Generate the C main() function when linking a binary (fixes #5373)

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.

1 files changed, 11 insertions, 8 deletions

diff --git a/rts/RtsMain.c b/rts/RtsMain.c
index a822da9749..0f6ca82382 100644
--- a/rts/RtsMain.c
+++ b/rts/RtsMain.c
@@ -13,7 +13,6 @@
 #include "RtsAPI.h"
 
 #include "RtsUtils.h"
-#include "RtsMain.h"
 #include "Prelude.h"
 #include "Task.h"
 #if defined(mingw32_HOST_OS)
@@ -33,8 +32,9 @@
 static int progargc;
 static char **progargv;
 static StgClosure *progmain_closure;  /* This will be ZCMain_main_closure */
+static RtsConfig rtsconfig;
 
-/* Hack: we assume that we're building a batch-mode system unless 
+/* Hack: we assume that we're building a batch-mode system unless
  * INTERPRETER is set
  */
 #ifndef INTERPRETER /* Hack */
@@ -43,9 +43,8 @@ static void real_main(void)
 {
     int exit_status;
     SchedulerStatus status;
-    /* all GranSim/GUM init is done in startupHaskell; sets IAmMainThread! */
 
-    startupHaskell(progargc,progargv,NULL);
+    hs_init_ghc(&progargc, &progargv, rtsconfig);
 
     /* kick off the computation by creating the main thread with a pointer
        to mainIO_closure representing the computation of the overall program;
@@ -89,22 +88,26 @@ static void real_main(void)
     shutdownHaskellAndExit(exit_status);
 }
 
-/* The rts entry point from a compiled program using a Haskell main function.
- * This gets called from a tiny main function which gets linked into each
- * compiled Haskell program that uses a Haskell main function.
+/* The rts entry point from a compiled program using a Haskell main
+ * function.  This gets called from a tiny main function generated by
+ * GHC and linked into each compiled Haskell program that uses a
+ * Haskell main function.
  *
  * We expect the caller to pass ZCMain_main_closure for
  * main_closure. The reason we cannot refer to this symbol directly
  * is because we're inside the rts and we do not know for sure that
  * we'll be using a Haskell main function.
  */
-int hs_main(int argc, char *argv[], StgClosure *main_closure)
+int hs_main (int argc, char *argv[],     // program args
+             StgClosure *main_closure,   // closure for Main.main
+             RtsConfig rts_config)    // RTS configuration
 {
     /* We do this dance with argc and argv as otherwise the SEH exception
        stuff (the BEGIN/END CATCH below) on Windows gets confused */
     progargc = argc;
     progargv = argv;
     progmain_closure = main_closure;
+    rtsconfig = rts_config;
 
 #if defined(mingw32_HOST_OS)
     BEGIN_CATCH