diff --git a/opennurbs_defines.cpp b/opennurbs_defines.cpp
index 92d97fb1..dfc1af6b 100644
--- a/opennurbs_defines.cpp
+++ b/opennurbs_defines.cpp
@@ -503,7 +503,7 @@ int ON::CloseAllFiles()
   //fcloseall is not supported on OS X
   return EOF;
 #elif defined(ON_COMPILER_GNU)
-#error TODO - call gcc fcloseall()
+  fcloseall();
 #else
   // I can't find an fcloseall() or _fcloseall() in
   // gcc version egcs-2.91.66 19990314/Linux (egcs-1.1.2 release)
diff --git a/opennurbs_file_utilities.cpp b/opennurbs_file_utilities.cpp
index 4776529d..b790efdc 100644
--- a/opennurbs_file_utilities.cpp
+++ b/opennurbs_file_utilities.cpp
@@ -2739,7 +2739,7 @@ ON__UINT64 ON_SecondsSinceJanOne1970UTC()
   __time64_t t = _time64(nullptr);
   return (ON__UINT64)t;  
 
-#elif defined(ON_COMPILER_CLANG)
+#elif defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
 
   //__time64_t t = _time64(nullptr);
   time_t t = time(nullptr);
@@ -2779,7 +2779,7 @@ const ON_wString SecondsSinceJanOne1970UTCToString(
     sec = uct.tm_sec;
   }
 
-#elif defined(ON_COMPILER_CLANG)
+#elif defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
 
   const time_t t = (time_t)seconds_since_epoch;
   const struct tm* ptr = gmtime( &t );
diff --git a/opennurbs_locale.cpp b/opennurbs_locale.cpp
index effb512b..45c46a5b 100644
--- a/opennurbs_locale.cpp
+++ b/opennurbs_locale.cpp
@@ -1324,7 +1324,7 @@ public:
 
   static bool Validate_sprintf_s()
   {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG)  || defined(ON_COMPILER_GNU)
     // Test formatted printing
     char buffer[64] = { 0 };
     size_t buffer_capacity = (sizeof(buffer) / sizeof(buffer[0])) - 1;
@@ -1343,7 +1343,7 @@ public:
 
   static bool Validate_sprintf_l()
   {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted printing
     char buffer[64] = { 0 };
@@ -1368,7 +1368,7 @@ public:
 
   static bool Validate_sprintf_s_l()
   {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted printing
     char buffer[64] = { 0 };
@@ -1405,7 +1405,7 @@ public:
 
   static bool Validate_sscanf_s()
   {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
     // Test formatted scanning
     double a = ON_UNSET_VALUE;
     // Testing C-runtime - do not using ON_String::Scan
@@ -1422,7 +1422,7 @@ public:
 
   static bool Validate_sscanf_l()
   {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted scanning
     double a = ON_UNSET_VALUE;
@@ -1447,7 +1447,7 @@ public:
 
   static bool Validate_sscanf_s_l()
   {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
     // Test formatted scanning
     double a = ON_UNSET_VALUE;
@@ -1602,7 +1602,7 @@ bool ON_Locale::SetPeriodAsCRuntimeDecimalPoint()
     if (prev_type != _DISABLE_PER_THREAD_LOCALE && prev_type >= 0)
       _configthreadlocale(prev_type);
 
-#elif defined(ON_COMPILER_CLANG)
+#elif defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
     // Apple's Clang compiler
     const char* s = setlocale(LC_NUMERIC, "C");
     rc = (0 != s && 'C' == s[0] && 0 == s[1]);
diff --git a/opennurbs_string_format.cpp b/opennurbs_string_format.cpp
index bac30138..805be8d7 100644
--- a/opennurbs_string_format.cpp
+++ b/opennurbs_string_format.cpp
@@ -803,7 +803,7 @@ int ON_String::FormatVargsIntoBuffer(
   if (0 == buffer || buffer_capacity <= 0)
     return -1;
   buffer[0] = 0;
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
   // CLang modifies args so a copy is required
   va_list args_copy;
   va_copy (args_copy, args);
@@ -854,7 +854,7 @@ int ON_String::FormatVargsOutputCount(
   if ( nullptr == format || 0 == format[0] )
     return 0;
 
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_COMPILER_GNU)
   // CLang modifies args so a copy is required
   va_list args_copy;
   va_copy (args_copy, args);
@@ -1075,10 +1075,18 @@ int ON_wString::FormatVargsIntoBuffer(
   int len = vswprintf(buffer, buffer_capacity, format, args_copy);
   va_end(args_copy);
   
