Fix sanitizer build against latest glibc

[jakubjelinek]

Summary

libsanitizer doesn't build against latest glibc anymore, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81066 for details.
One of the changes is that stack_t changed from typedef struct sigaltstack { ... } stack_t; to typedef struct { ... } stack_t; for conformance reasons.
And the other change is that the glibc internal __need_res_state macro is now ignored, so when doing

#define __need_res_state
#include <resolv.h>

the effect is now the same as just

#include <resolv.h>

and thus one doesn't get just the

struct __res_state { ... };

definition, but newly also the

extern struct __res_state *__res_state(void) __attribute__ ((__const__));

prototype. So __res_state is no longer a type, but a function.

[jakubjelinek]

Using stack_t in the internal_sigaltstack prototype is problematic, because stack_t is only defined in the *.cc file which includes signal.h through sys/wait.h. But describing what it points to isn't really necessary, the function could be also declared with uptr arguments, or sanitizer_stack_t if we define it independently, etc.
Alternative to using struct res_state * is using res_state, i.e.

res_state statp = (res_state)state;

[kcc]

LGTM (assuming it will keep working with older glibc)
Thanks!

[jakubjelinek]

Could somebody please commit it? Thanks.

In D35246#805654, @kcc wrote:

LGTM (assuming it will keep working with older glibc)

Yes, both struct __res_state and stack_t should work even with very old glibc, looked at glibc 2.5.

[kcc]

In D35246#808324, @jakubjelinek wrote:

Could somebody please commit it? Thanks.

Will do later today.
Meanwhile, I'm pretty sure you'll get commit access if you request it.
http://llvm.org/docs/DeveloperPolicy.html#obtaining-commit-access

In D35246#805654, @kcc wrote:

LGTM (assuming it will keep working with older glibc)

Yes, both struct __res_state and stack_t should work even with very old glibc, looked at glibc 2.5.

[octoploid]

It isn't enough:

/home/markus/llvm/compiler-rt/lib/esan/esan_sideline_linux.cpp: In static member function ‘static int __esan::SidelineThread::runSideline(void*)’:                                 
/home/markus/llvm/compiler-rt/lib/esan/esan_sideline_linux.cpp:73:22: error: aggregate ‘__esan::SidelineThread::runSideline(void*)::sigaltstack SigAltStack’ has incomplete type and cannot be defined
   struct sigaltstack SigAltStack;          
                      ^~~~~~~~~~~

diff --git a/compiler-rt/lib/esan/esan_sideline_linux.cpp b/compiler-rt/lib/esan/esan_sideline_linux.cpp                                                                           
index d04f5909d6a2..bc272dfe49f8 100644     
--- a/compiler-rt/lib/esan/esan_sideline_linux.cpp                                       
+++ b/compiler-rt/lib/esan/esan_sideline_linux.cpp                                       
@@ -70,7 +70,7 @@ int SidelineThread::runSideline(void *Arg) {                           
                                            
   // Set up a signal handler on an alternate stack for safety.                          
   InternalScopedBuffer<char> StackMap(SigAltStackSize);                                 
-  struct sigaltstack SigAltStack;          
+  stack_t SigAltStack;                     
   SigAltStack.ss_sp = StackMap.data();     
   SigAltStack.ss_size = SigAltStackSize;   
   SigAltStack.ss_flags = 0;

lib/sanitizer_common/sanitizer_linux.h

 #include "sanitizer_platform.h"
 #if SANITIZER_FREEBSD || SANITIZER_LINUX
 #include "sanitizer_common.h"
 #include "sanitizer_internal_defs.h"
 #include "sanitizer_posix.h"
 #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
 // the one in <dirent.h>, which is used by readdir().
 struct linux_dirent;
 
 // Syscall wrappers.
 uptr internal_getdents(fd_t fd, struct linux_dirent *dirp, unsigned int count);
-uptr internal_sigaltstack(const struct sigaltstack* ss,
-                          struct sigaltstack* oss);
+uptr internal_sigaltstack(const void* ss, void* oss);
 uptr internal_sigprocmask(int how, __sanitizer_sigset_t *set,
     __sanitizer_sigset_t *oldset);
 
 // Linux-only syscalls.
 #if SANITIZER_LINUX
 uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5);
 // Used only by sanitizer_stoptheworld. Signal handlers that are actually used
 // (like the process-wide error reporting SEGV handler) must use

lib/sanitizer_common/sanitizer_linux.cc

 }
 
 #if SANITIZER_LINUX
 uptr internal_prctl(int option, uptr arg2, uptr arg3, uptr arg4, uptr arg5) {
   return internal_syscall(SYSCALL(prctl), option, arg2, arg3, arg4, arg5);
 }
 #endif
 
-uptr internal_sigaltstack(const struct sigaltstack *ss,
-                         struct sigaltstack *oss) {
+uptr internal_sigaltstack(const void *ss, void *oss) {
   return internal_syscall(SYSCALL(sigaltstack), (uptr)ss, (uptr)oss);
 }
 
 int internal_fork() {
 #if SANITIZER_USES_CANONICAL_LINUX_SYSCALLS
   return internal_syscall(SYSCALL(clone), SIGCHLD, 0);
 #else
   return internal_syscall(SYSCALL(fork));

lib/sanitizer_common/sanitizer_stoptheworld_linux_libcdep.cc

static int TracerThread(void* argument) {
   RAW_CHECK(AddDieCallback(TracerThreadDieCallback));
 
   ThreadSuspender thread_suspender(internal_getppid(), tracer_thread_argument);
   // Global pointer for the signal handler.
   thread_suspender_instance = &thread_suspender;
 
   // 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;
   internal_sigaltstack(&handler_stack, nullptr);
 
   // Install our handler for synchronous signals. Other signals should be
   // blocked by the mask we inherited from the parent thread.
   for (uptr i = 0; i < ARRAY_SIZE(kSyncSignals); i++) {

lib/tsan/rtl/tsan_platform_linux.cc

 
 #if !SANITIZER_GO
 // Extract file descriptors passed to glibc internal __res_iclose function.
 // This is required to properly "close" the fds, because we do not see internal
 // closes within glibc. The code is a pure hack.
 int ExtractResolvFDs(void *state, int *fds, int nfd) {
 #if SANITIZER_LINUX && !SANITIZER_ANDROID
   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];
   }
   return cnt;
 #else
   return 0;
 #endif