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, 21 insertions, 0 deletions

diff --git a/includes/rts/Main.h b/includes/rts/Main.h
new file mode 100644
index 0000000000..1c332fc95c
--- /dev/null
+++ b/includes/rts/Main.h
@@ -0,0 +1,21 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 2009
+ *
+ * Entry point for standalone Haskell programs.
+ *
+ * ---------------------------------------------------------------------------*/
+
+#ifndef RTSMAIN_H
+#define RTSMAIN_H
+
+/* -----------------------------------------------------------------------------
+ * The entry point for Haskell programs that use a Haskell main function
+ * -------------------------------------------------------------------------- */
+
+int hs_main (int argc, char *argv[],     // program args
+             StgClosure *main_closure,   // closure for Main.main
+             RtsConfig rts_config)       // RTS configuration
+   GNUC3_ATTRIBUTE(__noreturn__);
+
+#endif /* RTSMAIN_H */