that is.)

But for that to work properly, it needs to be initialised and as you are not instantiating an interpreter in your thread(s), you are not getting that initialisation done.

Basically, by using the perl environment to compile (what is essentially) pure C code, you're just opening yourself to a whole world of hurt. It, the Perl environment, simply isn't designed to be used that way.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

If you do this on win32 I don't get this "double free" error

#include <pthread.h>

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

#include "EXTERN.h"
...
[download]

I changed it to


#include <pthread.h>

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

#include "EXTERN.h"
#include "perl.h"
#include "XSUB.h"
#include "ppport.h"

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]


And the problem still here: crash on each run

And gdb output looks not very usefull


(gdb) r t.pl
Starting program: C:\Perl64\bin\perl.exe t.pl
[New Thread 17748.0x6114]
[New Thread 17748.0x61f8]
thread: Just another XS hacker
warning: Critical error detected c0000374


Program received signal SIGTRAP, Trace/breakpoint trap.
[Switching to Thread 17748.0x61f8]
0x00000000770d40d0 in ntdll!RtlUnhandledExceptionFilter ()
   from C:\WINDOWS\SYSTEM32\ntdll.dll
(gdb) bt
#0  0x00000000770d40d0 in ntdll!RtlUnhandledExceptionFilter ()
   from C:\WINDOWS\SYSTEM32\ntdll.dll
#1  0x00000000770d4746 in ntdll!EtwEnumerateProcessRegGuids ()
   from C:\WINDOWS\SYSTEM32\ntdll.dll
#2  0x00000000770d5952 in ntdll!RtlQueryProcessLockInformation ()
   from C:\WINDOWS\SYSTEM32\ntdll.dll
#3  0x00000000770d7604 in ntdll!RtlLogStackBackTrace ()
   from C:\WINDOWS\SYSTEM32\ntdll.dll
#4  0x000000007707dc47 in ntdll!RtlIsDosDeviceName_U ()
   from C:\WINDOWS\SYSTEM32\ntdll.dll
Backtrace stopped: previous frame inner to this frame (corrupt stack?)
(gdb)
[download]

FWIW its  gcc -E   Preprocess only; do not compile, assemble or link

But yes perl does redefine these things, http://perl5.git.perl.org/perl.git/blob/HEAD:/XSUB.h#l563

563 #    define malloc              PerlMem_malloc
564 #    define realloc             PerlMem_realloc
565 #    define free                PerlMem_free
[download]

But yes perl does redefine these things, ...

The problem is that those also get redefined at various points. See win32\win32iop.h. Sometimes, multiple times depending upon where you are in the source code.

And the allocator used under Windows is a custom allocator. See win32\vmem.h. (Though that is also dependent upon build-time options...)

It's all very convoluted to work out exactly what is being compiled.

---

With the rise and rise of 'Social' network sites: 'Computers are making people easier to use everyday'

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

The problem is that those also get redefined at various points

Aaaah ... it seems to be the old "#undef free" trick that's needed here.
The following rendition works fine for me on Strawberry:

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

You can probably disregard my other post of a few minutes ago.

(By undeffing free, we get to call the free() that we want, not the the free() that perl defined for us.)

Cheers,
Rob