[sanitizer] Move the errno/ENOMEM allocator checks logic to separate .cc

[cryptoad]

Summary

The fact that sanitizer_allocator_checks.h is including sanitizer_errno.h
creates complications for future changes, where it would conflict with errno.h
definitions on Android and Fuchsia (macro redefinition).

By moving the portion that sets errno in the checks to a separate compilation
unit, we avoid the inclusion of the header there, which solves the issue.

Not that it is not vital to have that function in a header as it is called as a
result of an unlikely event, and doesn't need to be inlined.

[alekseyshl]

lib/sanitizer_common/sanitizer_allocator_checks.cc

10

Fix this comment (I guess, copying your comment from the header file is enough).

[cryptoad]

Updating .cc file comment.

lib/sanitizer_common/CMakeLists.txt

 # Build system for the common Sanitizer runtime support library components.
 # These components are shared between AddressSanitizer and ThreadSanitizer.
 
 set(SANITIZER_SOURCES_NOTERMINATION
   sanitizer_allocator.cc
+  sanitizer_allocator_checks.cc
   sanitizer_common.cc
   sanitizer_deadlock_detector1.cc
   sanitizer_deadlock_detector2.cc
   sanitizer_errno.cc
   sanitizer_file.cc
   sanitizer_flags.cc
   sanitizer_flag_parser.cc
   sanitizer_fuchsia.cc

lib/sanitizer_common/sanitizer_allocator_checks.h

 // Various checks shared between ThreadSanitizer, MemorySanitizer, etc. memory
 // allocators.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef SANITIZER_ALLOCATOR_CHECKS_H
 #define SANITIZER_ALLOCATOR_CHECKS_H
 
-#include "sanitizer_errno.h"
 #include "sanitizer_internal_defs.h"
 #include "sanitizer_common.h"
 #include "sanitizer_platform.h"
 
 namespace __sanitizer {
 
+// The following is defined in a separate compilation unit to avoid pulling in
+// sanitizer_errno.h in this header, which leads to conflicts when other system
+// headers include errno.h. This is usually the result of an unlikely event,
+// and as such we do not care as much about having it inlined.
+void SetErrnoToENOMEM();
+
 // A common errno setting logic shared by almost all sanitizer allocator APIs.
 INLINE void *SetErrnoOnNull(void *ptr) {
   if (UNLIKELY(!ptr))
-    errno = errno_ENOMEM;
+    SetErrnoToENOMEM();
   return ptr;
 }
 
 // In case of the check failure, the caller of the following Check... functions
 // should "return POLICY::OnBadRequest();" where POLICY is the current allocator
 // failure handling policy.
 
 // Checks aligned_alloc() parameters, verifies that the alignment is a power of

lib/sanitizer_common/sanitizer_allocator_checks.cc

+//===-- sanitizer_allocator_checks.cc ---------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+/// Common allocator checks functions that need to be in a separate compilation
+/// unit.
+//
+//===----------------------------------------------------------------------===//
+
+#include "sanitizer_errno.h"
+
+namespace __sanitizer {
+
+void SetErrnoToENOMEM() {
+  errno = errno_ENOMEM;
+}
+
+} // namespace __sanitizer