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Date:	Thu, 11 Aug 2022 21:18:06 +0900
From:	Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>
To:	cygwin AT cygwin DOT com
Subject:	Re: crash in newlocale()
Message-Id:	<20220811211806.bc7f5426ce52f57d1c1538c2@nifty.ne.jp>
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On Thu, 11 Aug 2022 11:29:28 +1000
Tony Cook wrote:
> Hello everyone,
> 
> While tracking down a crash in development versions of perl the boostrap
> miniperl executable was crashing early in the build process:
> 
> $ gdb --args ./miniperl -e0
> GNU gdb (GDB) (Cygwin 11.2-1) 11.2
> Copyright (C) 2022 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> Type "show copying" and "show warranty" for details.
> This GDB was configured as "x86_64-pc-cygwin".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <https://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
>     <http://www.gnu.org/software/gdb/documentation/>.
> 
> For help, type "help".
> Type "apropos word" to search for commands related to "word"...
> Reading symbols from ./miniperl...
> (gdb) b locale.c:1154
> Breakpoint 1 at 0x10077db13: file locale.c, line 1154.
> (gdb) r
> Starting program: /home/tony/dev/perl/git/perl/miniperl -e0
> [New Thread 13624.0x1c7c]
> [New Thread 13624.0x1978]
> [New Thread 13624.0x2958]
> [New Thread 13624.0x3374]
> 
> Thread 1 "miniperl" hit Breakpoint 1, S_emulate_setlocale_i (my_perl=0x800049910, index=0, new_locale=0x800066628 "en_US.UTF-8", recalc_LC_ALL=-1, line=4026) at locale.c:1154
> 1154            new_obj = newlocale(mask, new_locale, basis_obj);
> (gdb) bt
> #0  S_emulate_setlocale_i (my_perl=0x800049910, index=0,
>     new_locale=0x800066628 "en_US.UTF-8", recalc_LC_ALL=-1, line=4026)
>     at locale.c:1154
> #1  0x0000000100783849 in Perl_init_i18nl10n (my_perl=0x800049910, printwarn=1)
>     at locale.c:4026
> #2  0x0000000100443c80 in perl_construct (my_perl=0x800049910)
>     at /home/tony/dev/perl/git/perl/perl.c:447
> #3  0x00000001007b7483 in main (argc=2, argv=0xffffcc30, env=0x8000281a0)
>     at miniperlmain.c:108
> (gdb) p mask
> $1 = 4
> (gdb) p new_locale
> $2 = 0x800066628 "en_US.UTF-8"
> (gdb) p basis_obj
> $3 = (locale_t) 0x1802b3060 <__C_locale>
> (gdb) n
> 
> Thread 1 "miniperl" received signal SIGSEGV, Segmentation fault.
> 0x000000080004a310 in ?? ()
> (gdb) bt
> #0  0x000000080004a310 in ?? ()
> Backtrace stopped: previous frame identical to this frame (corrupt stack?)
> (gdb)
> 
> While I get a SEGV from miniperl, a simple reproducer returns a
> SIGTRAP:
> 
> tony AT enceladus ~/dev/perl/git
> $ cat newlocale-test.c
> #include <locale.h>
> #include <stdio.h>
> 
> int main() {
>   locale_t st = newlocale(LC_ALL_MASK, "C", (locale_t)0);
> 
>   locale_t st2 = newlocale(LC_CTYPE_MASK, "en_US.UTF-8", st);
>   printf("Done\n");
>   return 0;
> }
> tony AT enceladus ~/dev/perl/git
> $ gcc -onewlocale-test -g newlocale-test.c
> 
> tony AT enceladus ~/dev/perl/git
> $ gdb ./newlocale-test.exe
> GNU gdb (GDB) (Cygwin 11.2-1) 11.2
> Copyright (C) 2022 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> Type "show copying" and "show warranty" for details.
> This GDB was configured as "x86_64-pc-cygwin".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <https://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
>     <http://www.gnu.org/software/gdb/documentation/>.
> 
> For help, type "help".
> Type "apropos word" to search for commands related to "word"...
> Reading symbols from ./newlocale-test.exe...
> (gdb) r
> Starting program: /home/tony/dev/perl/git/newlocale-test.exe
> [New Thread 9176.0x3a8c]
> [New Thread 9176.0x2014]
> [New Thread 9176.0x2bc4]
> [Thread 9176.0x2014 exited with code 3221225477]
> [Thread 9176.0x3a8c exited with code 3221225477]
> [Thread 9176.0x2bc4 exited with code 3221225477]
> 
> Program terminated with signal SIGTRAP, Trace/breakpoint trap.
> The program no longer exists.
> (gdb) b main
> Breakpoint 1 at 0x10040108d: file newlocale-test.c, line 5.
> (gdb) r
> Starting program: /home/tony/dev/perl/git/newlocale-test.exe
> [New Thread 13668.0x2a7c]
> [New Thread 13668.0x15a0]
> [New Thread 13668.0x2158]
> 
> Thread 1 "newlocale-test" hit Breakpoint 1, main () at newlocale-test.c:5
> 5         locale_t st = newlocale(LC_ALL_MASK, "C", (locale_t)0);
> (gdb) n
> 7         locale_t st2 = newlocale(LC_CTYPE_MASK, "en_US.UTF-8", st);
> (gdb)
> [Thread 13668.0x2158 exited with code 3221225477]
> [Thread 13668.0x35d0 exited with code 3221225477]
> [Thread 13668.0x2a7c exited with code 3221225477]
> 
> Program terminated with signal SIGTRAP, Trace/breakpoint trap.
> The program no longer exists.
> (gdb)

I looked into this problem and found the access violation
occurs at:
newlib/libc/locale/newlocale.c
@@ 188,7 @@ _newlocale_r (struct _reent *p, int category_mask, const char *locale,
	if (tmp_locale.lc_cat[i].buf == (const void *) -1)
	  {
	    tmp_locale.lc_cat[i].buf = base->lc_cat[i].buf;
	    base->lc_cat[i].ptr = base->lc_cat[i].buf = NULL; <-- Here!!!
	  }
#endif /* __HAVE_LOCALE_INFO__ */
      _freelocale_r (p, base);

This is because
locale_t st = newlocale(LC_ALL_MASK, "C", (locale_t)0);
returns
  extern const struct __locale_t __C_locale;
  return (struct __locale_t *) &__C_locale;
, which is in the const area that cannot be modified.

This seems to be a newlib bug.

I also found following patch solves the issue.

diff --git a/newlib/libc/locale/newlocale.c b/newlib/libc/locale/newlocale.c
index 0789d5fd9..1974665ec 100644
--- a/newlib/libc/locale/newlocale.c
+++ b/newlib/libc/locale/newlocale.c
@@ -108,10 +108,12 @@ _newlocale_r (struct _reent *p, int category_mask, const char *locale,
     }
   /* If the new locale is supposed to be all default locale, just return
      a pointer to the default locale. */
+#if 0
   if ((!base && category_mask == 0)
       || (category_mask == LC_VALID_MASK
 	  && (!strcmp (locale, "C") || !strcmp (locale, "POSIX"))))
     return __get_C_locale ();
+#endif
   /* Start with setting all values to the default locale values. */
   tmp_locale = *__get_C_locale ();
   /* Fill out new category strings. */

-- 
Takashi Yano <takashi DOT yano AT nifty DOT ne DOT jp>

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