Use -std=gnu11 for C

CMakeLists.txt

@@ -86,8 +86,8 @@ target_link_libraries( ${PROJECT_NAME} PRIVATE ${JULIA_LIBRARY} MPI::MPI_C )
 # Set appropriate compile flags
 target_compile_options( ${PROJECT_NAME} PUBLIC "-fPIC" )
 target_compile_options( ${PROJECT_NAME} PRIVATE -Wall -Wextra -Werror)
-# Require C11 standard for C files
-target_compile_options( ${PROJECT_NAME} PRIVATE $<$<COMPILE_LANGUAGE:C>:-std=c11>)
+# Require C11 standard with GNU extensions for C files
+target_compile_options( ${PROJECT_NAME} PRIVATE $<$<COMPILE_LANGUAGE:C>:-std=gnu11>)
 # Require Fortran 2018 standard for Fortran files
 target_compile_options( ${PROJECT_NAME} PRIVATE $<$<COMPILE_LANGUAGE:Fortran>:-std=f2018>)
 

src/auxiliary.c

@@ -1,22 +1,9 @@
-// Include first since it includes julia.h, for which we do not want to mess with the
-// macro definitions
-#include "auxiliary.h"
-
-// Enable support for `setenv`
-#ifdef _POSIX_C_SOURCE
-#undef _POSIX_C_SOURCE
-#endif
-#define _POSIX_C_SOURCE 200112L
-
-// Enable support for `realpath`
-#ifndef _DEFAULT_SOURCE
-#define _DEFAULT_SOURCE
-#endif
-
 #include <limits.h>
 #include <stdio.h>
 #include <stdlib.h>
 
+#include "auxiliary.h"
+
 
 // Default depot path *relative* to the project directory
 // OBS! If you change the value here, you should also update the default value of