Removed `#define _POSIX_C_SOURCE`s where `#define _GNU_SOURCE` was also defined, as `_GNU_SOURCE` implicitly defines `_POSIX_C_SOURCE`, but on BSD/macOS, `_POSIX_C_SOURCE` prevents non-POSIX extensions from being defined.
diff --git a/src/cbortojson.c b/src/cbortojson.c
index 856d926..fff9d29 100644
--- a/src/cbortojson.c
+++ b/src/cbortojson.c
@@ -25,7 +25,6 @@
 #define _BSD_SOURCE 1
 #define _DEFAULT_SOURCE 1
 #define _GNU_SOURCE 1
-#define _POSIX_C_SOURCE 200809L
 #ifndef __STDC_LIMIT_MACROS
 #  define __STDC_LIMIT_MACROS 1
 #endif
diff --git a/tools/json2cbor/json2cbor.c b/tools/json2cbor/json2cbor.c
index c13a751..26e80fc 100644
--- a/tools/json2cbor/json2cbor.c
+++ b/tools/json2cbor/json2cbor.c
@@ -22,7 +22,6 @@
 **
 ****************************************************************************/
 
-#define _POSIX_C_SOURCE 200809L
 #define _GNU_SOURCE
 #include "cbor.h"
 #include "cborinternal_p.h"