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2025-11-13Replace off_t by pgoff_t in I/O routinesMichael Paquier
PostgreSQL's Windows port has never been able to handle files larger than 2GB due to the use of off_t for file offsets, only 32-bit on Windows. This causes signed integer overflow at exactly 2^31 bytes when trying to handle files larger than 2GB, for the routines touched by this commit. Note that large files are forbidden by ./configure (3c6248a828af) and meson (recent change, see 79cd66f28c65). This restriction also exists in v16 and older versions for the now-dead MSVC scripts. The code base already defines pgoff_t as __int64 (64-bit) on Windows for this purpose, and some function declarations in headers use it, but many internals still rely on off_t. This commit switches more routines to use pgoff_t, offering more portability, for areas mainly related to file extensions and storage. These are not critical for WAL segments yet, which have currently a maximum size allowed of 1GB (well, this opens the door at allowing a larger size for them). This matters more for segment files if we want to lift the large file restriction in ./configure and meson in the future, which would make sense to remove once/if all traces of off_t are gone from the tree. This can additionally matter for out-of-core code that may want files larger than 2GB in places where off_t is four bytes in size. Note that off_t is still used in other parts of the tree like buffile.c, WAL sender/receiver, base backup, pg_combinebackup, etc. These other code paths can be addressed separately, and their update will be required if we want to remove the large file restriction in the future. This commit is a good first cut in itself towards more portability, hopefully. On Unix-like systems, pgoff_t is defined as off_t, so this change only affects Windows behavior. Author: Bryan Green <dbryan.green@gmail.com> Reviewed-by: Thomas Munro <thomas.munro@gmail.com> Reviewed-by: Michael Paquier <michael@paquier.xyz> Discussion: https://postgr.es/m/0f238ff4-c442-42f5-adb8-01b762c94ca1@gmail.com
2025-01-01Update copyright for 2025Bruce Momjian
Backpatch-through: 13
2024-03-02Fix overflow in Windows replacement pg_pread/pg_pwrite.Thomas Munro
When calling the Windows file I/O APIs there is an implicit conversion from size_t to DWORD, which could overflow. Clamp the size at 1GB to avoid that. Not a really a live bug as we don't expect anything in PostgreSQL to call with such large values. Reviewed-by: Peter Eisentraut <peter@eisentraut.org> Discussion: https://postgr.es/m/1672202.1703441340%40sss.pgh.pa.us
2024-01-04Update copyright for 2024Bruce Momjian
Reported-by: Michael Paquier Discussion: https://postgr.es/m/ZZKTDPxBBMt3C0J9@paquier.xyz Backpatch-through: 12
2023-01-02Update copyright for 2023Bruce Momjian
Backpatch-through: 11
2022-09-29Restore pg_pread and friends.Thomas Munro
Commits cf112c12 and a0dc8271 were a little too hasty in getting rid of the pg_ prefixes where we use pread(), pwrite() and vectored variants. We dropped support for ancient Unixes where we needed to use lseek() to implement replacements for those, but it turns out that Windows also changes the current position even when you pass in an offset to ReadFile() and WriteFile() if the file handle is synchronous, despite its documentation saying otherwise. Switching to asynchronous file handles would fix that, but have other complications. For now let's just put back the pg_ prefix and add some comments to highlight the non-standard side-effect, which we can now describe as Windows-only. Reported-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Reviewed-by: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com> Discussion: https://postgr.es/m/20220923202439.GA1156054%40nathanxps13
2022-09-17Include c.h instead of postgres.h in src/port/*p{read,write}*.cAndres Freund
Frontend code shouldn't include postgres.h. Some files in src/port/ need to include postgres.h/postgres_fe.h, but these files don't. Discussion: https://postgr.es/m/20220915022626.5xx3ccgkzpkqw5mq@awork3.anarazel.de Backpatch: 12-, where 3fd2a7932ef introduced (some) of these files
2022-08-04Remove dead pread and pwrite replacement code.Thomas Munro
pread() and pwrite() are in SUSv2, and all targeted Unix systems have them. Previously, we defined pg_pread and pg_pwrite to emulate these function with lseek() on old Unixen. The names with a pg_ prefix were a reminder of a portability hazard: they might change the current file position. That hazard is gone, so we can drop the prefixes. Since the remaining replacement code is Windows-only, move it into src/port/win32p{read,write}.c, and move the declarations into src/include/port/win32_port.h. No need for vestigial HAVE_PREAD, HAVE_PWRITE macros as they were only used for declarations in port.h which have now moved into win32_port.h. Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us> Reviewed-by: Greg Stark <stark@mit.edu> Reviewed-by: Robert Haas <robertmhaas@gmail.com> Reviewed-by: Andres Freund <andres@anarazel.de> Discussion: https://postgr.es/m/CA+hUKGJ3LHeP9w5Fgzdr4G8AnEtJ=z=p6hGDEm4qYGEUX5B6fQ@mail.gmail.com