��

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

I'm stuck.�� The FFI64 plugin is way beyond my comprehension.

// microclang.c

typedef struct {

�� const void *ptr_data[2];

�� unsigned int_data;

} CXSourceLocation;

/**

��* \brief Identifies a half-open character range in the source code.

��*

��* Use clang_getRangeStart() and clang_getRangeEnd() to retrieve the

��* starting and end locations from a source range, respectively.

��*/

typedef struct {

�� const void *ptr_data[2];

�� unsigned begin_int_data;

�� unsigned end_int_data;

} CXSourceRange;

const char* first = "first_pointer";

const char* second = "second_pointer";

// return a fake range with non zero data

CXSourceRange clang_getArbitraryRange()

{

�� CXSourceRange range = {0};

�� range.ptr_data[0] = (void*)first;

�� range.ptr_data[1] = (void*)second;

�� range.begin_int_data = 17;

�� range.end_int_data = 24;

�� return range;

}

// Actual clang function - range is always zero'd here despite having values in the image

CXSourceLocation clang_getRangeStart(CXSourceRange range) {

�� // Special decoding for CXSourceLocations for CXLoadedDiagnostics.

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

�� �� CXSourceLocation Result = { { range.ptr_data[0], nullptr }, 0 };

�� �� return Result; �� ��

�� }

����

�� CXSourceLocation Result = { { range.ptr_data[0], range.ptr_data[1] },

�� �� range.begin_int_data };

�� return Result;

}