+#else
+
+#if defined(ON_COMPILER_GNU)
+  va_list args_copy;
+  va_copy (args_copy, args);
+  int len = vswprintf(buffer, buffer_capacity, format, args_copy);
+  va_end(args_copy);
 #else
   // Using ON_Locale::Ordinal.NumericLocalePtr() insures that a period 
   // will be use for the decimal point in formatted printing.
   int len = _vswprintf_p_l(buffer, buffer_capacity, format, ON_Locale::Ordinal.NumericLocalePtr(), args);
+#endif
 #endif
   if (((size_t)len) >= buffer_capacity)
     len = -1;
@@ -1214,9 +1222,38 @@ int ON_wString::FormatVargsOutputCount(
       break;
   }
   return -1;
+#else
+#if defined(ON_COMPILER_GNU)
+  wchar_t stack_buffer[1024];
+  ON_wStringBuffer buffer(stack_buffer, sizeof(stack_buffer) / sizeof(stack_buffer[0]));
+  size_t buffer_capacity = buffer.m_buffer_capacity;
+  for(;;)
+  {
+    va_list args_copy;
+    va_copy(args_copy, args);
+
+    const int formatted_string_count = vswprintf(buffer.m_buffer, buffer.m_buffer_capacity, format, args_copy);
+    va_end(args_copy);
+    if (formatted_string_count >= 0)
+    {
+      // formatted_string_count = number of wchar_t elements not including null terminator
+      return formatted_string_count;
+    }
+    if ( buffer_capacity >= 1024*16*16*16 )
+      break;
+    buffer_capacity *= 16;
+    if (false == buffer.GrowBuffer(buffer_capacity))
+      break;
+    if (nullptr == buffer.m_buffer)
+      break;
+    if (buffer_capacity < buffer.m_buffer_capacity)
+      break;
+  }
+  return -1;
 #else
   // Using ON_Locale::Ordinal.NumericLocalePtr() insures that a period 
   // will be use for the decimal point in formatted printing.
   return _vscwprintf_p_l(format, ON_Locale::Ordinal.NumericLocalePtr(), args);
 #endif
+#endif
 }
diff --git a/opennurbs_string_scan.cpp b/opennurbs_string_scan.cpp
index 652120de..539d95d4 100644
--- a/opennurbs_string_scan.cpp
+++ b/opennurbs_string_scan.cpp
@@ -85,7 +85,7 @@ int ON_String::ScanBufferVargs(
   va_list args
   )
 {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (nullptr == buffer || nullptr == format)
     return -1;
@@ -148,7 +148,7 @@ int ON_wString::ScanBufferVargs(
   va_list args
   )
 {
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (nullptr == buffer || nullptr == format)
     return -1;
@@ -397,7 +397,7 @@ const char* ON_String::ToNumber(
   local_buffer[local_buffer_count++] = 0;
 
   double x = value_on_failure;
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (1 == sscanf(local_buffer, "%lg", &x))
   {
@@ -639,7 +639,7 @@ const wchar_t* ON_wString::ToNumber(
   local_buffer[local_buffer_count++] = 0;
 
   double x = value_on_failure;
-#if defined(ON_COMPILER_CLANG)
+#if defined(ON_COMPILER_CLANG) || defined(ON_RUNTIME_LINUX)
 #if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
   if (1 == sscanf(local_buffer, "%lg", &x))
   {
diff --git a/opennurbs_subd_heap.cpp b/opennurbs_subd_heap.cpp
index 47d31a1a..00856d06 100644
--- a/opennurbs_subd_heap.cpp
+++ b/opennurbs_subd_heap.cpp
@@ -660,7 +660,7 @@ bool ON_SubD_FixedSizeHeap::ReturnPtrArray(
     m_p_index -= capacity;
     return true;
   }
-  return ON_SUBD_RETURN_ERROR(nullptr);
+  return ON_SUBD_RETURN_ERROR(false);
 }
 
 
@@ -1388,4 +1388,3 @@ void ON_SubDHeap::ReturnArray(
   }
   return;
 }
-
diff --git a/opennurbs_system.h b/opennurbs_system.h
index e2ff70a5..b9e4951a 100644
--- a/opennurbs_system.h
+++ b/opennurbs_system.h
@@ -540,7 +540,7 @@ typedef ON__UINT32 wchar_t;
 #pragma ON_PRAGMA_WARNING_AFTER_DIRTY_INCLUDE
 
 #pragma ON_PRAGMA_WARNING_BEFORE_DIRTY_INCLUDE
-#if defined(ON_RUNTIME_ANDROID)
+#if defined(ON_RUNTIME_ANDROID) || defined(ON_RUNTIME_LINUX)
 #include "android_uuid/uuid.h"
 #else
 #include <uuid/uuid.h>
diff --git a/opennurbs_uuid.cpp b/opennurbs_uuid.cpp
index 44f75a65..cb5bced4 100644
--- a/opennurbs_uuid.cpp
+++ b/opennurbs_uuid.cpp
@@ -15,7 +15,9 @@
 */
 
 #include "opennurbs.h"
-
+#if defined(ON_RUNTIME_LINUX)
+#include "android_uuid/uuid.h"
+#endif
 #if !defined(ON_COMPILING_OPENNURBS)
 // This check is included in all opennurbs source .c and .cpp files to insure
 // ON_COMPILING_OPENNURBS is defined when opennurbs source is compiled.
@@ -221,6 +223,12 @@ bool ON_CreateUuid( ON_UUID& new_uuid )
 
   return true;
 #else
+
+#if defined(ON_RUNTIME_LINUX)
+  uuid_generate((unsigned char*)&new_uuid);
+  return true;
+#else
+
   // You must supply a way to create unique ids or you 
   // will not be able to write 3dm files.
 #error TODO - generate uuid
@@ -228,6 +236,7 @@ bool ON_CreateUuid( ON_UUID& new_uuid )
   return false;
 #endif
 
+#endif
 #endif
 }