Fix range of `--backtrace-limit`

Also an option command line should have precedence over `RUBYOPT`.

internal/cmdlineopt.h

@@ -23,7 +23,7 @@ typedef struct ruby_cmdline_options {
     ruby_features_t features;
     ruby_features_t warn;
     unsigned int dump;
-    int backtrace_length_limit;
+    long backtrace_length_limit;
 #if USE_RJIT
     struct rb_rjit_options rjit;
 #endif

ruby.c

@@ -203,6 +203,10 @@ enum {
         )
 };
 
+#define BACKTRACE_LENGTH_LIMIT_VALID_P(n) ((n) >= -1)
+#define OPT_BACKTRACE_LENGTH_LIMIT_VALID_P(opt) \
+    BACKTRACE_LENGTH_LIMIT_VALID_P((opt)->backtrace_length_limit)
+
 static ruby_cmdline_options_t *
 cmdline_options_init(ruby_cmdline_options_t *opt)
 {
@@ -217,7 +221,7 @@ cmdline_options_init(ruby_cmdline_options_t *opt)
 #elif defined(YJIT_FORCE_ENABLE)
     opt->features.set |= FEATURE_BIT(yjit);
 #endif
-    opt->backtrace_length_limit = -1;
+    opt->backtrace_length_limit = LONG_MIN;
 
     return opt;
 }
@@ -893,7 +897,6 @@ moreswitches(const char *s, ruby_cmdline_options_t *opt, int envopt)
     VALUE int_enc_name = opt->intern.enc.name;
     ruby_features_t feat = opt->features;
     ruby_features_t warn = opt->warn;
-    int backtrace_length_limit = opt->backtrace_length_limit;
 
     while (ISSPACE(*s)) s++;
     if (!*s) return;
@@ -944,9 +947,6 @@ moreswitches(const char *s, ruby_cmdline_options_t *opt, int envopt)
     }
     FEATURE_SET_RESTORE(opt->features, feat);
     FEATURE_SET_RESTORE(opt->warn, warn);
-    if (backtrace_length_limit >= 0) {
-        opt->backtrace_length_limit = backtrace_length_limit;
-    }
 
     ruby_xfree(ptr);
     /* get rid of GC */
@@ -1450,8 +1450,12 @@ proc_long_options(ruby_cmdline_options_t *opt, const char *s, long argc, char **
     else if (is_option_with_arg("backtrace-limit", Qfalse, Qtrue)) {
         char *e;
         long n = strtol(s, &e, 10);
-        if (errno == ERANGE || n < -1 || *e) rb_raise(rb_eRuntimeError, "wrong limit for backtrace length");
-        opt->backtrace_length_limit = (int)n;
+        if (errno == ERANGE || !BACKTRACE_LENGTH_LIMIT_VALID_P(n) || *e) {
+            rb_raise(rb_eRuntimeError, "wrong limit for backtrace length");
+        }
+        else if (!OPT_BACKTRACE_LENGTH_LIMIT_VALID_P(opt)) {
+            opt->backtrace_length_limit = n;
+        }
     }
     else {
         rb_raise(rb_eRuntimeError,
@@ -2335,7 +2339,7 @@ process_options(int argc, char **argv, ruby_cmdline_options_t *opt)
     }
     if (opt->dump & dump_exit_bits) return Qtrue;
 
-    if (opt->backtrace_length_limit >= 0) {
+    if (OPT_BACKTRACE_LENGTH_LIMIT_VALID_P(opt)) {
         rb_backtrace_length_limit = opt->backtrace_length_limit;
     }
 

test/ruby/test_rubyoptions.rb

@@ -84,9 +84,14 @@ class TestRubyOptions < Test::Unit::TestCase
                        /^\t \.{3} \d+ levels\.{3}\n/])
     assert_kind_of(Integer, Thread::Backtrace.limit)
     assert_in_out_err(%w(--backtrace-limit=1), "p Thread::Backtrace.limit", ['1'], [])
+    assert_in_out_err(%w(--backtrace-limit 1), "p Thread::Backtrace.limit", ['1'], [])
     env = {"RUBYOPT" => "--backtrace-limit=5"}
     assert_in_out_err([env], "p Thread::Backtrace.limit", ['5'], [])
     assert_in_out_err([env, "--backtrace-limit=1"], "p Thread::Backtrace.limit", ['1'], [])
+    assert_in_out_err([env, "--backtrace-limit=-1"], "p Thread::Backtrace.limit", ['-1'], [])
+    long_max = RbConfig::LIMITS["LONG_MAX"]
+    assert_in_out_err(%W(--backtrace-limit=#{long_max}), "p Thread::Backtrace.limit",
+                      ["#{long_max}"], [])
   end
 
   def test_warning