XEqualRegion() for Tk Aqua using __HIShapeEqual() using FindSymbol() hack

tkMacOSXRegion_excerpt.c

// FindSymbol() approach stolen from https://stackoverflow.com/a/21855885/4896937
// Adapted from:
// https://github.com/0xced/iOS-Artwork-Extractor/blob/master/Classes/FindSymbol.c
// Adapted from MoreAddrToSym / GetFunctionName()
// http://www.opensource.apple.com/source/openmpi/openmpi-8/openmpi/opal/mca/backtrace/darwin/MoreBacktrace/MoreDebugging/MoreAddrToSym.c
#include <mach-o/dyld.h>
#include <mach-o/nlist.h>
static void *FindSymbol(const struct mach_header *img, const char *symbol)
{
    if ((img == NULL) || (symbol == NULL))
        return NULL;

    // only 64bit supported
#if defined (__LP64__)

    if(img->magic != MH_MAGIC_64)
        // we currently only support Intel 64bit
        return NULL;

    struct mach_header_64 *image = (struct mach_header_64*) img;

    struct segment_command_64 *seg_linkedit = NULL;
    struct segment_command_64 *seg_text = NULL;
    struct symtab_command *symtab = NULL;
    unsigned int index;

    struct load_command *cmd = (struct load_command*)(image + 1);

    for (index = 0; index < image->ncmds; index += 1, cmd = (struct load_command*)((char*)cmd + cmd->cmdsize))
    {
        switch(cmd->cmd)
        {
            case LC_SEGMENT_64: {
                struct segment_command_64* segcmd = (struct segment_command_64*)cmd;
                if (!strcmp(segcmd->segname, SEG_TEXT))
                    seg_text = segcmd;
                else if (!strcmp(segcmd->segname, SEG_LINKEDIT))
                    seg_linkedit = segcmd;
                break;
            }

            case LC_SYMTAB:
                symtab = (struct symtab_command*)cmd;
                break;

            default:
                break;
        }
    }

    if ((seg_text == NULL) || (seg_linkedit == NULL) || (symtab == NULL))
        return NULL;

    unsigned long vm_slide = (unsigned long)image - (unsigned long)seg_text->vmaddr;
    unsigned long file_slide = ((unsigned long)seg_linkedit->vmaddr - (unsigned long)seg_text->vmaddr) - seg_linkedit->fileoff;
    struct nlist_64 *symbase = (struct nlist_64*)((unsigned long)image + (symtab->symoff + file_slide));
    char *strings = (char*)((unsigned long)image + (symtab->stroff + file_slide));
    struct nlist_64 *sym;

    for (index = 0, sym = symbase; index < symtab->nsyms; index += 1, sym += 1)
    {
        if (sym->n_un.n_strx != 0 && !strcmp(symbol, strings + sym->n_un.n_strx))
        {
            unsigned long address = vm_slide + sym->n_value;
            if (sym->n_desc & N_ARM_THUMB_DEF)
                return (void*)(address | 1);
            else
                return (void*)(address);
        }
    }   
#endif

    return NULL;
}
typedef Boolean (*HIShapeEqualFunc)(void const *inShape1, void const *inShape2);
Bool
XEqualRegion(
    void *srca,
    void *srcb)
{
    static HIShapeEqualFunc HIShapeEqual = NULL;
    if (HIShapeEqual == NULL) {
	const struct mach_header* img = NSAddImage(
		"/System/Library/Frameworks/ApplicationServices.framework/Versions/A/Frameworks/HIServices.framework/Versions/A/HIServices",
		NSADDIMAGE_OPTION_NONE);
	const char *mangled_name ="__ZL14__HIShapeEqualPKvS0_"; // Boolean __attribute__((overloadable)) __HIShapeEqual(void const*, void const*)
	HIShapeEqual = (HIShapeEqualFunc) FindSymbol(img, mangled_name);
    }
    return HIShapeEqual(srca, srcb);
}