diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0898222ff81..e5bf28848c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -39,6 +39,17 @@ if( ${TARGET_OS} STREQUAL "Linux" )
     message("Unsupported architecture: ${TARGET_ARCHITECTURE}" )
     return()
   endif()
+elseif( ${TARGET_OS} STREQUAL "Darwin" )
+  set(OS "OSX")
+  set(OSNAME "Darwin")
+  if( ${TARGET_ARCHITECTURE} STREQUAL "x86_64" )
+    set(ARCHNAME x86-64)
+    set(ARCH X86)
+    set(WRDSZ 64)
+  else()
+    message("Unsupported architecture: ${TARGET_ARCHITECTURE}" )
+    return()
+  endif()
 else()
   message("Unsupported OS: ${TARGET_OS}" )
   return()
diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 33dc89b848b..24d809a3382 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -6,13 +6,24 @@
 
 set (RUNTIME_SHARED_DIR ${CMAKE_CURRENT_SOURCE_DIR}/shared)
 
+if( ${TARGET_OS} STREQUAL "Darwin" )
+  add_definitions(
+   -DTARGET_OSX
+   -DTARGET_OSX_X8664
+   -DOSX86
+  )
+else()
+  add_definitions(
+   -DTARGET_LINUX
+   -DLINUX
+  )
+endif()
+
 add_definitions(
  -DMAXCPUS=256 
  -DMAXCPUSL=8 
  -DMAXCPUSR=8 
- -DTARGET_LINUX 
  -DTARGET_LLVM 
- -DLINUX 
  -DPGF90 
  -DPGFLANG
  -DNATIVE_FPCVT
diff --git a/runtime/flang/CMakeLists.txt b/runtime/flang/CMakeLists.txt
index 9ea054255e3..021b757f06e 100644
--- a/runtime/flang/CMakeLists.txt
+++ b/runtime/flang/CMakeLists.txt
@@ -500,9 +500,14 @@ set_property(TARGET flang_shared PROPERTY OUTPUT_NAME flang)
 #
 add_dependencies(flang_shared flang_static)
 
-target_link_libraries(flang_shared ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib/libflangrti.so)
-# Resolve symbols against libm and librt
-target_link_libraries(flang_shared m rt)
+if( ${TARGET_OS} STREQUAL "Darwin" )
+  target_link_libraries(flang_shared ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib/libflangrti.dylib)
+  target_link_libraries(flang_shared m pgmath omp)
+else()
+  target_link_libraries(flang_shared ${CMAKE_BINARY_DIR}/${CMAKE_CFG_INTDIR}/lib/libflangrti.so)
+  # Resolve symbols against libm and librt
+  target_link_libraries(flang_shared m rt)
+endif()
 
 set(SHARED_LIBRARY FALSE)
 
diff --git a/runtime/flang/global.h b/runtime/flang/global.h
index 3157ce4b442..7f1743229d6 100644
--- a/runtime/flang/global.h
+++ b/runtime/flang/global.h
@@ -76,7 +76,6 @@ typedef char sbool; /* short boolean (for use in large structs) */
 #define assert(ex)
 #endif
 
-extern char *strcpy();
 #define STASH(str) (strcpy((char *)malloc(strlen(str) + 1), str))
 
 /* defs used by __fortio_error */
diff --git a/runtime/flang/stime3f.c b/runtime/flang/stime3f.c
index d8a58f9ad89..f236640063e 100644
--- a/runtime/flang/stime3f.c
+++ b/runtime/flang/stime3f.c
@@ -17,6 +17,10 @@
 
 int ENT3F(STIME, stime)(int *tp)
 {
+#ifdef TARGET_OSX
+  /* stime() doesn't exist on maxOS and is root-only anyway */
+  return EPERM;
+#else
   int i;
   struct timespec ts = {0};
 
