Fix the dsymutil heuristic for excluding system interfaces. (llvm#93745)

The function was meant to find the Developer/ dir, but it found a
Developer directory nested deep inside the top-level Developer dir.

The new implementation rejects everything in Xcode.app/Developer in
broad strokes.

rdar: //128571037
Change-Id: Ieab957577601374237eea95dd07db01c131912d8

Author: adrian-prantl

llvm/include/llvm/DWARFLinker/Utils.h

@@ -36,17 +36,42 @@ inline Error finiteLoop(function_ref<Expected<bool>()> Iteration,
   return createStringError(std::errc::invalid_argument, "Infinite recursion");
 }
 
+/// Make a best effort to guess the
 /// Xcode.app/Contents/Developer path from an SDK path.
 inline StringRef guessDeveloperDir(StringRef SysRoot) {
-  // Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
   SmallString<128> Result;
-  StringRef Base = sys::path::parent_path(SysRoot);
-  if (sys::path::filename(Base) != "SDKs")
-    return Result;
-  Base = sys::path::parent_path(Base);
-  Result = Base;
-  Result += "/Toolchains";
-  return Result;
+  // Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk
+  auto it = sys::path::rbegin(SysRoot);
+  auto end = sys::path::rend(SysRoot);
+  if (it == end || !it->ends_with(".sdk"))
+    return {};
+  ++it;
+  // Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs
+  if (it == end || *it != "SDKs")
+    return {};
+  auto developerEnd = it;
+  ++it;
+  while (it != end) {
+    // Contents/Developer/Platforms/MacOSX.platform/Developer
+    if (*it != "Developer")
+      return {};
+    ++it;
+    if (it == end)
+      return {};
+    if (*it == "Contents")
+      return StringRef(SysRoot.data(),
+                       developerEnd - sys::path::rend(SysRoot) - 1);
+    // Contents/Developer/Platforms/MacOSX.platform
+    if (!it->ends_with(".platform"))
+      return {};
+    ++it;
+    // Contents/Developer/Platforms
+    if (it == end || *it != "Platforms")
+      return {};
+    developerEnd = it;
+    ++it;
+  }
+  return {};
 }
 
 /// Make a best effort to determine whether Path is inside a toolchain.

llvm/unittests/DWARFLinkerParallel/DWARFLinkerTest.cpp

@@ -5,3 +5,25 @@
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
+
+#include "llvm/DWARFLinker/Utils.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+using namespace dwarf_linker;
+
+#define DEVELOPER_DIR "/Applications/Xcode.app/Contents/Developer"
+
+namespace {
+
+TEST(DWARFLinker, PathTest) {
+  EXPECT_EQ(guessDeveloperDir("/Foo"), "");
+  EXPECT_EQ(guessDeveloperDir("Foo.sdk"), "");
+  EXPECT_EQ(guessDeveloperDir(
+                DEVELOPER_DIR
+                "/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.4.sdk"),
+            DEVELOPER_DIR);
+  EXPECT_EQ(guessDeveloperDir(DEVELOPER_DIR "/SDKs/MacOSX.sdk"), DEVELOPER_DIR);
+}
+
+} // anonymous namespace