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Enable Gnulib substitute on Android systems with defective strnlen

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* configure.ac (AC_FUNC_STRNLEN): Detect a bug where strnlen is
liable to integer overflows if addition of the search limit to
the string would also overflow.

* src/xdisp.c (store_mode_line_string): Remove stopgap measure.
This commit is contained in:
Po Lu 2024-07-05 12:09:52 +08:00
parent 507a13f5a1
commit 04d7318efa
2 changed files with 25 additions and 12 deletions
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24
configure.ac
View file

@ -1611,6 +1611,30 @@ AC_DEFUN([gl_TYPE_OFF64_T],
[HAVE_OFF64_T=1
AC_SUBST([HAVE_OFF64_T])])
# `strnlen' cannot accept nlen greater than the size of the object S
# on Android 2.2 and earlier.
m4_define([ORIGINAL_AC_FUNC_STRNLEN], m4_defn([AC_FUNC_STRNLEN]))
AC_DEFUN([AC_FUNC_STRNLEN], [
AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])dnl
AC_REQUIRE([AC_CANONICAL_HOST])dnl
AC_CACHE_CHECK([for strnlen capable of accepting large limits],
[emacs_cv_func_strnlen_working],
[AC_RUN_IFELSE([AC_LANG_PROGRAM([AC_INCLUDES_DEFAULT], [[
volatile size_t (*strnlen_pointer) (const char *s, size_t) = &strnlen;
if ((*strnlen_pointer) ("", -1) != 0)
return 1;
return 0;
]])],[emacs_cv_func_strnlen_working=yes],
[emacs_cv_func_strnlen_working=no],
[# Guess no on Android 21 and earlier, yes elsewhere.
AS_IF([test -n "$ANDROID_SDK" && test "$ANDROID_SDK" -lt 22],
[emacs_cv_func_strnlen_working=no],
[emacs_cv_func_strnlen_working='guessing yes'])])])
AS_IF([test "$emacs_cv_func_strnlen_working" != "no"],
[ORIGINAL_AC_FUNC_STRNLEN],
[ac_cv_func_strnlen_working=no
AC_LIBOBJ([strnlen])])])
# Initialize gnulib right after choosing the compiler.
dnl Amongst other things, this sets AR and ARFLAGS.
gl_EARLY

13
src/xdisp.c
View file

@ -28065,18 +28065,7 @@ store_mode_line_string (const char *string, Lisp_Object lisp_string,
if (string != NULL)
{
#if defined HAVE_ANDROID && !defined ANDROID_STUBIFY \
&& __ANDROID_API__ < 22
/* Circumvent a bug in memchr preventing strnlen from returning
valid values when a large limit is specified.
https://issuetracker.google.com/issues/37020957 */
if (precision <= 0 || ((uintptr_t) string
> (UINTPTR_MAX - precision)))
len = strlen (string);
else
#endif /* HAVE_ANDROID && !ANDROID_STUBIFY && __ANDROID_API__ < 22 */
len = strnlen (string, precision <= 0 ? SIZE_MAX : precision);
len = strnlen (string, precision <= 0 ? SIZE_MAX : precision);
lisp_string = make_string (string, len);
if (NILP (props))
props = mode_line_string_face_prop;