4 files changed, 25 insertions, 11 deletions
diff --git a/absl/base/attributes.h b/absl/base/attributes.h
index c44b8828..291ad89e 100644
--- a/absl/base/attributes.h
+++ b/absl/base/attributes.h
@@ -402,17 +402,28 @@
 
 // ABSL_MUST_USE_RESULT
 //
-// Tells the compiler to warn about unused return values for functions declared
-// with this macro. The macro must appear as the very first part of a function
-// declaration or definition:
+// Tells the compiler to warn about unused results.
 //
-// Example:
+// When annotating a function, it must appear as the first part of the
+// declaration or definition. The compiler will warn if the return value from
+// such a function is unused:
 //
 //   ABSL_MUST_USE_RESULT Sprocket* AllocateSprocket();
+//   AllocateSprocket();  // Triggers a warning.
+//
+// When annotating a class, it is equivalent to annotating every function which
+// returns an instance.
+//
+//   class ABSL_MUST_USE_RESULT Sprocket {};
+//   Sprocket();  // Triggers a warning.
+//
+//   Sprocket MakeSprocket();
+//   MakeSprocket();  // Triggers a warning.
+//
+// Note that references and pointers are not instances:
 //
-// This placement has the broadest compatibility with GCC, Clang, and MSVC, with
-// both defs and decls, and with GCC-style attributes, MSVC declspec, C++11
-// and C++17 attributes.
+//   Sprocket* SprocketPointer();
+//   SprocketPointer();  // Does *not* trigger a warning.
 //
 // ABSL_MUST_USE_RESULT allows using cast-to-void to suppress the unused result
 // warning. For that, warn_unused_result is used only for clang but not for gcc.
diff --git a/absl/base/config.h b/absl/base/config.h
index e3edb2bf..ca089f6d 100644
--- a/absl/base/config.h
+++ b/absl/base/config.h
@@ -274,7 +274,8 @@
 #error ABSL_HAVE_MMAP cannot be directly set
 #elif defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) ||   \
     defined(__ros__) || defined(__native_client__) || defined(__asmjs__) || \
-    defined(__wasm__) || defined(__Fuchsia__) || defined(__sun)
+    defined(__wasm__) || defined(__Fuchsia__) || defined(__sun) || \
+    defined(__ASYLO__)
 #define ABSL_HAVE_MMAP 1
 #endif
 
@@ -328,6 +329,8 @@
 #define ABSL_HAVE_ALARM 1
 #elif defined(_MSC_VER)
 // feature tests for Microsoft's library
+#elif defined(__EMSCRIPTEN__)
+// emscripten doesn't support signals
 #elif defined(__native_client__)
 #else
 // other standard libraries
diff --git a/absl/base/internal/direct_mmap.h b/absl/base/internal/direct_mmap.h
index 0426e118..3e5368db 100644
--- a/absl/base/internal/direct_mmap.h
+++ b/absl/base/internal/direct_mmap.h
@@ -75,7 +75,7 @@ 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) {
-    pagesize = getpagesize();
+    pagesize = sysconf(_SC_PAGESIZE);
   }
   if (offset < 0 || offset % pagesize != 0) {
     errno = EINVAL;
diff --git a/absl/base/internal/low_level_alloc.cc b/absl/base/internal/low_level_alloc.cc
index 6e636a02..015edf8d 100644
--- a/absl/base/internal/low_level_alloc.cc
+++ b/absl/base/internal/low_level_alloc.cc
@@ -208,7 +208,7 @@ struct LowLevelAlloc::Arena {
   int32_t allocation_count GUARDED_BY(mu);
   // flags passed to NewArena
   const uint32_t flags;
-  // Result of getpagesize()
+  // Result of sysconf(_SC_PAGESIZE)
   const size_t pagesize;
   // Lowest power of two >= max(16, sizeof(AllocList))
   const size_t roundup;
@@ -325,7 +325,7 @@ size_t GetPageSize() {
   GetSystemInfo(&system_info);
   return std::max(system_info.dwPageSize, system_info.dwAllocationGranularity);
 #else
-  return getpagesize();
+  return sysconf(_SC_PAGESIZE);
 #endif
 }