diff --git a/vlib/builtin/cfns.v b/vlib/builtin/cfns.v
index ee9ca60a8d..a25dcb4096 100644
--- a/vlib/builtin/cfns.v
+++ b/vlib/builtin/cfns.v
@@ -21,7 +21,9 @@ fn C.strlen(s byteptr) int
 fn C.isdigit(s byteptr) bool
 // stdio.h
 fn C.popen(c byteptr, t byteptr) voidptr
+
 // <execinfo.h>
+// backtrace functions are not #included, that's why they have to be defined without C.
 fn backtrace(a voidptr, b int) int
 
 fn backtrace_symbols(voidptr, int)  &byteptr
diff --git a/vlib/os/os.v b/vlib/os/os.v
index 5b9fb5a6bf..03ff9a9bd0 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -791,12 +791,15 @@ pub fn on_segfault(f voidptr) {
 		return
 	}
 	$if macos {
+		C.printf("TODO")
+		/*
 		mut sa := C.sigaction{}
-		C.memset(&sa, 0, sizeof(sigaction))
+		C.memset(&sa, 0, sizeof(C.sigaction_size))
 		C.sigemptyset(&sa.sa_mask)
 		sa.sa_sigaction = f
 		sa.sa_flags = C.SA_SIGINFO
 		C.sigaction(C.SIGSEGV, &sa, 0)
+		*/
 	}
 }
 
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index be65c01d58..8276ef3226 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -100,7 +100,7 @@ pub fn (g mut Gen) typ(t table.Type) string {
 	if styp.starts_with('C__') {
 		styp = styp[3..]
 	}
-	if styp in ['stat', 'dirent*', 'tm', 'tm*', 'winsize'] {
+	if styp in ['stat', 'dirent*', 'tm', 'tm*', 'winsize', 'sigaction'] {
 		// TODO perf and other C structs
 		styp = 'struct $styp'
 	}
@@ -536,7 +536,8 @@ fn (g mut Gen) gen_assign_stmt(assign_stmt ast.AssignStmt) {
 }
 
 fn (g mut Gen) gen_fn_decl(it ast.FnDecl) {
-	if it.is_c || it.name == 'malloc' || it.no_body {
+	if it.is_c || it.name == 'malloc' {
+		// || it.no_body {
 		return
 	}
 	g.reset_tmp_count()
@@ -583,6 +584,12 @@ fn (g mut Gen) gen_fn_decl(it ast.FnDecl) {
 	*/
 	//
 	g.fn_args(it.args, it.is_variadic)
+	if it.no_body {
+		// Just a function header.
+		g.definitions.writeln(');')
+		g.writeln(');')
+		return
+	}
 	g.writeln(') { ')
 	if !is_main {
 		g.definitions.writeln(');')
diff --git a/vlib/v/gen/cheaders.v b/vlib/v/gen/cheaders.v
index 52ec306323..94deb93e4b 100644
--- a/vlib/v/gen/cheaders.v
+++ b/vlib/v/gen/cheaders.v
@@ -190,6 +190,7 @@ int load_so(byteptr);
 void reload_so();
 void _vinit();
 void _vcleanup();
+#define sigaction_size sizeof(sigaction);
 
 // ============== wyhash ==============
 //	Author: Wang Yi
@@ -311,6 +312,7 @@ typedef byte array_fixed_byte_400 [400];
 	#define true 1
 	#define false 0
 #endif
+
 '
 	bare_c_headers = '