On 22 November 2017 at 21:59, Ben Coman <btc@openinworld.com> wrote:

On 22 November 2017 at 13:38, Todd Blanchard <tblanchard@mac.com> wrote:
��
I've been trying to track this down for a couple weeks now.

I have concluded that structs passed by value to functions on the 64 bit VM are not properly populated.�� The struct's memory is all zero'd.

I found this while trying to work with LibClang and found that functions that fetched code locations from code ranges always returned invalid zero'd locations.�� After spending some time with lldb I have traced the problem into the native code and found that the argument is not correct.

I've carved out the wee bit of clang to reproduce this in a tiny library.

The gist of it is below and the entire file is included.�� Basically the struct passed to the function clang_getRangeStart is zero'd memory regardless of the data I send from the image side.

The build command I used on sierra is��clang -shared -undefined dynamic_lookup -o microclang.dylib microclang.c

On Ubuntu 16.04 I used...
$ clang -shared -fPIC -o libmicroclang.so microclang.c

$��clang test.c -L. -l microclang
�� test.c:6:53: error: no member named 'begin_int_data' in 'CXSourceLocation'
�� if(clang_getRangeStart(clang_getArbitraryRange()).begin_int_data == 0)��

I presume you meant...
�� if(clang_getRangeStart(clang_getArbitraryRange()).int_data == 0)��
so correcting and continuing...

$ clang test.c -L. -l microclang
$ LD_LIBRARY_PATH=. ./a.out
That failed

So I'm not sure how to proceed.��
I was expecting that would work while Pharo failed.

Now interestingly...
$ clang test.c microlang.c
$ ./a.out
That worked

So it seems a similar problem exists outside our FFI.��

cheers -ben

P.S. I refactored you code to extract a header file (attached)

The issue is still beyond my ken, but I've made some progress towards isolating/understanding the issue.

Attached zip exploded here for easy reference...

___microlang.h___

typedef unsigned�� uintptr_t;

typedef struct {

�� const void *ptr_data[2];

} CXSourceRange_;

CXSourceRange_ clang_getArbitraryRange_();

int clang_getRangeEnd_(CXSourceRange_ range);

___microclang.c___

#include "microclang.h"

const char* libraryString = "library_pointer";

CXSourceRange_ clang_getArbitraryRange_()

{�� CXSourceRange_ range = {0};

�� range.ptr_data[0] = (void*)libraryString;

�� return range;

}

int clang_getRangeEnd_(CXSourceRange_ range)

{�� // Special decoding for CXSourceLocations for CXLoadedDiagnostics.

�� if ((uintptr_t)range.ptr_data[0] & 0x1)

�� {�� return 0;�� }

�� else

�� {�� return 1;�� }

}

___test.c___

#include <stdio.h>

#include "microclang.h"

const char* localString =�� "local_pointer";

void test( CXSourceRange_ range, char *note )

{�� int result = clang_getRangeEnd_(range);

�� if(result == 0)

�� {�� printf("That failed (%s)\n", note); }

�� else

�� {�� printf("That worked (%s)\n", note); }

}

int main()

{�� CXSourceRange_ range1 = clang_getArbitraryRange_();

�� test(range1, "library string");

�� CXSourceRange_ range2 = {0};

�� range2.ptr_data[0] = (void*)localString;

�� test(range2, "local string");

}

___Makefile___

default: clean static shared

clean:

�� rm -f *so *App

�� @echo

shared:

�� clang -g -o libmicroclang.so -shared -fPIC microclang.c

�� clang -g -o sharedApp test.c -L. -lmicroclang

�� LD_LIBRARY_PATH=. ./sharedApp

�� @echo

static:

�� clang -g -o staticApp test.c microclang.c

�� ./staticApp

�� @echo

Now running...

$ make > report

gives...

___report___

rm -f *so *App

clang -g -o staticApp test.c microclang.c

./staticApp

That worked (library string)

That worked (local string)

clang -g -o libmicroclang.so -shared -fPIC microclang.c

clang -g -o sharedApp test.c -L. -lmicroclang

LD_LIBRARY_PATH=. ./sharedApp

That failed (library string)

That worked (local string)

cheers -ben