GHC's configure script detects MADV_FREE when it shouldn't
In osDecommitMemory there is a #define for MADV_FREE. The presence of MADV_FREE is detected by the configure script, however merely testing for the presence of this symbol does not prove that MADV_FREE is supported by the kernel (which was introduced in 4.5). On newer versions of GCC (e.g. 6.1.1 on Alpine Edge), MADV_FREE is included in the compiler's header files, thus leading to a false positive.
The impact of this bug is that when GHC is compiled with a more recent version of GCC, "unable to decommit memory: Invalid argument" errors will abound.