dSYM introspection in Swift on macOS.swift

import Foundation
import MachO.dyld
import MachO.getsect

extension DefaultStringInterpolation {
  mutating func appendInterpolation(pointer: Int) {
    appendInterpolation(String(format: "0x%016\(PRIxPTR)", pointer))
  }
}

enum CurrentExecutable {
  static let baseAddress = getsegbyname("__TEXT").pointee.vmaddr
  static let imageSlides = Dictionary(
    uniqueKeysWithValues:
      (0..<_dyld_image_count())
        .map { (String(cString: _dyld_get_image_name($0)), _dyld_get_image_vmaddr_slide($0)) })
  /// This is suboptimal
  static let name: String = {
    var requiredSize: UInt32 = 0
    /**
     -1 indicates the path didn't fit, which is expected given that we provided a buffer of size 0. As a side effect, this sets `requiredSize` to the size of buffer we require.
     */
    precondition(_NSGetExecutablePath(nil, &requiredSize) == -1)
    return String(
      unsafeUninitializedCapacity: Int(requiredSize),
      initializingUTF8With: { buffer in
        buffer.withMemoryRebound(to: Int8.self) { buffer in
          precondition(_NSGetExecutablePath(buffer.baseAddress, &requiredSize) == 0)
          /// We do not include the NULL terminator
          return Int(requiredSize) - 1
        }
      })
  }()
  static let imageSlide = imageSlides[name]!
}

func printBacktrace() {
  Thread.callStackReturnAddresses.map(\.intValue).forEach { returnAddress in
    let symbolAddress = returnAddress - CurrentExecutable.imageSlide
    print("""
      \(pointer: returnAddress): \(pointer: symbolAddress)
      """)
  }
}

/* */ printBacktrace()
  
// Debug info can be accessed using a dSYM like so: dwarfdump <path-to-dSYM> --lookup=<symbolAddress>