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Currently it is appearing on stderr, whereas the rest of the messages
from --make go to stdout, this change fixes that.

Rather than have main() be statically compiled as part of the RTS, we
now generate it into the tiny C file that we compile when linking a
binary.

The main motivation is that we want to pass the settings for the
-rtsotps and -with-rtsopts flags into the RTS, rather than relying on
fragile linking semantics to override the defaults, which don't work
with DLLs on Windows (#5373).  In order to do this, we need to extend
the API for initialising the RTS, so now we have:

void hs_init_ghc (int *argc, char **argv[],   // program arguments
                  RtsConfig rts_config);      // RTS configuration

hs_init_ghc() can optionally be used instead of hs_init(), and allows
passing in configuration options for the RTS.  RtsConfig is a struct,
which currently has two fields:

typedef struct {
    RtsOptsEnabledEnum rts_opts_enabled;
    const char *rts_opts;
} RtsConfig;

but might have more in the future.  There is a default value for the
struct, defaultRtsConfig, the idea being that you start with this and
override individual fields as necessary.

In fact, main() was in a separate static library, libHSrtsmain.a.
That's now gone.

Now that we always link in an extra object, we may as well always
define rtsOptsEnabled in it, rather than having a default value in
rts/hooks/RtsOptsEnabled.c.

Without it we get warnings like:
    ld: warning: could not create compact unwind for .LFB3: non-standard register 5 being saved in prolog

ld gives loads of warnings like:
    ld: warning: text reloc in _base_GHCziArr_unsafeArray_info to _base_GHCziArr_unsafeArray_closure
when linking any program. We're not sure whether this is something we
ought to fix, but for now we use the -Wl,-read_only_relocs,suppress flag
to silence them.

that it wasn't working on Alpha, because we had explicitly listed the
arches rather than having a sensible fallback).

Also refactor the check into one place.

Now that the in-tree gmp has been upgraded, it should no longer be
necessary, according to #5293.

- "-Wl,-no_pie" can be removed once GMP gets updated

being used.

We now track whether a module used any TH splices in the ModIface (and
at compile time in the TcGblEnv and ModGuts).  If a module used TH
splices last time it was compiled, then we ignore the results of the
normal recompilation check and recompile anyway, *unless* the module
is "stable" - that is, none of its dependencies (direct or indirect)
have changed.  The stability test is pretty important - otherwise ghc
--make would always recompile TH modules even if nothing at all had
changed, but it does require some extra plumbing to get this
information from GhcMake into HscMain.

test in driver/recomp009

"inplace/bin/ghc-stage1"   -H32m -O    -package-name base-4.4.0.0 -hide-all-packages -i -ilibraries/base/. -ilibraries/base/dist-install/build -ilibraries/base/dist-install/build/autogen -Ilibraries/base/dist-install/build -Ilibraries/base/dist-install/build/autogen -Ilibraries/base/include   -optP-DOPTIMISE_INTEGER_GCD_LCM -optP-include -optPlibraries/base/dist-install/build/autogen/cabal_macros.h -package ghc-prim-0.2.0.0 -package integer-gmp-0.3.0.0 -package rts-1.0 -split-objs -package-name base -XHaskell98 -XCPP -O2 -no-user-package-conf -rtsopts     -odir libraries/base/dist-install/build -hidir libraries/base/dist-install/build -stubdir libraries/base/dist-install/build -hisuf hi -osuf  o -hcsuf hc -c libraries/base/./GHC/Int.hs -o libraries/base/dist-install/build/GHC/Int.o
/usr/lib/gcc/sparc-unknown-linux-gnu/4.5.2/../../../../sparc-unknown-linux-gnu/bin/ld: --relax and -r may not be used together
collect2: ld returned 1 exit status
make[1]: *** [libraries/base/dist-install/build/GHC/Int.o] Error 1

Or with '-v' param:
/usr/bin/gcc -fno-stack-protector -nostdlib -nodefaultlibs -Wl,-r -Wl,--build-id=none -Wl,-x -o libraries/base/dist-install/build/GHC/Int.o /tmp/ghc45126_0/ghc45126_0.ldscript
/usr/lib/gcc/sparc-unknown-linux-gnu/4.5.2/../../../../sparc-unknown-linux-gnu/bin/ld: --relax and -r may not be used together

On SPARC gcc-4.5.2 has -mrelax in it's default specs, so we explicitly pass --no-relax
for ld to make sure gcc's default does not affect us.
Signed-off-by: Sergei Trofimovich <slyfox@gentoo.org>

kgardas authored Jun 13, 2011 and Simon Marlow committed Jun 27, 2011

It looks like where x86 assembly is using '@' character,
ARM assembly requires '%' character. This makes a problem in the patch
814edf44 'Force re-linking if
the options have changed (#4451)' which makes linking assembly
file uncompilable on ARM. This patch fixes this.

While we previously checked the safety of safe imported modules we
didn't do this check transitively. This can be a problem when we depend
on a trustworthy module in a package that is no longer trusted, so we
should fail compilation. We already stored in an interface file the
transitive list of packages a module depends on. Now we extend that list
to include a flag saying if we depend on that package being trusted as
well.

This patch disables the use of some GHC extensions in
Safe mode and also the use of certain flags. Some
are disabled completely while others are only allowed
on the command line and not in source PRAGMAS.

We also check that Safe imports are indeed importing
a Safe or Trustworthy module.

And remove cTargetOS/cTargetPlatform.

Instead of using the GNU As subsection feature on Linux/Windows
for TNTC we now use the LLVM Mangler on all platforms.

I've made cpp_args include gcc_args. It effectively didn't before,
but seeing as gcc_args sometimes has -D flags in, I think doing so
is the right thing to do.

