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];
610fa45dde7415ccbf07525d00e79'>gnu: serd: Update to 0.30.4.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-04-23 13:33:09 +0200'>2020-04-23</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=030f6f489fe9544f35ebaf95135acd1dd67ce63f'>Merge branch 'master' into core-updates</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-04-21 12:41:47 +0300'>2020-04-21</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=0e64f12db526dbb87ec0517b02ff2f997ab7ab63'>gnu: Add python-rdflib-jsonld.</a><span class='msg-avail'>...</span></td><td>Pjotr Prins</td></tr>
<tr><td><span title='2020-04-21 12:38:19 +0300'>2020-04-21</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=5d29808beaa0e68f33504c3a3bf6373b36dcabfa'>gnu: rdf.scm: Use license: prefix.</a><span class='msg-avail'>...</span></td><td>Efraim Flashner</td></tr>
<tr><td><span title='2020-03-27 00:12:15 +0100'>2020-03-27</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=18af6870370226b4d502d7372844e7f2aded5887'>Merge branch 'master' into core-updates</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-03-23 20:48:49 +0100'>2020-03-23</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=0a6f68982b950aed7444367cfe7f23123fa703e3'>gnu: sord: Add pcre to inputs.</a><span class='msg-avail'>...</span></td><td>Alexandros Theodotou</td></tr>
<tr><td><span title='2020-03-04 23:16:17 +0100'>2020-03-04</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=ebb7cf9e21060105d9950dd5142c0eb918083666'>Merge branch 'master' into core-updates</a></td><td>Marius Bakke</td></tr>
<tr><td><span title='2020-03-03 05:06:47 +0100'>2020-03-03</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=efebdf3a66490b59dbafe9904701eb9b27bdaac4'>gnu: serd: Update to 0.30.2.</a><span class='msg-avail'>...</span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2020-01-15 00:24:28 +0100'>2020-01-15</span></td><td><a href='/guix/commit/gnu/packages/rdf.scm?id=bb93042c8beb881ab907fa802eefb3c4091039a2'>gnu: util-linux: Move libraries to separate output.</a><span class='msg-avail'>...</span></td><td>Marius Bakke</td></tr>