[PATCH 2/2] iconvdata: Test case for bug 34556

[Florian Weimer]

Assisted-by: LLM
---
 iconvdata/Makefile                      |   5 +-
 iconvdata/tst-shift-jisx0213-progress.c | 118 ++++++++++++++++++++++++
 2 files changed, 122 insertions(+), 1 deletion(-)
 create mode 100644 iconvdata/tst-shift-jisx0213-progress.c

diff --git a/iconvdata/Makefile b/iconvdata/Makefile
index fbb0067302..7343350a9a 100644
--- a/iconvdata/Makefile
+++ b/iconvdata/Makefile
@@ -76,7 +76,8 @@ tests = bug-iconv1 bug-iconv2 tst-loading tst-e2big tst-iconv4 bug-iconv4 \
 	tst-iconv6 bug-iconv5 bug-iconv6 tst-iconv7 bug-iconv8 bug-iconv9 \
 	bug-iconv10 bug-iconv11 bug-iconv12 tst-iconv-big5-hkscs-to-2ucs4 \
 	bug-iconv13 bug-iconv14 bug-iconv15 \
-	tst-iconv-iso-2022-cn-ext tst-bug33980
+	tst-iconv-iso-2022-cn-ext tst-bug33980 \
+	tst-shift-jisx0213-progress
 ifeq ($(have-thread-library),yes)
 tests += bug-iconv3
 endif
@@ -335,6 +336,8 @@ $(objpfx)tst-iconv-iso-2022-cn-ext.out: $(addprefix $(objpfx), $(gconv-modules))
 					$(addprefix $(objpfx),$(modules.so))
 $(objpfx)tst-bug33980.out: $(addprefix $(objpfx), $(gconv-modules)) \
 			   $(addprefix $(objpfx),$(modules.so))
+$(objpfx)tst-shift-jisx0213-progress.out: \
+  $(addprefix $(objpfx), $(gconv-modules)) $(addprefix $(objpfx),$(modules.so))
 
 $(objpfx)iconv-test.out: run-iconv-test.sh \
 			 $(addprefix $(objpfx), $(gconv-modules)) \
diff --git a/iconvdata/tst-shift-jisx0213-progress.c b/iconvdata/tst-shift-jisx0213-progress.c
new file mode 100644
index 0000000000..264b7141f5
--- /dev/null
+++ b/iconvdata/tst-shift-jisx0213-progress.c
@@ -0,0 +1,118 @@
+/* Test SHIFT_JISX0213 combining character conversion progress (bug 34556).
+   Copyright (C) 2026 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+/* SHIFT_JISX0213 bytes 0x82 0xF5 map to a combining sequence:
+   U+304B (HIRAGANA LETTER KA) + U+309A (COMBINING SEMI-VOICED SOUND
+   MARK).  When converting to UTF-32LE with a small output buffer, the
+   first code point is emitted and the second is queued in the
+   converter state.  This test verifies that the queued code point is
+   consumed exactly once on retry, so that the conversion makes
+   progress and terminates.  */
+
+#include <errno.h>
+#include <iconv.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <support/check.h>
+#include <support/support.h>
+
+static void
+test_one (size_t outbufsize)
+{
+  /* Combining sequence followed by a plain ASCII character.  */
+  char input[] = { '\x82', '\xf5', 'A' };
+
+  /* Expected UTF-32 output.  */
+  static const wchar_t expected[] = { 0x304b, 0x309a, 'A' };
+
+  iconv_t cd = iconv_open ("WCHAR_T", "SHIFT_JISX0213");
+  TEST_VERIFY_EXIT (cd != (iconv_t) -1);
+
+  char result[64];
+  size_t result_len = 0;
+
+  char *inptr = input;
+  size_t inleft = sizeof (input);
+
+  char outbuf[64];
+
+  int iterations = 0;
+  while (inleft > 0)
+    {
+      char *outptr = outbuf;
+      size_t outleft = outbufsize;
+      size_t inleft_before = inleft;
+
+      size_t ret = iconv (cd, &inptr, &inleft, &outptr, &outleft);
+      size_t produced = outptr - outbuf;
+
+      TEST_VERIFY_EXIT (result_len + produced <= sizeof (result));
+      memcpy (result + result_len, outbuf, produced);
+      result_len += produced;
+
+      if (ret == (size_t) -1 && errno == E2BIG)
+	{
+	  if (produced == 0 && inleft == inleft_before)
+	    {
+	      /* Output buffer too small for a single code point.  */
+	      TEST_VERIFY_EXIT (outbufsize < 4);
+	      break;
+	    }
+	  /* Bound iterations to detect non-progress bugs.  */
+	  TEST_VERIFY_EXIT (++iterations < 10);
+	  continue;
+	}
+      if (ret == (size_t) -1)
+	FAIL_EXIT1 ("outbufsize %zu: iconv: %m", outbufsize);
+      break;
+    }
+
+  /* Flush pending converter state.  */
+  {
+    char *outptr = outbuf;
+    size_t outleft = outbufsize;
+    size_t ret = iconv (cd, NULL, NULL, &outptr, &outleft);
+    TEST_VERIFY (ret == 0);
+    size_t produced = outptr - outbuf;
+    memcpy (result + result_len, outbuf, produced);
+    result_len += produced;
+  }
+
+  if (outbufsize >= 4)
+    {
+      TEST_COMPARE (inleft, 0);
+      TEST_COMPARE_BLOB (result, result_len,
+			 expected, sizeof (expected));
+    }
+
+  TEST_VERIFY_EXIT (iconv_close (cd) == 0);
+}
+
+static int
+do_test (void)
+{
+  for (size_t outbufsize = 1; outbufsize <= 16; outbufsize++)
+    {
+      printf ("info: testing output buffer size %zu\n", outbufsize);
+      test_one (outbufsize);
+    }
+  return 0;
+}
+
+#include <support/test-driver.c>
-- 
2.55.0