Cheng Shao pushed to branch wip/validate-fix-werror at Glasgow Haskell Compiler / GHC Commits: e34cb6da by Adam Gundry at 2026-03-20T12:20:00-04:00 ghci: Mention active language edition in startup banner Per GHC proposal 632, this makes the GHCi startup banner include the active language edition, plus an indication of whether this was the default (as opposed to being explicitly selected via an option such as `-XGHC2024`). For example: ``` $ ghci GHCi, version 9.14.1: https://www.haskell.org/ghc/ :? for help Using default language edition: GHC2024 ghci> ``` Fixes #26037. - - - - - 52c3e6ba by sheaf at 2026-03-20T12:21:09-04:00 Improve incomplete record selector warnings This commit stops GHC from emitting spurious incomplete record selector warnings for bare selectors/projections such as .fld There are two places we currently emit incomplete record selector warnings: 1. In the desugarer, when we see a record selector or an occurrence of 'getField'. Here, we can use pattern matching information to ensure we don't give false positives. 2. In the typechecker, which might sometimes give false positives but can emit warnings in cases that the pattern match checker would otherwise miss. This is explained in Note [Detecting incomplete record selectors] in GHC.HsToCore.Pmc. Now, we obviously don't want to emit the same error twice, and generally we prefer (1), as those messages contain fewer false positives. So we suppress (2) when we are sure we are going to emit (1); the logic for doing so is in GHC.Tc.Instance.Class.warnIncompleteRecSel, and works by looking at the CtOrigin. Now, the issue was that this logic handled explicit record selectors as well as overloaded record field selectors such as "x.r" (which turns into a simple GetFieldOrigin CtOrigin), but it didn't properly handle record projectors like ".fld" or ".fld1.fld2" (which result in other CtOrigins such as 'RecordFieldProjectionOrigin'). To solve this problem, we re-use the 'isHasFieldOrigin' introduced in fbdc623a (slightly adjusted). On the way, we also had to update the desugarer with special handling for the 'ExpandedThingTc' case in 'ds_app', to make sure that 'ds_app_var' sees all the type arguments to 'getField' in order for it to indeed emit warnings like in (1). Fixes #26686 - - - - - 309d7e87 by Cheng Shao at 2026-03-20T12:21:53-04:00 rts: opportunistically grow the MutableByteArray# in-place in resizeMutableByteArray# Following !15234, this patch improves `resizeMutableByteArray#` memory efficiency by growing the `MutableByteArray#` in-place if possible, addressing an old todo comment here. Also adds a new test case `resizeMutableByteArrayInPlace` that stresses this behavior. - - - - - 7d4ef162 by Matthew Craven at 2026-03-20T12:22:47-04:00 Change representation of floating point literals This commit changes the representation of floating point literals throughough the compiler, in particular in Core and Cmm. The Rational type is deficient for this purpose, dealing poorly with NaN, +/-Infinity, and negative zero. Instead, the new module GHC.Types.Literal.Floating uses the host Float/Double type to represent NaNs, infinities and negative zero. It also contains a Rational constructor, for the benefit of -fexcess-precision. Other changes: - Remove Note [negative zero] and related code This also removes the restrictions on constant-folding of division by zero, and should make any problems with NaN/Infinity more obvious. - Use -0.0 as the additive identity for Core constant folding rules for floating-point addition, fixing #21227. - Manual worker-wrapper for GHC.Float.rationalToDouble. This is intended to prevent the compiler's WW on this function from interfering with constant-folding. This change means that we now avoid allocating a box for the result of a 'realToFrac' call in T10359. - Combine floatDecodeOp and doubleDecodeOp. This change also fixes a bug in doubleDecodeOp wherein it would incorrectly produce an Int# instead of an Int64# literal for the mantissa component with 64-bit targets. - Use Float/Double for assembly immediates, and update the X86 and PowerPC backends to properly handle special values such as NaN and infinity. - Allow 'rational_to' to handle zero denominators, fixing a TODO in GHC.Core.Opt.ConstantFold. Fixes #8364 #9811 #18897 #21227 Progress towards #26919 Metric Decrease: T10359 Co-authored-by: sheaf <sam.derbyshire@gmail.com> ------------------------- Metric Decrease: T1969 T5321FD ------------------------- - - - - - 80e2dd4f by Zubin Duggal at 2026-03-20T12:23:33-04:00 compiler/ffi: Collapse void pointer chains in capi wrappers New gcc/clang treat -Wincompatible-pointer-types as an error by default. Since C only allows implicit conversion from void*, not void**, capi wrappers for functions taking e.g. abstract** would fail to compile when the Haskell type Ptr (Ptr Abstract) was naively translated to void**. Collapse nested void pointers to a single void* when the pointee type has no known C representation. Fixes #26852 - - - - - 1c50bd7b by Luite Stegeman at 2026-03-20T12:24:37-04:00 Move some functions related to pointer tagging to a separate module - - - - - bfd7aafd by Luite Stegeman at 2026-03-20T12:24:37-04:00 Branchless unpacking for enumeration types Change unpacking for enumeration types to go to Word8#/Word16#/Word# directly instead of going through an intermediate unboxed sum. This allows us to do a branchless conversion using DataToTag and TagToEnum. Fixes #26970 - - - - - 72b20fc0 by Luite Stegeman at 2026-03-20T12:25:30-04:00 bytecode: Carefully SLIDE off the end of a stack chunk The SLIDE bytecode instruction was not checking for stack chunk boundaries and could corrupt the stack underflow frame, leading to crashes. We add a check to use safe writes if we cross the chunk boundary and also handle stack underflow if Sp is advanced past the underflow frame. fix #27001 - - - - - 2e22b43c by Cheng Shao at 2026-03-20T12:26:14-04:00 ghci: serialize BCOByteArray buffer directly when possible This patch changes the `Binary` instances of `BCOByteArray` to directly serialize the underlying buffer when possible, while also taking into account the issue of host-dependent `Word` width. See added comments and amended `Note [BCOByteArray serialization]` for detailed explanation. Closes #27020. - - - - - 89d9ba37 by Sylvain Henry at 2026-03-20T12:27:34-04:00 JS: replace BigInt with Number arithmetic for 32/64-bit quot/rem (#23597) Replace BigInt-based implementations of quotWord32, remWord32, quotRemWord32, quotRem2Word32, quotWord64, remWord64, quotInt64, and remInt64 with pure Number (double/integer) arithmetic to avoid the overhead of BigInt promotion. - - - - - ae4ddd60 by Sylvain Henry at 2026-03-20T12:28:28-04:00 Core: add constant-folding rules for Addr# eq/ne (#18032) - - - - - 3e767f98 by Matthew Pickering at 2026-03-20T12:29:11-04:00 Use OsPath rather than FilePath in Downsweep cache This gets us one step closure to uniformly using `OsPath` in the compiler. - - - - - 2c57de29 by Cheng Shao at 2026-03-20T12:29:55-04:00 hadrian: fix ghc-in-ghci flavour