How to access properties/member of struct pointer in Swift

Question

I am messing around with Mach-O Headers and dyld and came across this function _dyld_get_image_header that returns a pointer to the mach header of a dynamic library.

I thought I might be able to access the Mach-O segments of dynamic libraries through this pointer following this article. However, I am not able to access the properties of the Mach-O Headers and am getting errors . In the Swift code below, I attempted to access the ncmds or load command property of the struct and was met with an error:

var currentLibrary = 0
// Gets Pointer to Mach Header of First Dynamic Library, Index 0
let libHeader = unsafeBitCast(_dyld_get_image_header(UInt32(currentLibrary)), to: UnsafePointer<mach_header_64>.self)

print(libHeader.ncmds)

Error:

Value of type 'UnsafePointer<mach_header_64>' has no member 'ncmds'

Possibly helpful: https://stackoverflow.com/q/39732016/1187415 — Martin R, Jan 27 '21 at 06:39

score 2 · Accepted Answer · answered Jan 27 '21 at 03:55

It's similar to c, where you would use the -> operator (libHeader->ncmds), requivalent to (*libHeader).ncmds. That is, first your reference the pointer to get to the mach_header_64 value, then you access its ncmds field.

In Swift, it's the exact same idea, with different syntax: libHeaver.pointee.ncmds

How to access properties/member of struct pointer in Swift

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