diff --git a/include/novas.h b/include/novas.h
index 6e2a0e81..d09509e3 100644
--- a/include/novas.h
+++ b/include/novas.h
@@ -1704,7 +1704,7 @@ int mod_to_gcrs(double jd_tdb, const double *in, double *out);
 #  ifndef THREAD_LOCAL
 #    if __STDC_VERSION__ >= 201112L
 #      define THREAD_LOCAL _Thread_local          ///< C11 standard for thread-local variables
-#    elif __GNUC__ >= 3 && __GNUC_MINOR__ >= 3
+#    elif __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 3)
 #      define THREAD_LOCAL __thread               ///< pre C11 gcc >= 3.3 standard for thread-local variables
 #    else
 #      define THREAD_LOCAL                        ///< no thread-local variables
diff --git a/src/novas.c b/src/novas.c
index 12303689..3a23551c 100644
--- a/src/novas.c
+++ b/src/novas.c
@@ -43,6 +43,9 @@
 #define C2                  (C * C)   ///< [m<sup>2</sup>/s<sup>2</sup>] Speed of light squared
 #define EPREC               1e-12     ///< Required precision for eccentric anomaly in orbital calculation
 
+/// [bytes] Sizeof binary CIO locator file header
+#define CIO_BIN_HEADER_SIZE   (3*sizeof(double) + sizeof(long))
+
 // <---------- GLOBAL VARIABLES -------------->
 
 #if !DEFAULT_SOLSYS
@@ -5492,13 +5495,15 @@ short cio_array(double jd_tdb, long n_pts, ra_of_cio *cio) {
   static const char *fn = "cio_array";
 
   // Packed struct in case long is not the same width a double
-  struct __attribute__ ((packed)) cio_file_header {
+  struct cio_file_header {
     double jd_start;
     double jd_end;
     double jd_interval;
     long n_recs;
   };
 
+
+
   static const FILE *last_file;
   static struct cio_file_header lookup;
   static ra_of_cio cache[NOVAS_CIO_CACHE_SIZE];
@@ -5555,13 +5560,13 @@ short cio_array(double jd_tdb, long n_pts, ra_of_cio *cio) {
     }
     else {
       is_ascii = 0;
-      header_size = sizeof(struct cio_file_header);
+      header_size = CIO_BIN_HEADER_SIZE;
       lrec = sizeof(ra_of_cio);
 
       fseek(cio_file, 0, SEEK_SET);
 
       // Read the file header
-      if(fread(&lookup, sizeof(struct cio_file_header), 1, cio_file) != 1)
+      if(fread(&lookup, header_size, 1, cio_file) != 1)
         return novas_error(-1, errno, fn, "incomplete or corrupted binary CIO locator data header: %s", strerror(errno));
     }
 
diff --git a/src/super.c b/src/super.c
index f3c98d95..71f2594c 100644
--- a/src/super.c
+++ b/src/super.c
@@ -10,8 +10,10 @@
 
 // We'll use gcc major version as a proxy for the glibc library to decide which feature macro to use.
 // gcc 5.1 was released 2015-04-22...
-#if __GNUC__ >= 5
-#  define _DEFAULT_SOURCE         ///< strcasdecmp() feature macro starting glibc 2.20 (2014-09-08)
+#ifndef __GNUC__
+#  define _DEFAULT_SOURCE         ///< strcasecmp() feature macro starting glibc 2.20 (2014-09-08)
+#elif __GNUC__ >= 5 || __clang__
+#  define _DEFAULT_SOURCE         ///< strcasecmp() feature macro starting glibc 2.20 (2014-09-08)
 #else
 #  define _BSD_SOURCE             ///< strcasecmp() feature macro for glibc <= 2.19
 #endif
diff --git a/test/src/test-super.c b/test/src/test-super.c
index 8a4ca871..82168717 100644
--- a/test/src/test-super.c
+++ b/test/src/test-super.c
@@ -8,7 +8,7 @@
 
 // We'll use gcc major version as a proxy for the glibc library to decide which feature macro to use.
 // gcc 5.1 was released 2015-04-22...
-#if __GNUC__ >= 5
+#if __GNUC__ >= 5 || __clang__
 #  define _DEFAULT_SOURCE        ///< strcasdecmp() feature macro starting glibc 2.20 (2014-09-08)
 #else
 #  define _BSD_SOURCE           ///< strcasecmp() feature macro for glibc <= 2.19