Also a small refactoring in how the verbosity flag is handled.

otherwise some versions of gcc complain about a missing final newline.

Previously the code generator generated small code fragments labelled
with __stginit_M for each module M, and these performed whatever
initialisation was necessary for that module and recursively invoked
the initialisation functions for imported modules.  This appraoch had
drawbacks:

 - FFI users had to call hs_add_root() to ensure the correct
   initialisation routines were called.  This is a non-standard,
   and ugly, API.

 - unless we were using -split-objs, the __stginit dependencies would
   entail linking the whole transitive closure of modules imported,
   whether they were actually used or not.  In an extreme case (#4387,
   #4417), a module from GHC might be imported for use in Template
   Haskell or an annotation, and that would force the whole of GHC to
   be needlessly linked into the final executable.

So now instead we do our initialisation with C functions marked with
__attribute__((constructor)), which are automatically invoked at
program startup time (or DSO load-time).  The C initialisers are
emitted into the stub.c file.  This means that every time we compile
with -prof or -hpc, we now get a stub file, but thanks to #3687 that
is now invisible to the user.

There are some refactorings in the RTS (particularly for HPC) to
handle the fact that initialisers now get run earlier than they did
before.

The __stginit symbols are still generated, and the hs_add_root()
function still exists (but does nothing), for backwards compatibility.

This code has accumulated a great deal of cruft over the years, this
pass cleans up a lot of the surrounding cruft but leaves the actual
argument processing alone - so there's still more that could be done.

Bug fixed:

  - ghc_rts_opts should not be subject to the --rtsopts setting.  If
    the programmer explicitly declares options with ghc_rts_opts, they
    shouldn't also have to accept command-line RTS options to make them
    work.

A common sequence of commands (at least for me) is this:

$ ghc hello
1 of 1] Compiling Main             ( hello.hs, hello.o )
Linking hello ...
$ ./hello +RTS -s
hello: Most RTS options are disabled. Link with -rtsopts to enable them.
$ ghc hello -rtsopts
$

grr, nothing happened.  I could use -fforce-recomp, but if this was a
large program I probably don't want to recompile it all again, so:

$ rm hello
removed `hello'
$ ghc hello -rtsopts
Linking hello ...
$ ./hello +RTS -s
./hello +RTS -s
Hello World!
          51,264 bytes allocated in the heap
           2,904 bytes copied during GC
          43,808 bytes maximum residency (1 sample(s))
          17,632 bytes maximum slop
etc.

With this patch, GHC notices when the options have changed and forces
a relink, so you don't need to rm the binary or use -fforce-recomp.
This is done by adding the pertinent stuff to the binary in a special
section called ".debug-ghc-link-info":

$ readelf -p .debug-ghc-link-info ./hello
String dump of section 'ghc-linker-opts':
  [     0]  (["-lHSbase-4.3.1.0","-lHSinteger-gmp-0.2.0.2","-lgmp","-lHSghc-prim-0.2.0.0","-lHSrts","-lm","-lrt","-ldl","-u","ghczmprim_GHCziTypes_Izh_static_info","-u","ghczmprim_GHCziTypes_Czh_static_info","-u","ghczmprim_GHCziTypes_Fzh_static_info","-u","ghczmprim_GHCziTypes_Dzh_static_info","-u","base_GHCziPtr_Ptr_static_info","-u","base_GHCziWord_Wzh_static_info","-u","base_GHCziInt_I8zh_static_info","-u","base_GHCziInt_I16zh_static_info","-u","base_GHCziInt_I32zh_static_info","-u","base_GHCziInt_I64zh_static_info","-u","base_GHCziWord_W8zh_static_info","-u","base_GHCziWord_W16zh_static_info","-u","base_GHCziWord_W32zh_static_info","-u","base_GHCziWord_W64zh_static_info","-u","base_GHCziStable_StablePtr_static_info","-u","ghczmprim_GHCziTypes_Izh_con_info","-u","ghczmprim_GHCziTypes_Czh_con_info","-u","ghczmprim_GHCziTypes_Fzh_con_info","-u","ghczmprim_GHCziTypes_Dzh_con_info","-u","base_GHCziPtr_Ptr_con_info","-u","base_GHCziPtr_FunPtr_con_info","-u","base_GHCziStable_StablePtr_con_info","-u","ghczmprim_GHCziTypes_False_closure","-u","ghczmprim_GHCziTypes_True_closure","-u","base_GHCziPack_unpackCString_closure","-u","base_GHCziIOziException_stackOverflow_closure","-u","base_GHCziIOziException_heapOverflow_closure","-u","base_ControlziExceptionziBase_nonTermination_closure","-u","base_GHCziIOziException_blockedIndefinitelyOnMVar_closure","-u","base_GHCziIOziException_blockedIndefinitelyOnSTM_closure","-u","base_ControlziExceptionziBase_nestedAtomically_closure","-u","base_GHCziWeak_runFinalizzerBatch_closure","-u","base_GHCziTopHandler_runIO_closure","-u","base_GHCziTopHandler_runNonIO_closure","-u","base_GHCziConcziIO_ensureIOManagerIsRunning_closure","-u","base_GHCziConcziSync_runSparks_closure","-u","base_GHCziConcziSignal_runHandlers_closure","-lHSffi"],Nothing,RtsOptsAll,False,[],[])

And GHC itself uses the readelf command to extract it when deciding
whether to relink.  The reason for the name ".debug-ghc-link-info" is
that sections beginning with ".debug" are removed automatically by
strip.

This currently only works on Linux; Windows and OS X still have the
old behaviour.

to the way stub files were handled.