@@ -25,6 +29,7 @@ int ENT3F(STIME, stime)(int *tp)
     i = __io_errno();
 
   return i;
+#endif
 }
 
 #endif /* !WINNT */
diff --git a/runtime/flangrti/CMakeLists.txt b/runtime/flangrti/CMakeLists.txt
index 97fe566302c..f21f5ca13b0 100644
--- a/runtime/flangrti/CMakeLists.txt
+++ b/runtime/flangrti/CMakeLists.txt
@@ -82,14 +82,14 @@ target_link_libraries(flangrti_shared m)
 if (NOT DEFINED LIBOMP_EXPORT_DIR)
   find_library( 
     FLANG_LIBOMP
-    libomp.so
+    libomp${CMAKE_SHARED_LIBRARY_SUFFIX}
     HINTS ${CMAKE_BINARY_DIR}/lib)
   target_link_libraries(flangrti_shared ${FLANG_LIBOMP})
 endif()
 
 find_library( 
   LIBPGMATH
-  libpgmath.so
+  libpgmath${CMAKE_SHARED_LIBRARY_SUFFIX}
   HINTS ${CMAKE_BINARY_DIR}/lib)
 target_link_libraries(flangrti_shared ${LIBPGMATH})
 
diff --git a/runtime/flangrti/dumpregs.h b/runtime/flangrti/dumpregs.h
index 31c07feb51e..77ba95edc86 100644
--- a/runtime/flangrti/dumpregs.h
+++ b/runtime/flangrti/dumpregs.h
@@ -10,7 +10,11 @@
  *  \file
  *  Declare routines that access the machine registers
  */
-
+#if defined(TARGET_OSX) || defined(TARGET_WIN)
+#define gregset_t void
+void dumpregs(void *);
+void *getRegs(void *);
+#else
 void dumpregs(gregset_t *regs);
 gregset_t *getRegs(ucontext_t *u);
-
+#endif
diff --git a/runtime/flangrti/iostdinit.c b/runtime/flangrti/iostdinit.c
index 378ae9a1e59..7c43122b03e 100644
--- a/runtime/flangrti/iostdinit.c
+++ b/runtime/flangrti/iostdinit.c
@@ -153,7 +153,7 @@ __io_ferror(void *p)
 int
 __io_getfd(void *fp)
 {
-  return (((FILE *)fp)->_fileno);
+  return fileno((FILE *)fp);
 }
 
 /* is a tty? */
diff --git a/runtime/flangrti/ktrap.c b/runtime/flangrti/ktrap.c
index c28debaef2b..573152d65bf 100644
--- a/runtime/flangrti/ktrap.c
+++ b/runtime/flangrti/ktrap.c
@@ -50,7 +50,11 @@ __ktrap(void)
         excepts |= FE_UNDERFLOW;
       if (bv & 0x100)
         excepts |= FE_INEXACT;
+#ifdef TARGET_OSX
+      __fenv_feenableexcept(excepts);
+#else
       feenableexcept(excepts);  /* glibc 2.2 extension to fenv.h */
+#endif
     }
   }
 }
diff --git a/runtime/flangrti/trace_lin.c b/runtime/flangrti/trace_lin.c
index 78b161c4dcd..32d3ce4c4d9 100644
--- a/runtime/flangrti/trace_lin.c
+++ b/runtime/flangrti/trace_lin.c
@@ -15,7 +15,11 @@
 #include <string.h>
 #include <sys/types.h>
 #include <unistd.h>
+#ifdef TARGET_OSX
+#include <limits.h>
+#else
 #include <linux/limits.h>
+#endif
 #include <inttypes.h>
 
 /* codes and strings for signals */
diff --git a/runtime/libpgmath/lib/common/dceil.c b/runtime/libpgmath/lib/common/dceil.c
index b1f8675e1d7..028b301ee5a 100644
--- a/runtime/libpgmath/lib/common/dceil.c
+++ b/runtime/libpgmath/lib/common/dceil.c
@@ -12,13 +12,13 @@
 
