fixes #1225 atomic check operation fails with android cross toolchain

2 files changed, 9 insertions, 77 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 10185c8e..2b78d4e0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -155,13 +155,6 @@ if (NOT NNG_SANITIZER STREQUAL "none")
     set(NNG_SANITIZER_FLAGS "-fsanitize=${NNG_SANITIZER}")
 endif ()
 
-include(CheckAtomicLib)
-CheckAtomicLib()
-if (NOT HAVE_C_ATOMICS_WITHOUT_LIB AND HAVE_C_ATOMICS_WITH_LIB)
-    list(APPEND NNG_LIBS "atomic")
-endif ()
-
-
 if (NNG_ENABLE_COVERAGE)
     # NB: This only works for GCC and Clang 3.0 and newer.  If your stuff
     # is older than that, you will need to find something newer.  For
@@ -327,6 +320,15 @@ else ()
     nng_check_lib(nsl gethostbyname NNG_HAVE_LIBNSL)
     nng_check_lib(socket socket NNG_HAVE_LIBSOCKET)
 
+    # GCC needs libatomic on some architectures (e.g. ARM) because the
+    # underlying architecture may lack the necessary atomic primitives.
+    # One hopes that the libatomic implementation is superior to just using
+    # a pthread mutex.  The symbol chosen here was identified from GCC's
+    # libatomic map file.
+    #
+    # Arguably when using clang, compiler-rt might be better.
+    nng_check_lib(__atomic_load_1 atomic NNG_HAVE_LIBATOMIC)
+
     nng_check_sym(AF_UNIX sys/socket.h NNG_HAVE_UNIX_SOCKETS)
     nng_check_sym(backtrace_symbols_fd execinfo.h NNG_HAVE_BACKTRACE)
     nng_check_struct_member(msghdr msg_control sys/socket.h NNG_HAVE_MSG_CONTROL)
diff --git a/cmake/CheckAtomicLib.cmake b/cmake/CheckAtomicLib.cmake
deleted file mode 100644
index 06979305..00000000
--- a/cmake/CheckAtomicLib.cmake
+++ /dev/null
@@ -1,70 +0,0 @@
-#
-# Copyright 2020 Kenneth Haase <kh@beingmeta.com>
-#
-# This software is supplied under the terms of the MIT License, a
-# copy of which should be located in the distribution where this
-# file was obtained (LICENSE.txt).  A copy of the license may also be
-# found online at https://opensource.org/licenses/MIT.
-#
-
-# atomic builtins are required for threading support.
-
-INCLUDE(CheckIncludeFiles)
-INCLUDE(CheckCSourceCompiles)
-INCLUDE(CheckLibraryExists)
-
-# Sometimes linking against libatomic is required for atomic ops, if
-# the platform doesn't support lock-free atomics.
-
-function(check_c_atomics_without_lib varname)
-  CHECK_C_SOURCE_COMPILES("
-#include <stdatomic.h>
-int main() {
-  _Atomic long long x;
-  atomic_store(&x,3);
-  long long y = atomic_load(&x);
-  atomic_fetch_add(&x,12);
-  long long z = atomic_load(&x);
-  
-  return x;
-}
-" ${varname})
-endfunction(check_c_atomics_without_lib)
-
-function(check_c_atomics_with_lib varname)
-  SET(SAVED_CMAKE_REQUIRED_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
-  list(APPEND CMAKE_REQUIRED_LIBRARIES "atomic")
-  CHECK_C_SOURCE_COMPILES("
-#include <stdatomic.h>
-int main() {
-  _Atomic long long x;
-  atomic_store(&x,3);
-  long long y = atomic_load(&x);
-  atomic_fetch_add(&x,12);
-  long long z = atomic_load(&x);
-  
-  return x;
-}
-" ${varname})
-  SET(CMAKE_REQUIRED_LIBRARIES "${SAVED_CMAKE_REQUIRED_LIBRARIES}")
-endfunction(check_c_atomics_with_lib)
-
-macro (CheckAtomicLib)
-  # First check if atomics work without the library.
-  if(MSVC)
-    set(HAVE_C_ATOMICS_WITHOUT_LIB True)
-  else()
-    check_c_atomics_without_lib(HAVE_C_ATOMICS_WITHOUT_LIB)
-    if(NOT HAVE_C_ATOMICS_WITHOUT_LIB)
-      check_library_exists(atomic __atomic_fetch_add_8 "" HAVE_LIBATOMIC)
-      if( HAVE_LIBATOMIC )
-	check_c_atomics_with_lib(HAVE_C_ATOMICS_WITH_LIB)
-	if (NOT HAVE_C_ATOMICS_WITH_LIB)
-	  message(FATAL_ERROR "Host compiler must support atomic types!")
-	endif()
-      else()
-	message(FATAL_ERROR "Host compiler appears to require libatomic, but cannot find it.")
-      endif()
-    endif()
-  endif()
-endmacro (CheckAtomicLib)