From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Avi Drissman <avi@chromium.org>
Date: Sat, 25 Jul 2020 17:38:19 +0000
Subject: Make macOS OS version numbers consistent

The "IsOS/IsAtLeastOS/IsAtMostOS" functions are driven from the Darwin
version number, which is always accurate. Adjust the
SysInfo::OperatingSystemVersionNumbers() function to return accurate
version numbers (or the best we can deduce) so that all version
numbers returned by helper functions are accurate and consistent.

Bug: 1101439
Bug: 1108832
Change-Id: I2ca92478d76bf572cc55875cba443f4978482d10
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2315490
Reviewed-by: Mark Mentovai <mark@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#791491}

diff --git a/base/system/sys_info_mac.mm b/base/system/sys_info_mac.mm
index 265d7678060fd003b4f28b2b50f8a80be5253c88..3becbd628e19084de6fd87de4adcdec2c5af67b4 100644
--- a/base/system/sys_info_mac.mm
+++ b/base/system/sys_info_mac.mm
@@ -62,6 +62,19 @@ void SysInfo::OperatingSystemVersionNumbers(int32_t* major_version,
   *major_version = version.majorVersion;
   *minor_version = version.minorVersion;
   *bugfix_version = version.patchVersion;
+
+  // TODO(https://crbug.com/1108832): If an app is built against a pre-macOS
+  // 11.0 SDK, macOS will lie as to what version it is, saying that it is macOS
+  // "10.16" rather than "11.0". The problem is that the "IsOS/IsAtLeastOS/
+  // IsAtMostOS" functions are driven from the Darwin version number, which
+  // isn't lied about, and therefore the values returned by this function and
+  // those functions are inconsistent. Therefore, unlie about these values.
+
+  if (*major_version == 10 && *minor_version >= 16) {
+    *major_version = *minor_version - 5;
+    *minor_version = *bugfix_version;
+    *bugfix_version = 0;
+  }
 }
 
 // static
