diff --git a/core/c/libc/complex.odin b/core/c/libc/complex.odin
index e91d39023..62b28f0cd 100644
--- a/core/c/libc/complex.odin
+++ b/core/c/libc/complex.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
diff --git a/core/c/libc/ctype.odin b/core/c/libc/ctype.odin
index 9e4b31208..05d9dcd37 100644
--- a/core/c/libc/ctype.odin
+++ b/core/c/libc/ctype.odin
@@ -2,6 +2,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
diff --git a/core/c/libc/errno.odin b/core/c/libc/errno.odin
index dd17ce515..8ebe2f734 100644
--- a/core/c/libc/errno.odin
+++ b/core/c/libc/errno.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
@@ -38,6 +40,20 @@ when ODIN_OS == "windows" {
 	ERANGE :: 34
 }
 
+when ODIN_OS == "darwin" {
+	@(private="file")
+	@(default_calling_convention="c")
+	foreign libc {
+		@(link_name="__error")
+		_get_errno :: proc() -> ^int ---
+	}
+
+	// Unknown
+	EDOM   :: 33
+	EILSEQ :: 92
+	ERANGE :: 34
+}
+
 // Odin has no way to make an identifier "errno" behave as a function call to
 // read the value, or to produce an lvalue such that you can assign a different
 // error value to errno. To work around this, just expose it as a function like
diff --git a/core/c/libc/math.odin b/core/c/libc/math.odin
index c1c51fa25..ee702b82e 100644
--- a/core/c/libc/math.odin
+++ b/core/c/libc/math.odin
@@ -6,6 +6,8 @@ import "core:intrinsics"
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
diff --git a/core/c/libc/setjmp.odin b/core/c/libc/setjmp.odin
index 4f3ae3aa3..dcd4a9c64 100644
--- a/core/c/libc/setjmp.odin
+++ b/core/c/libc/setjmp.odin
@@ -4,10 +4,11 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
-
 when ODIN_OS == "windows" {
 	@(default_calling_convention="c")
 	foreign libc {
diff --git a/core/c/libc/signal.odin b/core/c/libc/signal.odin
index ad007287e..e1044dc02 100644
--- a/core/c/libc/signal.odin
+++ b/core/c/libc/signal.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
@@ -32,7 +34,20 @@ when ODIN_OS == "windows" {
 	SIGTERM :: 15
 }
 
-when ODIN_OS == "linux" || ODIN_OS == "freebsd" || ODIN_OS == "darwin" {
+when ODIN_OS == "linux" || ODIN_OS == "freebsd" {
+	SIG_ERR  :: rawptr(~uintptr(0))
+	SIG_DFL  :: rawptr(uintptr(0))
+	SIG_IGN  :: rawptr(uintptr(1)) 
+
+	SIGABRT  :: 6
+	SIGFPE   :: 8
+	SIGILL   :: 4
+	SIGINT   :: 2
+	SIGSEGV  :: 11
+	SIGTERM  :: 15
+}
+
+when ODIN_OS == "darwin" {
 	SIG_ERR  :: rawptr(~uintptr(0))
 	SIG_DFL  :: rawptr(uintptr(0))
 	SIG_IGN  :: rawptr(uintptr(1)) 
diff --git a/core/c/libc/stdio.odin b/core/c/libc/stdio.odin
index 89891f82e..4a39c22e9 100644
--- a/core/c/libc/stdio.odin
+++ b/core/c/libc/stdio.odin
@@ -2,6 +2,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
@@ -67,7 +69,7 @@ when ODIN_OS == "linux" {
 	SEEK_CUR      :: 1
 	SEEK_END      :: 2
 
-	TMP_MAX       :: 10000
+	TMP_MAX       :: 308915776
 
 	foreign libc {
 		stderr: ^FILE
@@ -76,6 +78,36 @@ when ODIN_OS == "linux" {
 	}
 }
 
+when ODIN_OS == "darwin" {
+	fpos_t :: distinct i64
+	
+	_IOFBF        :: 0
+	_IOLBF        :: 1
+	_IONBF        :: 2
+
+	BUFSIZ        :: 1024
+
+	EOF           :: int(-1)
+
+	FOPEN_MAX     :: 20
+
+	FILENAME_MAX  :: 1024
+
+	L_tmpnam      :: 1024
+
+	SEEK_SET      :: 0
+	SEEK_CUR      :: 1
+	SEEK_END      :: 2
+
+	TMP_MAX       :: 308915776
+
+	foreign libc {
+		@(link_name="__stderrp") stderr: ^FILE
+		@(link_name="__stdinp")  stdin:  ^FILE
+		@(link_name="__stdoutp") stdout: ^FILE
+	}
+}
+
 @(default_calling_convention="c")
 foreign libc {
 	// 7.21.4 Operations on files
diff --git a/core/c/libc/stdlib.odin b/core/c/libc/stdlib.odin
index 0e24b0d5c..b368c0cee 100644
--- a/core/c/libc/stdlib.odin
+++ b/core/c/libc/stdlib.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
@@ -33,7 +35,23 @@ when ODIN_OS == "linux" {
 	}
 