 #if     defined(__AVX__)
 double
-__mth_i_dceil_avx(double x)
+__mth_i_dceil(double x)
 {
   return _mm_cvtsd_f64(_mm_ceil_sd(_mm_set1_pd(x), _mm_set1_pd(x)));
 }
 #elif   defined(__SSE4_1__)
 double
-__mth_i_dceil_sse(double x)
+__mth_i_dceil(double x)
 {
   return _mm_cvtsd_f64(_mm_ceil_sd(_mm_set1_pd(x), _mm_set1_pd(x)));
 }
diff --git a/runtime/libpgmath/lib/common/dfloor.c b/runtime/libpgmath/lib/common/dfloor.c
index db5c54cbe0f..5e78e3d0c05 100644
--- a/runtime/libpgmath/lib/common/dfloor.c
+++ b/runtime/libpgmath/lib/common/dfloor.c
@@ -12,13 +12,13 @@
 
 #if     defined(__AVX__)
 double
-__mth_i_dfloor_avx(double x)
+__mth_i_dfloor(double x)
 {
   return _mm_cvtsd_f64(_mm_floor_sd(_mm_set1_pd(x), _mm_set1_pd(x)));
 }
 #elif   defined(__SSE4_1__)
 double
-__mth_i_dfloor_sse(double x)
+__mth_i_dfloor(double x)
 {
   return _mm_cvtsd_f64(_mm_floor_sd(_mm_set1_pd(x), _mm_set1_pd(x)));
 }
diff --git a/runtime/libpgmath/lib/common/floor.c b/runtime/libpgmath/lib/common/floor.c
index 6895671951f..1bd55a8d21c 100644
--- a/runtime/libpgmath/lib/common/floor.c
+++ b/runtime/libpgmath/lib/common/floor.c
@@ -12,13 +12,13 @@
 
 #if     defined(__AVX__)
 float
-__mth_i_floor_avx(float x)
+__mth_i_floor(float x)
 {
   return _mm_cvtss_f32(_mm_floor_ss(_mm_set1_ps(x), _mm_set1_ps(x)));
 }
 #elif   defined(__SSE4_1__)
 float
-__mth_i_floor_sse(float x)
+__mth_i_floor(float x)
 {
   return _mm_cvtss_f32(_mm_floor_ss(_mm_set1_ps(x), _mm_set1_ps(x)));
 }
diff --git a/tools/flang1/flang1exe/gbldefs.h b/tools/flang1/flang1exe/gbldefs.h
index 8b6efe40b96..ccb989b0c44 100644
--- a/tools/flang1/flang1exe/gbldefs.h
+++ b/tools/flang1/flang1exe/gbldefs.h
@@ -162,7 +162,6 @@ char *mkfname(char *, char *, char *); /* from miscutil.c: */
 bool is_xflag_bit(int);
 void set_xflag(int, INT);
 void set_yflag(int, INT);
-void bzero(void *, size_t);
 void list_init(FILE *); /* listing.c: */
 void list_line(char *); /* listing.c */
 void list_page(void);   /* listing.c */
diff --git a/tools/flang2/CMakeLists.txt b/tools/flang2/CMakeLists.txt
index 9a2dde76d01..75d99488aa7 100644
--- a/tools/flang2/CMakeLists.txt
+++ b/tools/flang2/CMakeLists.txt
@@ -23,7 +23,8 @@ set(FLANG2_INCLUDE_DIR    ${CMAKE_CURRENT_BINARY_DIR}/include)
 
 include_directories(${FLANG2_INCLUDE_DIR})
 
-if( ${TARGET_OS} STREQUAL "Linux" )
+# this is a hack until there is a proper setup
+if( ${TARGET_OS} STREQUAL "Linux|Darwin" )
   if( ${TARGET_ARCHITECTURE} STREQUAL "x86_64" )
     set(X86_64 ON)
     set(LINUX86 ON)
diff --git a/tools/flang2/flang2exe/x86_64-Darwin b/tools/flang2/flang2exe/x86_64-Darwin
new file mode 120000
index 00000000000..8073d31fcf2
--- /dev/null
+++ b/tools/flang2/flang2exe/x86_64-Darwin
@@ -0,0 +1 @@
+x86_64-Linux
\ No newline at end of file