stage0 shared libraries This patch fixes missing stage0 shared libraries in hadrian ghc-in-ghci flavour, which was accidentally dropped in 669d09f950a6e88b903d9fd8a7571531774d4d5d and resulted in a regression in HLS support on linux/macos. Fixes #27057. - - - - - 5b1be555 by Sylvain Henry at 2026-03-20T12:30:48-04:00 JS: install rts/Types.h header file (#27033) It was an omission, making HsFFI.h not usable with GHC using the JS backend. - - - - - b883f08f by Cheng Shao at 2026-03-20T12:31:33-04:00 hadrian: don't compile RTS with -Winline This patch removes `-Winline` from cflags when compiling the RTS, given that: 1. It generates a huge pile of spam and hurts developer experience 2. Whether inlining happens is highly dependent on toolchains, flavours, etc, and it's not really an issue to fix if inlining doesn't happen; it's a hint to the C compiler anyway. Fixes #27060. - - - - - 333387d6 by Cheng Shao at 2026-03-20T12:31:33-04:00 hadrian: compile libffi-clib with -Wno-deprecated-declarations This patch adds `-Wno-deprecated-declarations` to cflags of `libffi-clib`, given that it produces noise at compile-time that aren't really our issue to fix anyway, it's from vendored libffi source code. - - - - - 67c47771 by Rodrigo Mesquita at 2026-03-20T12:32:17-04:00 Expose decodeStackWithIpe from ghc-experimental This decoding is useful to the debugger and it wasn't originally exported as an oversight. - - - - - 0cb532cd by Cheng Shao at 2026-03-20T20:02:36+00:00 rts: fix -Wcompare-distinct-pointer-types errors This commit fixes `-Wcompare-distinct-pointer-types` errors in the RTS which should have been caught by the `validate` flavour but was warnings in CI due to the recent `+werror` regression. - - - - - af543550 by Cheng Shao at 2026-03-20T20:02:36+00:00 ghc-internal: fix unused imports This commit fixes unused imports in `ghc-internal` which should have been caught by the `validate` flavour but was warnings in CI due to the recent `+werror` regression. Fixes #27059. - - - - - f14f93c8 by Cheng Shao at 2026-03-20T20:02:36+00:00 compiler: fix unused imports in GHC.Tc.Types.Origin This commit fixes unused imports in `GHC.Tc.Types.Origin` which should have been caught by the `validate` flavour but was warnings in CI due to the recent `+werror` regression. Fixes #27059. - - - - - 13268343 by Cheng Shao at 2026-03-20T20:02:36+00:00 hadrian: fix missing +werror in validate flavour This patch fixes missing `+werror` in validate flavour, which was an oversight in bb3a2ba1eefadf0b2ef4f39b31337a23eec67f29. Fixes #27066. - - - - - 108 changed files: - compiler/GHC/Builtin/Names.hs - compiler/GHC/ByteCode/Asm.hs - compiler/GHC/Cmm/CommonBlockElim.hs - compiler/GHC/Cmm/Expr.hs - compiler/GHC/Cmm/Opt.hs - compiler/GHC/Cmm/Parser.y - compiler/GHC/Cmm/Type.hs - compiler/GHC/Cmm/Utils.hs - compiler/GHC/CmmToAsm/AArch64/CodeGen.hs - compiler/GHC/CmmToAsm/AArch64/Ppr.hs - compiler/GHC/CmmToAsm/AArch64/Regs.hs - compiler/GHC/CmmToAsm/LA64/CodeGen.hs - compiler/GHC/CmmToAsm/LA64/Ppr.hs - compiler/GHC/CmmToAsm/LA64/Regs.hs - compiler/GHC/CmmToAsm/PPC/CodeGen.hs - compiler/GHC/CmmToAsm/PPC/Ppr.hs - compiler/GHC/CmmToAsm/PPC/Regs.hs - compiler/GHC/CmmToAsm/RV64/CodeGen.hs - compiler/GHC/CmmToAsm/RV64/Ppr.hs - compiler/GHC/CmmToAsm/RV64/Regs.hs - compiler/GHC/CmmToAsm/Wasm/FromCmm.hs - compiler/GHC/CmmToAsm/X86/CodeGen.hs - compiler/GHC/CmmToAsm/X86/Ppr.hs - compiler/GHC/CmmToAsm/X86/Regs.hs - compiler/GHC/CmmToC.hs - compiler/GHC/CmmToLlvm/CodeGen.hs - compiler/GHC/CmmToLlvm/Data.hs - compiler/GHC/Core.hs - compiler/GHC/Core/Make.hs - compiler/GHC/Core/Opt/ConstantFold.hs - compiler/GHC/Driver/Downsweep.hs - compiler/GHC/HsToCore/Expr.hs - compiler/GHC/HsToCore/Foreign/C.hs - compiler/GHC/HsToCore/Match/Literal.hs - compiler/GHC/HsToCore/Pmc.hs - compiler/GHC/HsToCore/Pmc/Solver/Types.hs - + compiler/GHC/Platform/Tag.hs - compiler/GHC/Stg/Unarise.hs - compiler/GHC/StgToByteCode.hs - compiler/GHC/StgToCmm/Closure.hs - compiler/GHC/StgToCmm/Expr.hs - compiler/GHC/StgToCmm/Lit.hs - compiler/GHC/StgToCmm/Prim.hs - compiler/GHC/StgToJS/Literal.hs - compiler/GHC/Tc/Errors.hs - compiler/GHC/Tc/Instance/Class.hs - compiler/GHC/Tc/TyCl/Build.hs - compiler/GHC/Tc/Types/Origin.hs - compiler/GHC/Types/Id/Make.hs - compiler/GHC/Types/Literal.hs - + compiler/GHC/Types/Literal/Floating.hs - compiler/GHC/Types/RepType.hs - compiler/GHC/Utils/Binary.hs - compiler/ghc.cabal.in - docs/users_guide/9.16.1-notes.rst - ghc/GHCi/UI.hs - ghc/Main.hs - hadrian/src/Settings/Flavours/GhcInGhci.hs - hadrian/src/Settings/Flavours/Validate.hs - hadrian/src/Settings/Packages.hs - libraries/ghc-experimental/ghc-experimental.cabal.in - + libraries/ghc-experimental/src/GHC/Stack/Decode/Experimental.hs - libraries/ghc-internal/src/GHC/Internal/Conc/IO.hs - libraries/ghc-internal/src/GHC/Internal/Event/Control.hs - libraries/ghc-internal/src/GHC/Internal/Float.hs - libraries/ghc-internal/src/GHC/Internal/RTS/Flags.hsc - libraries/ghc-internal/src/GHC/Internal/RTS/Flags/Test.hsc - libraries/ghc-internal/src/GHC/Internal/System/Posix/Internals.hs - libraries/ghc-internal/src/GHC/Internal/TopHandler.hs - libraries/ghci/GHCi/ResolvedBCO.hs - rts/Interpreter.c - rts/PrimOps.cmm - rts/js/arith.js - rts/rts.cabal - + testsuite/tests/bytecode/T27001.hs - + testsuite/tests/bytecode/T27001.stdout - testsuite/tests/bytecode/all.T - + testsuite/tests/codeGen/should_run/T21227.hs - + testsuite/tests/codeGen/should_run/T21227.stdout - + testsuite/tests/codeGen/should_run/T9811.hs - + testsuite/tests/codeGen/should_run/T9811.stdout - testsuite/tests/codeGen/should_run/all.T - testsuite/tests/count-deps/CountDepsAst.stdout - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/ffi/should_compile/T26852.h - + testsuite/tests/ffi/should_compile/T26852.hs - + testsuite/tests/ffi/should_compile/T26852.stderr - testsuite/tests/ffi/should_compile/all.T - testsuite/tests/ghci/should_run/BinaryArray.hs - testsuite/tests/interface-stability/ghc-experimental-exports.stdout - testsuite/tests/interface-stability/ghc-experimental-exports.stdout-mingw32 - + testsuite/tests/javascript/js-c-sources/T27033.hs - + testsuite/tests/javascript/js-c-sources/T27033.stdout - + testsuite/tests/javascript/js-c-sources/T27033_c.c - + testsuite/tests/javascript/js-c-sources/T27033_js.js - testsuite/tests/javascript/js-c-sources/all.T - testsuite/tests/numeric/should_run/T7014.hs - + testsuite/tests/overloadedrecflds/should_compile/T26686.hs - + testsuite/tests/overloadedrecflds/should_compile/T26686.stderr - testsuite/tests/overloadedrecflds/should_compile/all.T - testsuite/tests/rts/all.T - + testsuite/tests/rts/resizeMutableByteArrayInPlace.hs - + testsuite/tests/simplCore/should_compile/T18032.hs - + testsuite/tests/simplCore/should_compile/T18032.stderr - testsuite/tests/simplCore/should_compile/all.T - testsuite/tests/simplStg/should_run/all.T - + testsuite/tests/simplStg/should_run/unpack_enum.hs - + testsuite/tests/simplStg/should_run/unpack_enum.stdout The diff was not included because it is too large. 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