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, 0 insertions, 14 deletions

diff --git a/rts/hooks/RtsOpts.c b/rts/hooks/RtsOpts.c
deleted file mode 100644
index 2aae37246e..0000000000
--- a/rts/hooks/RtsOpts.c
+++ /dev/null
@@ -1,14 +0,0 @@
-/* -----------------------------------------------------------------------------
- *
- * Default RTS options.
- *
- * ---------------------------------------------------------------------------*/
-
-#include "PosixSource.h"
-#include "Rts.h"
-
-#include <stdlib.h>
-
-// Default RTS options can be given by providing an alternate
-// definition for this variable, pointing to a string of RTS options.
-char *ghc_rts_opts = NULL;