diff options
Diffstat (limited to 'compiler/GHC/Driver')
| -rw-r--r-- | compiler/GHC/Driver/Pipeline.hs | 68 | ||||
| -rw-r--r-- | compiler/GHC/Driver/Session.hs | 38 |
2 files changed, 98 insertions, 8 deletions
diff --git a/compiler/GHC/Driver/Pipeline.hs b/compiler/GHC/Driver/Pipeline.hs index 8386dd9c7e..7276762f0f 100644 --- a/compiler/GHC/Driver/Pipeline.hs +++ b/compiler/GHC/Driver/Pipeline.hs @@ -394,7 +394,56 @@ compileEmptyStub dflags hsc_env basename location mod_name = do -- --------------------------------------------------------------------------- -- Link - +-- +-- Note [Dynamic linking on macOS] +-- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-- +-- Since macOS Sierra (10.14), the dynamic system linker enforces +-- a limit on the Load Commands. Specifically the Load Command Size +-- Limit is at 32K (32768). The Load Commands contain the install +-- name, dependencies, runpaths, and a few other commands. We however +-- only have control over the install name, dependencies and runpaths. +-- +-- The install name is the name by which this library will be +-- referenced. This is such that we do not need to bake in the full +-- absolute location of the library, and can move the library around. +-- +-- The dependency commands contain the install names from of referenced +-- libraries. Thus if a libraries install name is @rpath/libHS...dylib, +-- that will end up as the dependency. +-- +-- Finally we have the runpaths, which informs the linker about the +-- directories to search for the referenced dependencies. +-- +-- The system linker can do recursive linking, however using only the +-- direct dependencies conflicts with ghc's ability to inline across +-- packages, and as such would end up with unresolved symbols. +-- +-- Thus we will pass the full dependency closure to the linker, and then +-- ask the linker to remove any unused dynamic libraries (-dead_strip_dylibs). +-- +-- We still need to add the relevant runpaths, for the dynamic linker to +-- lookup the referenced libraries though. The linker (ld64) does not +-- have any option to dead strip runpaths; which makes sense as runpaths +-- can be used for dependencies of dependencies as well. +-- +-- The solution we then take in GHC is to not pass any runpaths to the +-- linker at link time, but inject them after the linking. For this to +-- work we'll need to ask the linker to create enough space in the header +-- to add more runpaths after the linking (-headerpad 8000). +-- +-- After the library has been linked by $LD (usually ld64), we will use +-- otool to inspect the libraries left over after dead stripping, compute +-- the relevant runpaths, and inject them into the linked product using +-- the install_name_tool command. +-- +-- This strategy should produce the smallest possible set of load commands +-- while still retaining some form of relocatability via runpaths. +-- +-- The only way I can see to reduce the load command size further would be +-- by shortening the library names, or start putting libraries into the same +-- folders, such that one runpath would be sufficient for multiple/all +-- libraries. link :: GhcLink -- interactive or batch -> DynFlags -- dynamic flags -> Bool -- attempt linking in batch mode? @@ -1787,9 +1836,12 @@ linkBinary' staticLink dflags o_files dep_units = do rc_objs <- maybeCreateManifest dflags output_fn - let link = if staticLink - then GHC.SysTools.runLibtool - else GHC.SysTools.runLink + let link dflags args | staticLink = GHC.SysTools.runLibtool dflags args + | platformOS platform == OSDarwin + = GHC.SysTools.runLink dflags args >> GHC.SysTools.runInjectRPaths dflags pkg_lib_paths output_fn + | otherwise + = GHC.SysTools.runLink dflags args + link dflags ( map GHC.SysTools.Option verbFlags ++ [ GHC.SysTools.Option "-o" @@ -1856,7 +1908,13 @@ linkBinary' staticLink dflags o_files dep_units = do ++ pkg_link_opts ++ pkg_framework_opts ++ (if platformOS platform == OSDarwin - then [ "-Wl,-dead_strip_dylibs" ] + -- dead_strip_dylibs, will remove unused dylibs, and thus save + -- space in the load commands. The -headerpad is necessary so + -- that we can inject more @rpath's later for the left over + -- libraries during runInjectRpaths phase. + -- + -- See Note [Dynamic linking on macOS]. + then [ "-Wl,-dead_strip_dylibs", "-Wl,-headerpad,8000" ] else []) )) diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs index 041c7bc418..a0c2331d53 100644 --- a/compiler/GHC/Driver/Session.hs +++ b/compiler/GHC/Driver/Session.hs @@ -145,8 +145,8 @@ module GHC.Driver.Session ( versionedAppDir, versionedFilePath, extraGccViaCFlags, globalPackageDatabasePath, pgm_L, pgm_P, pgm_F, pgm_c, pgm_a, pgm_l, pgm_lm, pgm_dll, pgm_T, - pgm_windres, pgm_libtool, pgm_ar, pgm_ranlib, pgm_lo, pgm_lc, - pgm_lcc, pgm_i, + pgm_windres, pgm_libtool, pgm_ar, pgm_otool, pgm_install_name_tool, + pgm_ranlib, pgm_lo, pgm_lc, pgm_lcc, pgm_i, opt_L, opt_P, opt_F, opt_c, opt_cxx, opt_a, opt_l, opt_lm, opt_i, opt_P_signature, opt_windres, opt_lo, opt_lc, opt_lcc, @@ -885,6 +885,10 @@ pgm_lcc :: DynFlags -> (String,[Option]) pgm_lcc dflags = toolSettings_pgm_lcc $ toolSettings dflags pgm_ar :: DynFlags -> String pgm_ar dflags = toolSettings_pgm_ar $ toolSettings dflags +pgm_otool :: DynFlags -> String +pgm_otool dflags = toolSettings_pgm_otool $ toolSettings dflags +pgm_install_name_tool :: DynFlags -> String +pgm_install_name_tool dflags = toolSettings_pgm_install_name_tool $ toolSettings dflags pgm_ranlib :: DynFlags -> String pgm_ranlib dflags = toolSettings_pgm_ranlib $ toolSettings dflags pgm_lo :: DynFlags -> (String,[Option]) @@ -2267,6 +2271,10 @@ dynamic_flags_deps = [ $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_libtool = f } , make_ord_flag defFlag "pgmar" $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_ar = f } + , make_ord_flag defFlag "pgmotool" + $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_otool = f} + , make_ord_flag defFlag "pgminstall_name_tool" + $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_install_name_tool = f} , make_ord_flag defFlag "pgmranlib" $ hasArg $ \f -> alterToolSettings $ \s -> s { toolSettings_pgm_ranlib = f } @@ -3780,7 +3788,6 @@ defaultFlags settings Opt_OmitYields, Opt_PrintBindContents, Opt_ProfCountEntries, - Opt_RPath, Opt_SharedImplib, Opt_SimplPreInlining, Opt_VersionMacros @@ -3791,6 +3798,8 @@ defaultFlags settings ++ default_PIC platform + ++ default_RPath platform + ++ concatMap (wayGeneralFlags platform) (defaultWays settings) ++ validHoleFitDefaults @@ -3831,6 +3840,29 @@ default_PIC platform = -- information. _ -> [] + +-- We usually want to use RPath, except on macOS (OSDarwin). On recent macOS +-- versions the number of load commands we can embed in a dynamic library is +-- restricted. Hence since b592bd98ff2 we rely on -dead_strip_dylib to only +-- link the needed dylibs instead of linking the full dependency closure. +-- +-- If we split the library linking into injecting -rpath and -l @rpath/... +-- components, we will reduce the number of libraries we link, however we will +-- still inject one -rpath entry for each library, independent of their use. +-- That is, we even inject -rpath values for libraries that we dead_strip in +-- the end. As such we can run afoul of the load command size limit simply +-- by polluting the load commands with RPATH entries. +-- +-- Thus, we disable Opt_RPath by default on OSDarwin. The savvy user can always +-- enable it with -use-rpath if they so wish. +-- +-- See Note [Dynamic linking on macOS] + +default_RPath :: Platform -> [GeneralFlag] +default_RPath platform | platformOS platform == OSDarwin = [] +default_RPath _ = [Opt_RPath] + + -- General flags that are switched on/off when other general flags are switched -- on impliedGFlags :: [(GeneralFlag, TurnOnFlag, GeneralFlag)] |