Fix Windows desktop OS build version reporting

lib/pal/desktop/WindowsDesktopSystemInformationImpl.cpp

@@ -29,6 +29,7 @@
 
 #include "WindowsEnvironmentInfo.hpp"
 
+#include <cstdint>
 #include <string>
 
 // This define is only available for TH1+
@@ -139,17 +140,44 @@ namespace PAL_NS_BEGIN {
             std::to_string(static_cast<int>(LOWORD(pffi->dwProductVersionLS)));
     }
 
-    /**
-     * Get OS BuildLabEx string
-     */
-    std::string getOsBuildLabEx()
+    const PCSTR c_currentVersion_Key = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
+
+    bool getCurrentVersionDwordValue(PCSTR valueName, uint32_t& value)
     {
-        char buff[MAX_PATH] = { 0 };
-        const PCSTR c_currentVersion_Key = "SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion";
-        const PCSTR c_buildLabEx_ValueName = "BuildLabEx";
-        DWORD size = sizeof(buff);
-        RegGetValueA(HKEY_LOCAL_MACHINE, c_currentVersion_Key, c_buildLabEx_ValueName, RRF_RT_REG_SZ | RRF_SUBKEY_WOW6464KEY, NULL, (char*)buff, &size);
-        return buff;
+        DWORD regValue = 0;
+        DWORD size = sizeof(regValue);
+        if (RegGetValueA(
+            HKEY_LOCAL_MACHINE,
+            c_currentVersion_Key,
+            valueName,
+            RRF_RT_REG_DWORD | RRF_SUBKEY_WOW6464KEY,
+            NULL,
+            &regValue,
+            &size) != ERROR_SUCCESS)
+        {
+            return false;
+        }
+
+        value = regValue;
+        return true;
+    }
+
+    std::string formatWindowsOsFullVersion(
+        unsigned long majorVersion,
+        unsigned long minorVersion,
+        unsigned long buildNumber,
+        uint32_t updateBuildRevision,
+        bool hasUpdateBuildRevision)
+    {
+        std::string version = std::to_string(majorVersion) + "." +
+                              std::to_string(minorVersion) + "." +
+                              std::to_string(static_cast<long long>(buildNumber));
+        if (hasUpdateBuildRevision)
+        {
+            version += "." + std::to_string(updateBuildRevision);
+        }
+
+        return version;
     }
 
     /**
@@ -175,8 +203,6 @@ namespace PAL_NS_BEGIN {
      */
     void getOsVersion(std::string& osMajorVersion, std::string& osFullVersion)
     {
-        std::string buildLabEx = getOsBuildLabEx();
-
         HMODULE hNtDll = ::GetModuleHandle(TEXT("ntdll.dll"));
         typedef HRESULT NTSTATUS;
         typedef NTSTATUS(__stdcall * RtlGetVersion_t)(PRTL_OSVERSIONINFOW);
@@ -186,8 +212,22 @@ namespace PAL_NS_BEGIN {
         if (pRtlGetVersion && SUCCEEDED(pRtlGetVersion(&rtlOsvi)))
         {
             osMajorVersion = std::to_string((long long)rtlOsvi.dwMajorVersion) + "." + std::to_string((long long)rtlOsvi.dwMinorVersion);
-            osFullVersion = osMajorVersion + "." + std::to_string((long long)rtlOsvi.dwBuildNumber);
-            osFullVersion = osMajorVersion + "." + buildLabEx;
+
+            // Use the kernel's authoritative dwBuildNumber from RtlGetVersion
+            // (see Windows team guidance on issue #1407). The registry
+            // CurrentBuildNumber / CurrentBuild values are only useful for
+            // offline reads of another Windows installation; for the running
+            // OS they are always in sync with the kernel build, so prefer the
+            // API. UBR is registry-only and is always safe to combine with the
+            // kernel build number.
+            uint32_t updateBuildRevision = 0;
+            bool hasUpdateBuildRevision = getCurrentVersionDwordValue("UBR", updateBuildRevision);
+            osFullVersion = formatWindowsOsFullVersion(
+                rtlOsvi.dwMajorVersion,
+                rtlOsvi.dwMinorVersion,
+                rtlOsvi.dwBuildNumber,
+                updateBuildRevision,
+                hasUpdateBuildRevision);
         }
     }
 

tests/unittests/PalTests.cpp

@@ -7,6 +7,9 @@
 #include "pal/PseudoRandomGenerator.hpp"
 #include "Version.hpp"
 
+#include <cstdint>
+#include <string>
+
 #ifdef HAVE_MAT_LOGGING
 #include "pal/PAL.hpp"
 #include <gtest/gtest.h>
@@ -24,6 +27,17 @@ using namespace PAL::detail;
 
 using namespace testing;
 
+#if defined(_WIN32) || defined(_WIN64)
+namespace PAL_NS_BEGIN {
+    std::string formatWindowsOsFullVersion(
+        unsigned long majorVersion,
+        unsigned long minorVersion,
+        unsigned long buildNumber,
+        uint32_t updateBuildRevision,
+        bool hasUpdateBuildRevision);
+} PAL_NS_END
+#endif
+
 class PalTests : public Test {};
 
 TEST_F(PalTests, UuidGeneration)
@@ -95,6 +109,29 @@ TEST_F(PalTests, FormatUtcTimestampMsAsISO8601)
     EXPECT_THAT(PAL::formatUtcTimestampMsAsISO8601(2147483647999ll), Eq("2038-01-19T03:14:07.999Z"));
 }
 
+#if defined(_WIN32) || defined(_WIN64)
+TEST_F(PalTests, WindowsOsFullVersionIncludesUbrWhenPresent)
+{
+    EXPECT_THAT(
+        PAL::formatWindowsOsFullVersion(10, 0, 26200, 1234, true),
+        Eq("10.0.26200.1234"));
+}
+
+TEST_F(PalTests, WindowsOsFullVersionOmitsUbrWhenMissing)
+{
+    EXPECT_THAT(
+        PAL::formatWindowsOsFullVersion(10, 0, 26200, 0, false),
+        Eq("10.0.26200"));
+}
+
+TEST_F(PalTests, WindowsOsFullVersionIncludesZeroUbrWhenPresent)
+{
+    EXPECT_THAT(
+        PAL::formatWindowsOsFullVersion(10, 0, 26200, 0, true),
+        Eq("10.0.26200.0"));
+}
+#endif
+
 TEST_F(PalTests, MonotonicTime)
 {
     int64_t t0 = PAL::getMonotonicTimeMs();