Revert "Load external GC using command line argument"

This reverts commit 8ddb1110c283c5cb59b6582383f36fdbcc43ab19.

gc.c

@@ -748,26 +748,19 @@ typedef struct gc_function_map {
 
 static rb_gc_function_map_t rb_gc_functions;
 
-# define RUBY_GC_LIBRARY_ARG "--gc-library="
+# define RUBY_GC_LIBRARY_PATH "RUBY_GC_LIBRARY_PATH"
 
-void
-ruby_load_external_gc_from_argv(int argc, char **argv)
+static void
+ruby_external_gc_init(void)
 {
-    char *gc_so_path = NULL;
-
-    for (int i = 0; i < argc; i++) {
-        if (strncmp(argv[i], RUBY_GC_LIBRARY_ARG, sizeof(RUBY_GC_LIBRARY_ARG) - 1) == 0) {
-            gc_so_path = argv[i] + sizeof(RUBY_GC_LIBRARY_ARG) - 1;
-        }
-    }
-
+    char *gc_so_path = getenv(RUBY_GC_LIBRARY_PATH);
     void *handle = NULL;
     if (gc_so_path && dln_supported_p()) {
         char error[1024];
         handle = dln_open(gc_so_path, error, sizeof(error));
         if (!handle) {
             fprintf(stderr, "%s", error);
-            rb_bug("ruby_load_external_gc_from_argv: Shared library %s cannot be opened", gc_so_path);
+            rb_bug("ruby_external_gc_init: Shared library %s cannot be opened", gc_so_path);
         }
     }
 
@@ -775,7 +768,7 @@ ruby_load_external_gc_from_argv(int argc, char **argv)
     if (handle) { \
         rb_gc_functions.name = dln_symbol(handle, "rb_gc_impl_" #name); \
         if (!rb_gc_functions.name) { \
-            rb_bug("ruby_load_external_gc_from_argv: " #name " func not exported by library %s", gc_so_path); \
+            rb_bug("ruby_external_gc_init: " #name " func not exported by library %s", gc_so_path); \
         } \
     } \
     else { \
@@ -938,6 +931,10 @@ ruby_load_external_gc_from_argv(int argc, char **argv)
 void *
 rb_objspace_alloc(void)
 {
+#if USE_SHARED_GC
+    ruby_external_gc_init();
+#endif
+
     void *objspace = rb_gc_impl_objspace_alloc();
     ruby_current_vm_ptr->objspace = objspace;
 
@@ -4627,6 +4624,12 @@ rb_obj_info_dump_loc(VALUE obj, const char *file, int line, const char *func)
 void
 Init_GC(void)
 {
+#if USE_SHARED_GC
+    if (getenv(RUBY_GC_LIBRARY_PATH) != NULL && !dln_supported_p()) {
+        rb_warn(RUBY_GC_LIBRARY_PATH " is ignored because this executable file can't load extension libraries");
+    }
+#endif
+
 #undef rb_intern
     malloc_offset = gc_compute_malloc_offset();
 

main.c

@@ -39,9 +39,6 @@ static int
 rb_main(int argc, char **argv)
 {
     RUBY_INIT_STACK;
-#if USE_SHARED_GC
-    ruby_load_external_gc_from_argv(argc, argv);
-#endif
     ruby_init();
     return ruby_run_node(ruby_options(argc, argv));
 }

ruby.c

@@ -1441,16 +1441,6 @@ proc_long_options(ruby_cmdline_options_t *opt, const char *s, long argc, char **
     else if (is_option_with_arg("source-encoding", Qfalse, Qtrue)) {
         set_source_encoding_once(opt, s, 0);
     }
-#endif
-#if defined(USE_SHARED_GC) && USE_SHARED_GC
-    else if (is_option_with_arg("gc-library", Qfalse, Qfalse)) {
-        // no-op
-        // Handled by ruby_load_external_gc_from_argv
-
-        if (!dln_supported_p()) {
-            rb_warn("--gc-library is ignored because this executable file can't load extension libraries");
-        }
-    }
 #endif
     else if (strcmp("version", s) == 0) {
         if (envopt) goto noenvopt_long;