arm32 fails with glibc 2.31
gcc-6.5.0/gcc-6.5.0/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc:186:0:
gcc-6.5.0/gcc-6.5.0/libsanitizer/sanitizer_common/sanitizer_internal_defs.h:254:72: error: size of array 'assertion_failed__1139' is negative
     typedef char IMPL_PASTE(assertion_failed_##_, line)[2*(int)(pred)-1]


Glibc has recently introduced changed to the mode field in ipc_perm
in commit 2f959dfe849e0646e27403f2e4091536496ac0f0. For Arm this
means that the mode field no longer has the same size.

This causes an assert failure against libsanitizer's internal copy
of ipc_perm.  Since this change can't be easily detected I am adding
arm to the list of targets that are excluded from this check.  libsanitizer
doesn't use this field (and others, it in fact uses only 1 field) so this check
can be ignored.

Padding bits were used by glibc when the field was changed so sizeof and offsets
of the remaining fields should be the same.

This patch is backported from gcc 8.4.0 with the below reference
https://github.com/gcc-mirror/gcc/commit/761a3a95ee26d54fbb8351c15cf5773d58fc9f70
https://github.com/gcc-mirror/gcc/commit/dbdf86838aaaef76620c00c53096cfe157d5af6e

---
 .../sanitizer_common/sanitizer_platform_limits_posix.cc   |  5 +++--
 .../sanitizer_common/sanitizer_platform_limits_posix.h    | 15 +--------------
 2 files changed, 4 insertions(+), 16 deletions(-)

diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
index 8f96237..7eab667 100644
--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
+++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
@@ -1160,8 +1160,9 @@ CHECK_SIZE_AND_OFFSET(ipc_perm, uid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, gid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, cuid);
 CHECK_SIZE_AND_OFFSET(ipc_perm, cgid);
-#if !defined(__aarch64__) || !SANITIZER_LINUX || __GLIBC_PREREQ (2, 21)
-/* On aarch64 glibc 2.20 and earlier provided incorrect mode field.  */
+#if !SANITIZER_LINUX || __GLIBC_PREREQ (2, 31)
+/* glibc 2.30 and earlier provided 16-bit mode field instead of 32-bit
+   on many architectures.  */
 CHECK_SIZE_AND_OFFSET(ipc_perm, mode);
 #endif
 
diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
index 73af92a..6a673a7 100644
--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
+++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
@@ -211,26 +211,13 @@ namespace __sanitizer {
     u64 __unused1;
     u64 __unused2;
 #elif defined(__sparc__)
-#if defined(__arch64__)
     unsigned mode;
-    unsigned short __pad1;
-#else
-    unsigned short __pad1;
-    unsigned short mode;
     unsigned short __pad2;
-#endif
     unsigned short __seq;
     unsigned long long __unused1;
     unsigned long long __unused2;
-#elif defined(__mips__) || defined(__aarch64__) || defined(__s390x__)
-    unsigned int mode;
-    unsigned short __seq;
-    unsigned short __pad1;
-    unsigned long __unused1;
-    unsigned long __unused2;
 #else
-    unsigned short mode;
-    unsigned short __pad1;
+    unsigned int mode;
     unsigned short __seq;
     unsigned short __pad2;
 #if defined(__x86_64__) && !defined(_LP64)
-- 
2.7.4