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termux-packages/packages/ghc/cabal-set-default-prefix.patch
Aditya Alok e21578f662 bump(main/ghc): 9.12.2
Patched `rts` heap reservation logic on Android:

  * Need for patch

  - There seems to be a bug on Android. Sometimes simple commands like `ghc --help` usage 90% - 100% cpu and hangs.

  - It doesn't happen every time, but ~25% of the times (at least in my
    testing).

  * Cause of the bug

  - The function `osReserveHeapMemory` tries to allocate virtual space starting
    from `0x4200000000`. The allocated space has to start at an address >= this address.

  - If the kernel doesn't allocate inside this space, it keeps on repeating the
    `mmap` call with increasing starting point.

  - Now, on Android the kernel sometimes return an address above (as in counting)
    this `hint` address. It repeatedly returns the same address for subsequent calls.

  - Thus, an infinite loop occurs.

  References:
    - 383be28ffd/rts/posix/OSMem.c (L461)
    - https://github.com/termux/termux-packages/pull/22991#issuecomment-2759137291

  * Solution (proposed by Robert Kirkman):

  - It introduces a new helper function `osTryReserveHeapMemoryRecursive`.
    This transforms the heap reservation logic into a recursive one.

  - `osTryReserveHeapMemory()` is run multiple times without unmapping the
    undesired addresses. Thus, forcing the kernel to map subsequent calls of
    `mmap` to a new, unique address until an address above the `0x4200000000`
    mark is obtained.

  - After which each recursive call unmaps its undesired address before returning
    the desired address (in order from last mapped to first mapped).

  References:
    - https://gitlab.haskell.org/ghc/ghc/-/merge_requests/14164
    - https://github.com/termux/termux-packages/pull/22991#issuecomment-2761325484

Co-authored-by: Robert Kirkman <rkirkman@termux.dev>
Signed-off-by: Aditya Alok <alok@termux.dev>
2025-04-08 18:17:01 +02:00

12 lines
570 B
Diff

--- ghc-9.12.1/libraries/Cabal/Cabal/src/Distribution/Simple/InstallDirs.hs 2024-12-16 01:00:10.000000000 +0530
+++ ghc-9.12.1.mod/libraries/Cabal/Cabal/src/Distribution/Simple/InstallDirs.hs 2025-01-04 20:05:06.846734461 +0530
@@ -205,7 +205,7 @@
windowsProgramFilesDir <- getWindowsProgramFilesDir
return (windowsProgramFilesDir </> "Haskell")
Haiku -> return "/boot/system/non-packaged"
- _ -> return "/usr/local"
+ _ -> return "@TERMUX_PREFIX@"
installLibDir <-
case buildOS of
Windows -> return "$prefix"