From: Tom Lane Date: Fri, 23 Sep 2016 14:09:52 +0000 (-0400) Subject: Don't trust CreateFileMapping() to clear the error code on success. X-Git-Tag: REL9_6_0~8 X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e7f5d8ea1c75cc341a966897760a812e437c4668;p=postgresql Don't trust CreateFileMapping() to clear the error code on success. We must test GetLastError() even when CreateFileMapping() returns a non-null handle. If that value were left over from some previous system call, we might be fooled into thinking the segment already existed. Experimentation on Windows 7 suggests that CreateFileMapping() clears the error code on success, but it is not documented to do so, so let's not rely on that happening in all Windows releases. Amit Kapila Discussion: <20811.1474390987@sss.pgh.pa.us> --- diff --git a/src/backend/storage/ipc/dsm_impl.c b/src/backend/storage/ipc/dsm_impl.c index 9cc9c5d2c2..8c706aee00 100644 --- a/src/backend/storage/ipc/dsm_impl.c +++ b/src/backend/storage/ipc/dsm_impl.c @@ -681,6 +681,9 @@ dsm_impl_windows(dsm_op op, dsm_handle handle, Size request_size, #endif size_low = (DWORD) request_size; + /* CreateFileMapping might not clear the error code on success */ + SetLastError(0); + hmap = CreateFileMapping(INVALID_HANDLE_VALUE, /* Use the pagefile */ NULL, /* Default security attrs */ PAGE_READWRITE, /* Memory is read/write */