Ordinal 342 is really named SHInterlockedCompareExchange.

dlls/shlwapi/ordinal.c

@@ -1793,7 +1793,7 @@ HICON WINAPI SHLWAPI_337(LPCWSTR lpszFile, INT nIconIndex, HICON *phiconLarge,
  *      @	[SHLWAPI.342]
  *
  */
-LONG WINAPI SHLWAPI_342( PLONG dest, LONG xchg, LONG compare)
+LONG WINAPI SHInterlockedCompareExchange( PLONG dest, LONG xchg, LONG compare)
 {
         return InterlockedCompareExchange(dest, xchg, compare);
 }

dlls/shlwapi/shlwapi.spec

@@ -351,7 +351,7 @@ debug_channels (shell)
 339 forward @ kernel32.GetNumberFormatW
 340 forward @ user32.MessageBoxW
 341 forward @ kernel32.FindNextFileW
-342 stdcall @(ptr long long) SHLWAPI_342
+342 stdcall @(ptr long long) SHInterlockedCompareExchange
 343 stub @
 344 stub @
 345 stub @