 	MB_CUR_MAX :: #force_inline proc() -> size_t {
-		return __ctype_get_mb_cur_max()
+		return size_t(__ctype_get_mb_cur_max())
+	}
+}
+
+
+when ODIN_OS == "darwin" {
+	RAND_MAX :: 0x7fffffff
+
+	// GLIBC and MUSL only
+	@(private="file")
+	@(default_calling_convention="c")
+	foreign libc {
+		___mb_cur_max :: proc() -> int ---
+	}
+
+	MB_CUR_MAX :: #force_inline proc() -> size_t {
+		return size_t(___mb_cur_max())
 	}
 }
 
diff --git a/core/c/libc/string.odin b/core/c/libc/string.odin
index cd577237c..c91124dcb 100644
--- a/core/c/libc/string.odin
+++ b/core/c/libc/string.odin
@@ -6,6 +6,8 @@ import "core:runtime"
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
diff --git a/core/c/libc/threads.odin b/core/c/libc/threads.odin
index 630216d06..ad305b517 100644
--- a/core/c/libc/threads.odin
+++ b/core/c/libc/threads.odin
@@ -136,3 +136,8 @@ when ODIN_OS == "linux" {
 		tss_set       :: proc(key: tss_t, val: rawptr) -> int ---
 	}
 }
+
+
+when ODIN_OS == "darwin" {
+	// TODO: find out what this is meant to be!
+}
diff --git a/core/c/libc/time.odin b/core/c/libc/time.odin
index 7cc677bff..96e80e216 100644
--- a/core/c/libc/time.odin
+++ b/core/c/libc/time.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
@@ -43,7 +45,7 @@ when ODIN_OS == "windows" {
 	}
 }
 
-when ODIN_OS == "linux" || ODIN_OS == "freebsd" {
+when ODIN_OS == "linux" || ODIN_OS == "freebsd" || ODIN_OS == "darwin" {
 	@(default_calling_convention="c")
 	foreign libc {
 		// 7.27.2 Time manipulation functions
@@ -75,7 +77,7 @@ when ODIN_OS == "linux" || ODIN_OS == "freebsd" {
 
 	tm :: struct {
 		tm_sec, tm_min, tm_hour, tm_mday, tm_mon, tm_year, tm_wday, tm_yday, tm_isdst: int,
-		_: long,
-		_: rawptr,
+		tm_gmtoff: long,
+		tm_zone: rawptr,
 	}
 }
diff --git a/core/c/libc/uchar.odin b/core/c/libc/uchar.odin
index 978d9b7bf..e49c29e51 100644
--- a/core/c/libc/uchar.odin
+++ b/core/c/libc/uchar.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
diff --git a/core/c/libc/wchar.odin b/core/c/libc/wchar.odin
index d88a49dd9..fc206e494 100644
--- a/core/c/libc/wchar.odin
+++ b/core/c/libc/wchar.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
diff --git a/core/c/libc/wctype.odin b/core/c/libc/wctype.odin
index 24af30c97..47f17e0b4 100644
--- a/core/c/libc/wctype.odin
+++ b/core/c/libc/wctype.odin
@@ -4,6 +4,8 @@ package libc
 
 when ODIN_OS == "windows" {
 	foreign import libc "system:libucrt.lib"
+} else when ODIN_OS == "darwin" {
+	foreign import libc "system:System.framework"
 } else {
 	foreign import libc "system:c"
 }
@@ -14,10 +16,15 @@ when ODIN_OS == "windows" {
 }
 
 when ODIN_OS == "linux" {
-	wctrans_t :: distinct rawptr
+	wctrans_t :: distinct intptr_t
 	wctype_t  :: distinct ulong
 }
 
+when ODIN_OS == "darwin" {
+	wctrans_t :: distinct int
+	wctype_t  :: distinct u32
+}
+
 @(default_calling_convention="c")
 foreign libc {
 	// 7.30.2.1 Wide character classification functions