From 8e50a45f3e4de8086058be933e147e0509f40497 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby.or.jp>
Date: Fri, 14 Nov 2025 00:49:55 +0900
Subject: [PATCH] mrb_print_error: handle NULL gracefully to simplify error
 checking

made mrb_print_error() handle NULL by printing "Failed to allocate
mrb_state" when mrb is NULL. since mrb_close() already handles NULL,
this allows simplified error checking pattern:

  if (!MRB_OPEN_SUCCESS(mrb)) {
    mrb_print_error(mrb);  // handles NULL
    mrb_close(mrb);        // handles NULL
    return EXIT_FAILURE;
  }

updated all binary tools (mruby, mirb, mrdb, mrbtest) to use this
simplified pattern, removing nested if checks.

Co-authored-by: Claude <noreply@anthropic.com>
---
 mrbgems/mruby-bin-debugger/tools/mrdb/mrdb.c | 11 ++---------
 mrbgems/mruby-bin-mirb/tools/mirb/mirb.c     | 11 ++---------
 mrbgems/mruby-bin-mruby/tools/mruby/mruby.c  | 11 ++---------
 mrbgems/mruby-test/driver.c                  | 11 ++---------
 src/error.c                                  |  5 +++++
 5 files changed, 13 insertions(+), 36 deletions(-)

diff --git a/mrbgems/mruby-bin-debugger/tools/mrdb/mrdb.c b/mrbgems/mruby-bin-debugger/tools/mrdb/mrdb.c
index a135b0fa7..c2f736871 100644
--- a/mrbgems/mruby-bin-debugger/tools/mrdb/mrdb.c
+++ b/mrbgems/mruby-bin-debugger/tools/mrdb/mrdb.c
@@ -674,15 +674,8 @@ main(int argc, char **argv)
  l_restart:
 
   if (!MRB_OPEN_SUCCESS(mrb)) {
-    if (mrb) {
-      /* Initialization failed - print exception details */
-      mrb_print_error(mrb);
-      mrb_close(mrb);
-    }
-    else {
-      /* Allocation failed */
-      fputs("Failed to allocate mrb_state, exiting mrdb\n", stderr);
-    }
+    mrb_print_error(mrb);  /* handles NULL */
+    mrb_close(mrb);        /* handles NULL */
     return EXIT_FAILURE;
   }
 
diff --git a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
index 77ab8ce6b..c26dcfdd3 100644
--- a/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
+++ b/mrbgems/mruby-bin-mirb/tools/mirb/mirb.c
@@ -476,15 +476,8 @@ main(int argc, char **argv)
   /* new interpreter instance */
   mrb = mrb_open();
   if (!MRB_OPEN_SUCCESS(mrb)) {
-    if (mrb) {
-      /* Initialization failed - print exception details */
-      mrb_print_error(mrb);
-      mrb_close(mrb);
-    }
-    else {
-      /* Allocation failed */
-      fputs("Failed to allocate mrb_state, exiting mirb\n", stderr);
-    }
+    mrb_print_error(mrb);  /* handles NULL */
+    mrb_close(mrb);        /* handles NULL */
     return EXIT_FAILURE;
   }
 
diff --git a/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c b/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c
index 38274c399..fc56900c3 100644
--- a/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c
+++ b/mrbgems/mruby-bin-mruby/tools/mruby/mruby.c
@@ -283,15 +283,8 @@ main(int argc, char **argv)
   mrb_value v;
 
   if (!MRB_OPEN_SUCCESS(mrb)) {
-    if (mrb) {
-      /* Initialization failed - print exception details */
-      mrb_print_error(mrb);
-      mrb_close(mrb);
-    }
-    else {
-      /* Allocation failed */
-      fprintf(stderr, "%s: Failed to allocate mrb_state, exiting mruby\n", *argv);
-    }
+    mrb_print_error(mrb);  /* handles NULL */
+    mrb_close(mrb);        /* handles NULL */
     return EXIT_FAILURE;
   }
 
diff --git a/mrbgems/mruby-test/driver.c b/mrbgems/mruby-test/driver.c
index d1decad8b..7caecd54e 100644
--- a/mrbgems/mruby-test/driver.c
+++ b/mrbgems/mruby-test/driver.c
@@ -291,15 +291,8 @@ main(int argc, char **argv)
   /* new interpreter instance */
   mrb = mrb_open();
   if (!MRB_OPEN_SUCCESS(mrb)) {
-    if (mrb) {
-      /* Initialization failed - print exception details */
-      mrb_print_error(mrb);
-      mrb_close(mrb);
-    }
-    else {
-      /* Allocation failed */
-      fputs("Failed to allocate mrb_state, exiting test driver", stderr);
-    }
+    mrb_print_error(mrb);  /* handles NULL */
+    mrb_close(mrb);        /* handles NULL */
     return EXIT_FAILURE;
   }
 
diff --git a/src/error.c b/src/error.c
index ffb9e4792..487e1afc7 100644
--- a/src/error.c
+++ b/src/error.c
@@ -845,6 +845,11 @@ MRB_API void
 mrb_print_error(mrb_state *mrb)
 {
 #ifndef MRB_NO_STDIO
+  if (!mrb) {
+    /* mrb_open() returned NULL - allocation failed */
+    fputs("Failed to allocate mrb_state\n", stderr);
+    return;
+  }
   if (mrb->jmp == NULL) {
     struct mrb_jmpbuf c_jmp;
     MRB_TRY(&c_jmp) {