accomodate GCC < 10

Author: scivision

cmake/compilers.cmake

@@ -170,6 +170,9 @@ add_compile_options(
 "$<$<AND:$<COMPILE_LANGUAGE:Fortran>,$<CONFIG:Release>>:-fno-backtrace>"
 )
 
+add_compile_options("$<$<AND:$<COMPILE_LANGUAGE:CXX>,$<VERSION_LESS:$<CXX_COMPILER_VERSION>,10.0>>:-Wno-attributes>")
+# this is for UNLIKELY/LIKELY macros
+
 # "$<$<COMPILE_LANGUAGE:Fortran>:-Werror=array-bounds;-fcheck=all>"
 
 elseif(CMAKE_Fortran_COMPILER_ID MATCHES "^Intel")

src/uid/uid.cpp

@@ -18,6 +18,12 @@
 
 #include "uid.h"
 
+#if __has_attribute(unlikely)
+#define UNLIKELY [[unlikely]]
+#else
+#define UNLIKELY
+#endif
+
 
 extern "C" {
 std::string::size_type c_get_uid(char* result, const std::string::size_type buffer_size) {
@@ -27,7 +33,7 @@ std::string::size_type c_get_uid(char* result, const std::string::size_type buff
 
 std::string::size_type str2char(std::string_view s, char* result, const std::string::size_type buffer_size)
 {
-  if(s.length() >= buffer_size) [[unlikely]]
+  if(s.length() >= buffer_size) UNLIKELY
   {
     std::cerr << "ERROR: " << s << " " << std::make_error_code(std::errc::result_out_of_range) << "\n";
     return 0;