improve checks for libatomic linking

This code piece is adapted from https://github.com/KDE/krita/blob/451e1415fd1b3a0f9c24de2fd4707d1b1e164236/cmake/modules/CheckAtomic.cmake#L23

Fixes: f502ccbc
Fixes: https://bugs.gentoo.org/828065Tested-by: Yixun Lan <dlan@gentoo.org>
Reviewed-by: Daniel Black

configure.cmake

@@ -891,9 +891,16 @@ HAVE_GCC_ATOMIC_BUILTINS)
 CHECK_CXX_SOURCE_COMPILES("
 int main()
 {
-  long long int var= 1;
-  long long int *ptr= &var;
-  return (int)__atomic_load_n(ptr, __ATOMIC_SEQ_CST);
+  char x=1;
+  short y=1;
+  int z=1;
+  long w = 1;
+  long long s = 1;
+  x = __atomic_add_fetch(&x, 1, __ATOMIC_SEQ_CST);
+  y = __atomic_add_fetch(&y, 1, __ATOMIC_SEQ_CST);
+  z = __atomic_add_fetch(&z, 1, __ATOMIC_SEQ_CST);
+  w = __atomic_add_fetch(&w, 1, __ATOMIC_SEQ_CST);
+  return (int)__atomic_load_n(&s, __ATOMIC_SEQ_CST);
 }"
 HAVE_GCC_C11_ATOMICS_WITHOUT_LIBATOMIC)
 IF (HAVE_GCC_C11_ATOMICS_WITHOUT_LIBATOMIC)
@@ -904,9 +911,16 @@ ELSE()
   CHECK_CXX_SOURCE_COMPILES("
   int main()
   {
-    long long int var= 1;
-    long long int *ptr= &var;
-    return (int)__atomic_load_n(ptr, __ATOMIC_SEQ_CST);
+    char x=1;
+    short y=1;
+    int z=1;
+    long w = 1;
+    long long s = 1;
+    x = __atomic_add_fetch(&x, 1, __ATOMIC_SEQ_CST);
+    y = __atomic_add_fetch(&y, 1, __ATOMIC_SEQ_CST);
+    z = __atomic_add_fetch(&z, 1, __ATOMIC_SEQ_CST);
+    w = __atomic_add_fetch(&w, 1, __ATOMIC_SEQ_CST);
+    return (int)__atomic_load_n(&s, __ATOMIC_SEQ_CST);
   }"
   HAVE_GCC_C11_ATOMICS_WITH_LIBATOMIC)
   IF(HAVE_GCC_C11_ATOMICS_WITH_LIBATOMIC)

storage/rocksdb/CMakeLists.txt

@@ -129,7 +129,8 @@ SET(ROCKSDB_SE_SOURCES
 # This is a strong requirement coming from RocksDB. No conditional checks here.
 #ADD_DEFINITIONS(-DROCKSDB_PLATFORM_POSIX -DROCKSDB_LIB_IO_POSIX
 #)
-if(CMAKE_SYSTEM_PROCESSOR STREQUAL "riscv64")
+
+if (HAVE_GCC_C11_ATOMICS_WITH_LIBATOMIC)
   SET(ATOMIC_EXTRA_LIBS -latomic)
 else()
   SET(ATOMIC_EXTRA_LIBS)