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, 13 insertions, 1 deletions

diff --git a/rts/RtsStartup.c b/rts/RtsStartup.c
index de8bf792c4..e8ed86c994 100755
--- a/rts/RtsStartup.c
+++ b/rts/RtsStartup.c
@@ -71,6 +71,11 @@ static int hs_init_count = 0;
 
 static void flushStdHandles(void);
 
+const RtsConfig defaultRtsConfig  = {
+    .rts_opts_enabled = RtsOptsSafeOnly,
+    .rts_opts = NULL
+};
+
 /* -----------------------------------------------------------------------------
    Initialise floating point unit on x86 (currently disabled; See Note
    [x86 Floating point precision] in compiler/nativeGen/X86/Instr.hs)
@@ -106,6 +111,12 @@ x86_init_fpu ( void )
 void
 hs_init(int *argc, char **argv[])
 {
+    hs_init_ghc(argc, argv, defaultRtsConfig);
+}
+
+void
+hs_init_ghc(int *argc, char **argv[], RtsConfig rts_config)
+{
     hs_init_count++;
     if (hs_init_count > 1) {
 	// second and subsequent inits are ignored
@@ -132,7 +143,8 @@ hs_init(int *argc, char **argv[])
     /* Parse the flags, separating the RTS flags from the programs args */
     if (argc != NULL && argv != NULL) {
 	setFullProgArgv(*argc,*argv);
-        setupRtsFlags(argc, *argv);
+        setupRtsFlags(argc, *argv,
+                      rts_config.rts_opts_enabled, rts_config.rts_opts);
     }
 
     /* Initialise the stats department, phase 1 */