[pstl] Error out when the backend is left unspecified
Instead of silently falling back to the serial backend, it's better if
we fail loudly when the parallel backend is left unspecified. Since we
have a __pstl_config_site header, a backend should always be specified.
llvm-svn: 368285
GitOrigin-RevId: a8a436ef95908a560ddca8c5f7c5349d2dc2f977
diff --git a/include/pstl/internal/pstl_config.h b/include/pstl/internal/pstl_config.h
index ba0bc14..c2a737b 100644
--- a/include/pstl/internal/pstl_config.h
+++ b/include/pstl/internal/pstl_config.h
@@ -19,9 +19,7 @@
#define _PSTL_VERSION_PATCH (_PSTL_VERSION % 10)
#if !defined(_PSTL_PAR_BACKEND_SERIAL) && !defined(_PSTL_PAR_BACKEND_TBB)
-// TODO: In the future, we need to handle this setting using a configure-time
-// option and something like a __config_site header.
-# define _PSTL_PAR_BACKEND_SERIAL
+# error "A parallel backend must be specified"
#endif
// Check the user-defined macro for warnings
