[lsan] [NFC] Change ARRAY_SIZE to internal_strnlen

[george.karpenkov]

Summary

Calling ARRAY_SIZE on a char* will not actually compute it's size, but just the pointer size.
A new Clang warning enables by default warns about this.

Replaced the call with internal_strnlen.

[fjricci]

lgtm - thanks!

[george.karpenkov]

@fjricci Now the test is actually failing, because the size of e.g. "__objc_classlist" is 16, and kMaxSegName is also 16. I'm changing < to <=, and adding +1 to the second strnlen arguments.
(unless there are any objections)

[fjricci]

I think that should be fine?

compiler-rt/lib/lsan/lsan_common_mac.cc

 //=-- lsan_common_mac.cc --------------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of LeakSanitizer.
 // Implementation of common leak checking functionality. Darwin-specific code.
 //
 //===----------------------------------------------------------------------===//
 
 #include "sanitizer_common/sanitizer_platform.h"
+#include "sanitizer_common/sanitizer_libc.h"
 #include "lsan_common.h"
 
 #if CAN_SANITIZE_LEAKS && SANITIZER_MAC
 
 #include "sanitizer_common/sanitizer_allocator_internal.h"
 #include "lsan_allocator.h"
 
 #include <pthread.h>

 static const char *kSkippedSecNames[] = {
     "__cfstring",       "__la_symbol_ptr",  "__mod_init_func",
     "__mod_term_func",  "__nl_symbol_ptr",  "__objc_classlist",
     "__objc_classrefs", "__objc_imageinfo", "__objc_nlclslist",
     "__objc_protolist", "__objc_selrefs",   "__objc_superrefs"};
 
 // Scans global variables for heap pointers.
 void ProcessGlobalRegions(Frontier *frontier) {
-  for (auto name : kSkippedSecNames) CHECK(ARRAY_SIZE(name) < kMaxSegName);
+  for (auto name : kSkippedSecNames)
+    CHECK(internal_strnlen(name, kMaxSegName) < kMaxSegName);
 
   MemoryMappingLayout memory_mapping(false);
   InternalMmapVector<LoadedModule> modules;
   modules.reserve(128);
   memory_mapping.DumpListOfModules(&modules);
   for (uptr i = 0; i < modules.size(); ++i) {
     // Even when global scanning is disabled, we still need to scan
     // system libraries for stashed pointers