Export of internal Abseil changes.

--
5278e56bd7d322ecf161eaf29fd7fa3941d7431b by Greg Falcon <gfalcon@google.com>:

internal change

PiperOrigin-RevId: 222078614
GitOrigin-RevId: 5278e56bd7d322ecf161eaf29fd7fa3941d7431b
Change-Id: I1e86bef2e3733c81148a1a42dccd8182fe3f7fae

absl/base/internal/direct_mmap.h

@@ -75,7 +75,11 @@ inline void* DirectMmap(void* start, size_t length, int prot, int flags, int fd,
   // On these architectures, implement mmap with mmap2.
   static int pagesize = 0;
   if (pagesize == 0) {
+#if defined(__wasm__) || defined(__asmjs__)
+    pagesize = getpagesize();
+#else
     pagesize = sysconf(_SC_PAGESIZE);
+#endif
   }
   if (offset < 0 || offset % pagesize != 0) {
     errno = EINVAL;

absl/base/internal/low_level_alloc.cc

@@ -324,6 +324,8 @@ size_t GetPageSize() {
   SYSTEM_INFO system_info;
   GetSystemInfo(&system_info);
   return std::max(system_info.dwPageSize, system_info.dwAllocationGranularity);
+#elif defined(__wasm__) || defined(__asmjs__)
+  return getpagesize();
 #else
   return sysconf(_SC_PAGESIZE);
 #endif

absl/debugging/failure_signal_handler.cc

@@ -119,7 +119,11 @@ const char* FailureSignalToString(int signo) {
 #ifndef _WIN32
 
 static bool SetupAlternateStackOnce() {
+#if defined(__wasm__) || defined (__asjms__)
+  const size_t page_mask = getpagesize() - 1;
+#else
   const size_t page_mask = sysconf(_SC_PAGESIZE) - 1;
+#endif
   size_t stack_size = (std::max(SIGSTKSZ, 65536) + page_mask) & ~page_mask;
 #if defined(ADDRESS_SANITIZER) || defined(MEMORY_SANITIZER) || \
     defined(THREAD_SANITIZER)

absl/debugging/symbolize_elf.inc

@@ -333,7 +333,11 @@ static std::atomic<Symbolizer *> g_cached_symbolizer;
 }  // namespace
 
 static int SymbolizerSize() {
+#if defined(__wasm__) || defined(__asmjs__)
+  int pagesize = getpagesize();
+#else
   int pagesize = sysconf(_SC_PAGESIZE);
+#endif
   return ((sizeof(Symbolizer) - 1) / pagesize + 1) * pagesize;
 }