This is a backport of this patch from 6.5 to 4.9:

  https://gcc.gnu.org/git/?p=gcc.git;a=patch;h=8937b94d1a643fd9760714642296d034a45254a8

diff --git a/libsanitizer/sanitizer_common/sanitizer_linux.cc b/libsanitizer/sanitizer_common/sanitizer_linux.cc
index 69c9c10..8e53673 100644
--- a/libsanitizer/sanitizer_common/sanitizer_linux.cc
+++ b/libsanitizer/sanitizer_common/sanitizer_linux.cc
@@ -599,8 +599,7 @@ uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5) {
   return internal_syscall(__NR_prctl, option, arg2, arg3, arg4, arg5);
 }
 
-uptr internal_sigaltstack(const struct sigaltstack *ss,
-                         struct sigaltstack *oss) {
+uptr internal_sigaltstack(const void *ss, void *oss) {
   return internal_syscall(__NR_sigaltstack, (uptr)ss, (uptr)oss);
 }
 
diff --git a/libsanitizer/sanitizer_common/sanitizer_linux.h b/libsanitizer/sanitizer_common/sanitizer_linux.h
index 6422df1..8a8e526 100644
--- a/libsanitizer/sanitizer_common/sanitizer_linux.h
+++ b/libsanitizer/sanitizer_common/sanitizer_linux.h
@@ -18,7 +18,6 @@
 #include "sanitizer_platform_limits_posix.h"
 
 struct link_map;  // Opaque type returned by dlopen().
-struct sigaltstack;
 
 namespace __sanitizer {
 // Dirent structure for getdents(). Note that this structure is different from
@@ -28,8 +27,7 @@ struct linux_dirent;
 // Syscall wrappers.
 uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count);
 uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5);
-uptr internal_sigaltstack(const struct sigaltstack* ss,
-                          struct sigaltstack* oss);
+uptr internal_sigaltstack(const void *ss, void *oss);
 uptr internal_sigaction(int signum, const __sanitizer_kernel_sigaction_t *act,
     __sanitizer_kernel_sigaction_t *oldact);
 uptr internal_sigprocmask(int how, __sanitizer_kernel_sigset_t *set,
diff --git a/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc b/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
index 6ee63ec..50c21a3 100644
--- a/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
+++ b/libsanitizer/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc
@@ -238,7 +238,7 @@ static int TracerThread(void* argument) {
 
   // Alternate stack for signal handling.
   InternalScopedBuffer<char> handler_stack_memory(kHandlerStackSize);
-  struct sigaltstack handler_stack;
+  stack_t handler_stack;
   internal_memset(&handler_stack, 0, sizeof(handler_stack));
   handler_stack.ss_sp = handler_stack_memory.data();
   handler_stack.ss_size = kHandlerStackSize;
diff --git a/libsanitizer/tsan/tsan_platform_linux.cc b/libsanitizer/tsan/tsan_platform_linux.cc
index fe69430..49f5270 100644
--- a/libsanitizer/tsan/tsan_platform_linux.cc
+++ b/libsanitizer/tsan/tsan_platform_linux.cc
@@ -351,7 +351,7 @@ bool IsGlobalVar(uptr addr) {
 // closes within glibc. The code is a pure hack.
 int ExtractResolvFDs(void *state, int *fds, int nfd) {
   int cnt = 0;
-  __res_state *statp = (__res_state*)state;
+  struct __res_state *statp = (struct __res_state*)state;
   for (int i = 0; i < MAXNS && cnt < nfd; i++) {
     if (statp->_u._ext.nsaddrs[i] && statp->_u._ext.nssocks[i] != -1)
       fds[cnt++] = statp->_u._ext.nssocks[i];
><td><a href='/guix/commit/gnu/packages/busybox.scm?id=ee0b4733e1a186048983ac6b6ba0bae23b3f567d'>gnu: toybox: Don't install files to usr.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2019-06-06 05:59:00 +0200'>2019-06-06</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=fcc7fa472b111e0916d96621bbf68f869358bdd9'>gnu: toybox: Update to 0.8.1.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-02-17 03:37:50 +0100'>2019-02-17</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=51e31aa865e5d1b272673ae94e13ffdc9f4db536'>gnu: toybox: Update to 0.8.0.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2018-12-12 09:27:17 +0200'>2018-12-12</span></td><td><a href='/guix/commit/gnu/packages/busybox.scm?id=42140fd434a333d0565617471b51323d6815ee13'>gnu: Add toybox.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>