How to get dylib version information which are in a directory - objective-c

Question

I wanted to get the dylib version. I've a dylib path for which I wanted to get the version number.
I've tried "otool -L" command and it's giving me the proper output but as per the requirements I can't use it, since I've 100 of dylib in a directory for which I wanted to get the version information and I can't run "otool" command for each dylib through NSTask and NSPipe.
I've also found the NSVersionOfLinkTimeLibrary() function to get the dylib version, but as per the documentation NSVersionOfLinkTimeLibrary returns the version number for linked libraries and not for other dylib.
Any help on this would be helpful.
Thanks.
Omkar

Answer 1

I've solved it by writing my own dylib parser. Below is the code snippet
- (int64_t)getDylibVersion :(NSString *)dylibPth
{
const char* strFilePath = [dylibPth UTF8String];
FILE* fileHandle = fopen(strFilePath, "rb");
struct mach_header mh;
if(fileHandle)
{
size_t bytesRead = fread(&mh, 1, sizeof(mh), fileHandle);
if(bytesRead == sizeof(mh))
{
if((mh.magic == MH_MAGIC_64 || mh.magic == MH_MAGIC) && mh.filetype == MH_DYLIB)
{
for(int j = 0; j < mh.ncmds; j++)
{
union
{
struct load_command lc;
struct dylib_command dc;
} load_command;
if (sizeof(load_command.lc) != fread(&load_command.lc, 1, sizeof(load_command.lc), fileHandle))
goto fail;
switch (load_command.lc.cmd)
{
case LC_SEGMENT:
break;
case LC_UUID:
break;
case LC_DYLD_INFO_ONLY:
break;
case LC_SYMTAB:
break;
case LC_LOAD_DYLIB:
break;
case LC_ID_DYLIB:
{
if (sizeof(load_command) - sizeof(load_command.lc) != fread(&load_command.lc + 1, 1, sizeof(load_command) - sizeof(load_command.lc), dylib_handle))
goto fail;
fclose(fileHandle);
return(load_command.dc.dylib.current_version);
}
default:
break;
}
if (0 != fseek(fileHandle, load_command.lc.cmdsize - sizeof(load_command.lc), SEEK_CUR))
goto fail;
}
}
}
}
fail:
fclose(fileHandle);
return (-1);
}
Note that Mach-O dylib version numbers are encoded as 32-bit unsigned integers, with the major version in the high 16 bits, the minor version in bits 8 through 15, and the patch level in the low 8 bits:
uint32_t version = …;
uint32_t major = version >> 16;
uint32_t minor = (version >> 8) & 0xff;
uint32_t revision = version & 0xff;
Note also that the above code will only work for "thin" binaries. "Fat," multi-architecture binaries start with a fat header, which you'll need to negotiate first to find the slice for your desired architecture. Moreover, the above only works with architectures of the running architecture's endianness.

Answer 2

The way I see it, you have 2 options.
Load each dylib into your process and lookup the Mach-O headers on each, looking for the version numbers. The documentation should be complete and thorough enough to get you started.
Open each dylib as a normal file, and read and parse the Mach-O headers yourself. This avoid having to load each dylib into the process, but it does mean you need to then either parse the Mach-O binary format yourself, or find a library that can do it for you (I don't know of any off the top of my head).