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In this patch we just define new CPP vars, but don't yet use them or replace the existing approach. That will follow. The intention here is that every I/O manager can be enabled/disabled at GHC build time (subject to some constraints). More than one I/O manager can be enabled to be built. At least one I/O manager supporting the non-threaded RTS must be enabled as well as at least one supporting the non-threaded RTS. The I/O managers enabled here will become the choices available at runtime at RTS startup (in later patches). The choice can be made with RTS flags. There are separate sets of choices for the threaded and non-threaded RTS ways, because most I/O managers are specific to these ways. Furthermore we must establish a default I/O manager for the threaded and non-threaded RTS. Most I/O managers are platform-specific so there are checks to ensure each one can be enabled on the platform. Such checks are also where (in future) any system dependencies (e.g. libraries) can be checked. The output is a set of CPP flags (in the mk/config.h file), with one flag per named I/O manager: * IOMGR_BUILD_<name> : which ones should be built (some) * IOMGR_DEFAULT_NON_THREADED_<name> : which one is default (exactly one) * IOMGR_DEFAULT_THREADED_<name> : which one is default (exactly one) and a set of derived flags in IOManager.h * IOMGR_ENABLED_<name> : enabled for the current RTS way Note that IOMGR_BUILD_<name> just says that an I/O manager will be built for _some_ RTS way (i.e. threaded or non-threaded). The derived flags IOMGR_ENABLED_<name> in IOManager.h say if each I/O manager is enabled in the "current" RTS way. These are the ones that can be used for conditional compilation of the I/O manager code. Co-authored-by:Pi Delport <pi@well-typed.com>
In this patch we just define new CPP vars, but don't yet use them or replace the existing approach. That will follow. The intention here is that every I/O manager can be enabled/disabled at GHC build time (subject to some constraints). More than one I/O manager can be enabled to be built. At least one I/O manager supporting the non-threaded RTS must be enabled as well as at least one supporting the non-threaded RTS. The I/O managers enabled here will become the choices available at runtime at RTS startup (in later patches). The choice can be made with RTS flags. There are separate sets of choices for the threaded and non-threaded RTS ways, because most I/O managers are specific to these ways. Furthermore we must establish a default I/O manager for the threaded and non-threaded RTS. Most I/O managers are platform-specific so there are checks to ensure each one can be enabled on the platform. Such checks are also where (in future) any system dependencies (e.g. libraries) can be checked. The output is a set of CPP flags (in the mk/config.h file), with one flag per named I/O manager: * IOMGR_BUILD_<name> : which ones should be built (some) * IOMGR_DEFAULT_NON_THREADED_<name> : which one is default (exactly one) * IOMGR_DEFAULT_THREADED_<name> : which one is default (exactly one) and a set of derived flags in IOManager.h * IOMGR_ENABLED_<name> : enabled for the current RTS way Note that IOMGR_BUILD_<name> just says that an I/O manager will be built for _some_ RTS way (i.e. threaded or non-threaded). The derived flags IOMGR_ENABLED_<name> in IOManager.h say if each I/O manager is enabled in the "current" RTS way. These are the ones that can be used for conditional compilation of the I/O manager code. Co-authored-by:
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