Fix undefined behavior in AC_SYS_LARGEFILE

* lib/autoconf/specific.m4 (_AC_SYS_LARGEFILE_TEST_INCLUDES):
Avoid undefined behavior on platforms where off_t is 32 bits.  See:
https://bugs.debian.org/742780

diff --git a/lib/autoconf/specific.m4 b/lib/autoconf/specific.m4
index 2809c00971b4040a53688e5b84b7bde6ec709880..f750722ac6d8a912071436080f88cec4fdfe580c 100644 (file)
--- a/lib/autoconf/specific.m4
+++ b/lib/autoconf/specific.m4
@@ -93,7 +93,7 @@ m4_define([_AC_SYS_LARGEFILE_TEST_INCLUDES],
     We can't simply define LARGE_OFF_T to be 9223372036854775807,
     since some C++ compilers masquerading as C compilers
     incorrectly reject 9223372036854775807.  */
-@%:@define LARGE_OFF_T (((off_t) 1 << 62) - 1 + ((off_t) 1 << 62))
+@%:@define LARGE_OFF_T (((off_t) 1 << 31 << 31) - 1 + ((off_t) 1 << 31 << 31))
   int off_t_is_large[[(LARGE_OFF_T % 2147483629 == 721
                       && LARGE_OFF_T % 2147483647 == 1)
                      ? 1 : -1]];[]dnl