add UNREACHABLE_RETURN

Not every compilers understand that rb_raise does not return.  When a
function does not end with a return statement, such compilers can issue
warnings.  We would better tell them about reachabilities.

error.c

@@ -930,6 +930,7 @@ rb_check_typeddata(VALUE obj, const rb_data_type_t *data_type)
     const char *expected = data_type->wrap_struct_name;
     rb_raise(rb_eTypeError, "wrong argument type %"PRIsVALUE" (expected %s)",
              actual, expected);
+    UNREACHABLE_RETURN(NULL);
 }
 
 /* exception classes */

file.c

@@ -5433,6 +5433,7 @@ rb_f_test(int argc, VALUE *argv, VALUE _)
     else {
         rb_raise(rb_eArgError, "unknown command \"\\x%02X\"", cmd);
     }
+    UNREACHABLE_RETURN(Qundef);
 }
 
 

io.c

@@ -4199,6 +4199,7 @@ rb_io_each_codepoint(VALUE io)
 
   invalid:
     rb_raise(rb_eArgError, "invalid byte sequence in %s", rb_enc_name(enc));
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*
@@ -5578,6 +5579,7 @@ rb_io_modestr_fmode(const char *modestr)
 
   error:
     rb_raise(rb_eArgError, "invalid access mode %s", modestr);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 int

numeric.c

@@ -4013,6 +4013,7 @@ fix_pow_inverted(VALUE x, VALUE minusb)
 {
     if (x == INT2FIX(0)) {
         rb_num_zerodiv();
+        UNREACHABLE_RETURN(Qundef);
     }
     else {
         VALUE y = rb_int_pow(x, minusb);

object.c

@@ -2574,6 +2574,7 @@ rb_mod_const_get(int argc, VALUE *argv, VALUE mod)
 
   wrong_name:
     rb_name_err_raise(wrong_constant_name, mod, name);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*
@@ -2752,6 +2753,7 @@ rb_mod_const_defined(int argc, VALUE *argv, VALUE mod)
 
   wrong_name:
     rb_name_err_raise(wrong_constant_name, mod, name);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*
@@ -2904,6 +2906,7 @@ rb_mod_const_source_location(int argc, VALUE *argv, VALUE mod)
 
   wrong_name:
     rb_name_err_raise(wrong_constant_name, mod, name);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*
@@ -3607,8 +3610,10 @@ rb_cstr_to_dbl_raise(const char *p, int badcheck, int raise, int *error)
     return d;
 
   bad:
-    if (raise)
+    if (raise) {
         rb_invalid_str(q, "Float()");
+        UNREACHABLE_RETURN(nan(""));
+    }
     else {
         if (error) *error = 1;
         return 0.0;

proc.c

@@ -549,6 +549,7 @@ bind_local_variable_get(VALUE bindval, VALUE sym)
   undefined:
     rb_name_err_raise("local variable `%1$s' is not defined for %2$s",
                       bindval, sym);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*
@@ -2021,6 +2022,7 @@ rb_obj_singleton_method(VALUE obj, VALUE vid)
   /* undef: */
     rb_name_err_raise("undefined singleton method `%1$s' for `%2$s'",
                       obj, vid);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*

process.c

@@ -1900,6 +1900,7 @@ check_exec_redirect_fd(VALUE v, int iskey)
 
   wrong:
     rb_raise(rb_eArgError, "wrong exec redirect");
+    UNREACHABLE_RETURN(Qundef);
 }
 
 static VALUE

range.c

@@ -836,6 +836,7 @@ range_each_bignum_endless(VALUE beg)
     for (;; beg = rb_big_plus(beg, INT2FIX(1))) {
         rb_yield(beg);
     }
+    UNREACHABLE;
 }
 
 RBIMPL_ATTR_NORETURN()
@@ -847,6 +848,7 @@ range_each_fixnum_endless(VALUE beg)
     }
 
     range_each_bignum_endless(LONG2NUM(RUBY_FIXNUM_MAX + 1));
+    UNREACHABLE;
 }
 
 static VALUE

signal.c

@@ -274,6 +274,7 @@ signm2signo(VALUE *sig_ptr, int negative, int exit, int *prefix_ptr)
     }
     rb_raise(rb_eArgError, "unsupported signal `%.*s%"PRIsVALUE"'",
              prefix, signame_prefix, vsig);
+    UNREACHABLE_RETURN(0);
 }
 
 static const char*

string.c

@@ -3015,6 +3015,7 @@ rb_enc_cr_str_buf_cat(VALUE str, const char *ptr, long len,
   incompatible:
     rb_raise(rb_eEncCompatError, "incompatible character encodings: %s and %s",
              rb_enc_name(str_enc), rb_enc_name(ptr_enc));
+    UNREACHABLE_RETURN(Qundef);
 }
 
 VALUE
@@ -9679,6 +9680,7 @@ rb_str_crypt(VALUE str, VALUE salt)
 
   short_salt:
     rb_raise(rb_eArgError, "salt too short (need >=2 bytes)");
+    UNREACHABLE_RETURN(Qundef);
 }
 
 

thread.c

@@ -5175,6 +5175,7 @@ exec_recursive(VALUE (*func) (VALUE, VALUE, int), VALUE obj, VALUE pairid, VALUE
     rb_raise(rb_eTypeError, "invalid inspect_tbl pair_list "
              "for %+"PRIsVALUE" in %+"PRIsVALUE,
              sym, rb_thread_current());
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /*

time.c

@@ -5434,6 +5434,7 @@ end_submicro: ;
 
   invalid_format:
     rb_raise(rb_eTypeError, "marshaled time format differ");
+    UNREACHABLE_RETURN(Qundef);
 }
 
 /* :nodoc: */

variable.c

@@ -277,6 +277,7 @@ rb_path_to_class(VALUE pathname)
   undefined_class:
     rb_raise(rb_eArgError, "undefined class/module % "PRIsVALUE,
              rb_str_subseq(pathname, 0, p-path));
+    UNREACHABLE_RETURN(Qundef);
 }
 
 VALUE
@@ -3347,6 +3348,7 @@ rb_mod_remove_cvar(VALUE mod, VALUE name)
   not_defined:
     rb_name_err_raise("class variable %1$s not defined for %2$s",
                       mod, name);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 VALUE

vm_eval.c

@@ -846,6 +846,7 @@ method_missing(VALUE obj, ID id, int argc, const VALUE *argv, enum method_missin
     return result;
   missing:
     raise_method_missing(ec, argc, argv, obj, call_status | MISSING_MISSING);
+    UNREACHABLE_RETURN(Qundef);
 }
 
 #ifndef MJIT_HEADER